|Mediterranean Garden Society|
Container gardening – what plants to grow and how to care for them
Many mediterranean gardeners do not have the luxury of a plot of land for a garden and are confined to growing plants on a balcony, paved yard or a roof terrace. For them container gardening offers plenty of scope and pleasure. There is a multitude of plants which will grow successfully in pots, mostly the sub-tropicals like Hibiscus rosa-sinensis (Chinese Hibiscus) from Asia and Brunfelsia pauciflora (Yesterday, Today and Tomorrow) from Brazil. But some true mediterranean plants can survive quite happily and many of the native bulbs can be enjoyed each spring if kept in pots. Even those of us with gardens will usually have some potted plants – things a bit tender perhaps which need to be moved to a protected place in the winter, or rather special plants which we are afraid might get lost in the beds.
In a recent talk to the Greek Branch, The Mediterranean Garden editor, Caroline Harbouri, provided answers to all the practical questions you might have about container gardening and included a list of tried and tested plants for pots.
Caroline has been recording her experiences as a container gardener in the Journal for the past eight years and her articles are reprinted below.
Gardening in Pots on a Roof in Central Athens
Pot Plants and the Saw
Some Salvias Grown in Pots
Another alternative is to concentrate on cacti and succulents which require a different kind of care in a mediterranean climate.
Notes on growing cacti and succulents in containers
Cactus on a Corinth Balcony
Small Aloes for Pot Gardens
The basics of container gardening in a mediterranean climate are pretty much the same wherever you do it Caroline Davies’ article from Australia mentions a different selection of plants:
Gardening in Pots in Melbourne
Growing citrus trees in containers in climates where they cannot be grown outside year-round is a well-established practice, but if you want a tough citrus try kumquats. Vegetables can also be grown successfully in a small space.
‘Quats in Pots
Finally how to attract wildlife:
Wildlife Gardening for Balconies and Gardens
Good shrubs for pots in sunny positions:
In shade you can grow various ferns and fuchsias. In semi-shade try Jasminum sambac, either single- or double-flowered.
Where space is limited on a terrace, climbers are a great solution, grown on wires or trellises:
Don’t forget annual climbers, easy to grow from seed. The following can usually be found in garden centres:
Regular dead-heading encourages prolonged flowering in many of these plants.
Don’t forget small winter- and spring-flowering bulbs, which can be left dry in summer, with their pots perhaps moved to a shadier corner and protected from cats.
Also many kitchen herbs: mint, chives, parsley, chilli etc.
Many typically Mediterranean plants such as lavender are not well suited to cultivation in pots. In their natural habitat they develop deep woody roots in order to survive the summer drought and do not need or want water. The restriction of a pot prevents the plant from making its deep roots. No plant in a pot can survive the summer unwatered, so for those plants that don’t want water it is hard to find the right balance – giving just enough for the plant to survive but not enough to kill it.
Having said that, it is always worth experimenting with any plant that you’d really like to grow…
In her article on gardening in pots in Melbourne (TMG 43 see below Ed.), Caroline Davies quoted Julie Lake’s claim that “If it can be grown in the ground, it can be grown in the pot”. I’m not sure that I quite agree with this optimistic statement – after all, what about big trees? Yet when I moved in 2005 to the centre of Athens, where my ‘garden’ consists only of a roof terrace and a tiny tiled courtyard, I decided that it was at any rate a good principle to start with. Time and experience would show me what I could and couldn’t grow in pots.
I had always grown some plants in pots on the balcony of our old house, among other things Hibiscus rosa-sinensis, for example, and a few hybrid cannas. The former would not have survived the winter outside and needed to be brought into the house to over-winter in an unheated room (I once discovered that I’d inadvertently brought in a small green tree-frog with the hibiscuses, who luckily didn’t seem to have come to any harm). The latter were the result of a marital compromise: my husband loved cannas and, having pronounced sniffily, “They wouldn’t suit the garden, we are not going to have cannas,” I reflected that this was ungenerous and suggested, “We can have a couple in pots on the balcony if you like”. And in fact they did perfectly well in pots, though requiring fairly frequent division, and somehow the bright colours and dull, municipal-park stiffness which (for me) disqualified them from being planted in the garden seemed not to matter at all on the balcony. Today, in memory of Spyros, I still have several of his cannas on my roof terrace and find that they blend quite successfully with the other plants. This has led me to recognise that the aesthetics of pot-gardening and garden-gardening differ.
Perhaps it is that we expect different things from our potted plants. A mature garden, even a small one, has trees and a background or perspective; we can enjoy this without demanding constant flowering. A pot garden on a roof such as mine has, by contrast, no trees – and hence no shade and not much variation in the intensity of the light – and its background consists mainly of other people’s roofs, solar panels, washing lines and satellite dishes. (I count myself lucky that one of my neighbours has a mulberry tree in his courtyard, whose dark green foliage provides a restful and cooling backdrop on one side throughout most of the year.) Moreover, shrubs grown even in large pots cannot attain the full stature that they would have in the garden. As a result, it seems to me, a ‘garden’ consisting of pots cannot rely to any great extent for interest on the architecture of the plants or the play of shapes and forms. What this means is that one tends to count more on flowers and on foliage.
As I began to learn what would do well in pots in my extremely sunny and exposed conditions, I thus disciplined myself to discard plants which I felt were not earning their keep. It is not that I expect everything to be in permanent flower; on the contrary, I am perfectly content with the relatively brief spring flowering of, for example, Iochroma australe (which I grew from seed more than ten years ago when it was called Acnistus australis) and Brunfelsia pauciflora, commonly known as Yesterday Today and Tomorrow, because both of them produce their flowers generously and for the rest of the year make quietly pleasant green masses. But Lycianthes rantonnetii (formerly Solanum rantonnetii) had to go, much as I loved it in my old garden for its August flowering when so much is dormant: in a pot its flowers were simply too sparse. Caryopteris × clandonensis had to go too, although Caryopteris incana is happy, flowers well in late summer and seeds itself cheerfully into other nearby pots.
‘Nearby pots’ is a key phrase. Plants which if placed singly in widely spaced pots would probably struggle to survive in baking summer temperatures, with full sunlight from 8 in the morning until sunset, flourish when they are closely packed together. Each plant provides a little shade for its neighbour and together they create a small humid microclimate. It is true of course that my plants are massed three deep partly because I have a lot of plants and little space; true, too, that I happen to like plants growing into and through one another, for example a white Lantana camara and a darker-coloured cultivar of Duranta erecta intermingling in front of a white Lagerstroemia indica. But the fact remains that this close proximity suits plants grown in pots in hot and sunny positions. (I should add in parenthesis that Lantana does well in a pot and certainly earns its keep: I have four plants of L. camara – including two white ones – on the roof terrace and two L. montevidensis – one white and one mauve – in the courtyard and, provided that they are dead-headed regularly, all flower for months on end.)
Close proximity, however, while beneficial in summer, is not necessarily so in winter. Since there is not much space to move the pots further apart, I tend to do quite a bit of pruning and cutting back in winter in order to allow more air to circulate between the plants. Close proximity also means that any insect infestation is likely to spread rapidly; here too my solution is simply to cut off and destroy the affected shoots, and so far this has always worked, even with a leaf-curling blight that began to affect the lemon tree.
One of the great advantages of having one’s plants in pots is indeed the fact that it makes it easier to check them individually day by day and to respond immediately to any problem. At night one can do regular snail and slug patrols with a torch. And early on summer mornings, before the sun has reached my terrace, it is always a delight to drink my first cup of coffee there, to contemplate the plants and consider which of them may need attention.
I prefer watering by hand – once again, one can give each plant exactly what it needs – but nevertheless I have a drip irrigation system as a fall-back or for when I go away. In summer I place saucers under most pots so that they can drink their fill; however, in autumn I remove the saucers to prevent the earth in the pots from becoming sodden when it rains. I usually cover the surface of the soil either with large pebbles alone or with a layer of gravel and then large pebbles (gravel by itself would be fine for the plants but does not deter visiting cats).
It is precisely because of these cats that I have a problem growing bulbs in pots, particularly small bulbs. The difficulty is that the large cat-proofing pebbles are too big and heavy for the emerging shoots, while my other cat deterrent – sharply pointed wooden kebab skewers stuck into the soil around the plant like an aggressively bristling hedgehog – can only be put in very carefully when the bulbs are in leaf, for otherwise one risks skewering them. When the bulbs are dormant in summer and their pots unwatered, I’ve found that the best solution is to tuck them away in a discreet corner with a strong plastic mesh over them weighted down by stones. But the result of all this, since my space is limited, is that I grow far fewer bulbs than I’d originally intended.
Another lesson I have learnt is the importance of a plant’s position: a mere metre in one direction or the other can make a significant difference to the amount of heat and light it receives. I’ve said that one can’t very well grow trees in pots, but in fact I do have two: a lemon tree and a small Ginkgo biloba. These are both in the courtyard rather than on the terrace since, unlike the terrace, part of the courtyard receives a bit of shade in the late afternoon. The lemon tree is happy where I put it and hasn’t been moved. The ginkgo, however, was leaning at a slight angle where I didn’t quite want its branches; I thus thought I’d make it lean in the other direction and turned the pot round by 180 degrees. This was disastrous: within a few days the leaves became badly scorched and browned by the sun. I thus hastily turned it back to its original orientation, realising that the ginkgo knew what suited it best, whereupon it promptly recovered. Similarly, I thought my Clematis armandii would look lovely growing over the grille of the kitchen window, facing west. I was quite wrong: it suffered desperately. I replaced it with a Thunbergia grandiflora which loves the heat and sun and moved the clematis to the other side of the courtyard, to an east-facing position where it is now twining happily up the spiral stairs that lead to the terrace, in company with a Maurandya (syn. Asarina) scandens – a successful combination since they flower at different times. One of the advantages of growing plants in pots is that if you make dreadful mistakes in the position you’ve chosen for them, you can always move them easily.
Another recognition: plastic pots are lighter than terracotta pots. I very much prefer terracotta pots of the plain, classical variety and had never imagined that I’d ever grow anything in a plastic pot. But I’ve had to learn to be realistic and accept that on a roof terrace weight matters. Thus most of the plants on the terrace are now in plastic pots, although at ground level, in the courtyard, the pots are all good terracotta ones. Changing from terracotta to plastic is a little bit like learning to cook on an electric stove when one is accustomed to a gas stove. I’ve found, for example, that plastic pots need even greater attention to drainage than their terracotta counterparts since they don’t ‘breathe’ as terracotta does. I don’t much like the look of plastic – it’s a visually flat and ungiving material – but at least with the plants closely massed together not too much pot is visible.
I am still learning, still experimenting, still finding out what I can and can’t grow. But I was heartened when the woman in my local photocopy shop said to me recently, “I do like your garden.” I’m not sure where she lives but obviously she can see it from her windows. My terrace gives me so much pleasure that I’m glad if it is giving pleasure to others too.
I have come to the conclusion that, after secateurs, my curved gardener’s saw is the most useful garden tool that I possess. In the old days when I had a garden I never gave it much thought, using it only occasionally to remove small branches that were too substantial for secateurs; now, however, that I grow all my plants in pots the saw has truly come into its own.
For plants that can be divided, the solution is easy. Salvia madrensis, Salvia leucantha, Clerodendrum floribundum, day lilies (Hemerocallis cultivars), my late husband’s cannas, Tulbaghia violacea, Epilobium canum, Hedychium coronarium, Dicliptera sericea (syn. D. suberecta)and many other plants can be hauled out of their pots then pulled or chopped to pieces, some of which are replanted and some given to friends. (One of the plants I treat like this is my very oldest plant – a Michaelmas daisy-type aster, name unknown, of which a small root was given to me in 1974 by my old cleaning lady, Athanasia. In autumn it produces a profuse haze of tiny white flowers on delicate, tall, airy stems. I certainly didn’t want to say goodbye to this plant when I left our old house and garden so grubbed up another small piece and brought it with me to the centre of Athens, where it does perfectly well in a pot, having now given me 37 years of faithful understated beauty). For large plants that can’t be divided, however, something more drastic becomes necessary.
So out comes the saw… Once again I heave the plants out of their pots. And a word of warning here: unless of course one is prepared to break the pot, it is well-nigh impossible to get a large plant with its roots intact out of a rounded pot that bellies out in the middle then narrows at the top – which is why all my pots are always the usual regular flowerpot shape, narrower at the bottom and broader at the top: whoever first came up with this design in the distant past certainly knew what he was doing. Having got the plant out (preferably on a tarpaulin to reduce the mess needing to be swept up afterwards), I saw off the lower third of its roots, straight across, quite mercilessly. From time to time the saw will encounter some of the broken terracotta shards that were originally at the bottom of the pot for drainage; these I prise out with my fingers. I’m always impressed by the power of growing plants, and not least by the way after a couple of years the roots have sometimes pulled these drainage shards almost half-way up the pot. I then replace the plant in its pot with fresh earth, and finish by pruning off up to two-thirds of its top growth. This procedure I carry out in winter, aiming to treat all large shrubs in this manner every two to three years. Naturally, I don’t always do everything I aim to do, and thus there are quite a few plants on the waiting list for this treatment.
What to do with the old soil shaken off the amputated roots was a question that at first exercised me, for although I didn’t want to re-use it in my pots I really balked at the idea of throwing away earth – from which comes all life – as if it were rubbish. In the end I decided to carry it up the road and scatter it on the surface of the soil in a rather sympathetic little area of long-established municipal planting – an acacia tree, a large old Cestrum elegans (syn. C. purpureum), a Duranta – where sooner or later it will be enriched by fallen leaves and incorporated into the ground.
All the shrubs which I’ve submitted to this major root pruning have responded well. Those that underwent it in winter 2010-2011 include a white-flowered Lantana camara, a white-flowered Lagerstroemia indica, a Duranta erecta, a Cestrum nocturnum, a couple of Hibiscus rosa-sinensis and an oleander on the terrace, as well as an Iochroma australe in the courtyard. The Iochroma, which hadn’t been repotted since 2005, had started to look a bit sparse so that I was beginning to worry about losing it; however it is now lush again and flowered well in May. The Cestrum nocturnum seems to be slightly slower to flower this summer – though it’s beginning to do so now – but overall looks dense and green and happy. The difference between the white lantana and an untreated yellow lantana of similar size and age beside it is striking: the root-pruned plant has larger, dark green healthy-looking leaves and many, many more flowers, while the untreated plant has fewer, smaller and somewhat paler leaves and fewer and smaller flowers, which moreover seem to last less long. Needless to say, this yellow lantana is the first candidate for the tough root-sawing regime next winter, along with several more oleanders, two brugmansias, a Cestrum elegans, possibly a Justicia carnea (but maybe this can wait until the following year) and a 15-year-old Erythrina crista-galli. The latter I prune back to the wood every winter anyway as its top growth tends to die back, so it won’t need anything more than root pruning.
I hit on this idea of root pruning after worrying away about what to do with pot-bound plants that were already in the largest pots my terrace could cope with. Recently, however, Fleur Pavlidis pointed out to me that this is the treatment that has been given for centuries in Italy to lemon trees grown in pots in order to be moved under shelter in winter – and presumably to all those lemon and orange trees once grown in grand orangeries throughout northern Europe, and probably to their oleanders too for that matter. “But of course,” I exclaimed, “yes, now that you remind me, I did know that”, realising that without doubt this knowledge had been lurking somewhere at the back of my mind, ready to come forward as a solution when needed. Most practical, effective gardening techniques and solutions were worked out long ago by our forebears – generation upon generation of nameless, unsung and talented gardeners.
My handy little saw has other uses too. I am always irritated by the way nurseries graft oleanders, so that often when one thinks one is buying one colour one ends up with a different colour altogether as the stronger rootstock on to which the desired colour has been grafted gradually takes over. This happened to me when a desired pale yellow oleander produced an ever more vigorously growing undesired pink-flowering half. As Kate Marcelin-Rice noted in TMG 57 (‘Gold and Silver’), yellow and pink are not colours that look good together. “Kill or cure,” I said to myself and got out the saw. I turned the oleander out of its pot, traced the two sides of the plant down to the swollen graft, just above the soil level, and started sawing it vertically in half. Oleander wood, as I discovered, is dense and hard. I sawed and sawed and sawed and sawed… until my cleaner’s husband came along, took one look, said “Here, give that saw to me,” and finished the job in five minutes (I had, however, got more than half-way). I sliced through the roots, repotted the yellow half, gave away the pink half and waited to see what the result would be. And the result is that I now have a flourishing pale yellow oleander, growing on its own roots, without a trace of its erstwhile pink partner.
My saw is indeed a valuable tool that I cherish.
For the last five years, since leaving my old garden, I’ve been experimenting to find out which plants I can grow most successfully in pots in the hot and sunny conditions of a roof terrace in central Athens. My criteria for success include not only whether a plant will survive for any length of time in a pot, but whether it is almost as floriferous in a pot as it would be when planted out in the ground. The genus Solanum, for example, doesn’t seem to meet the second criterion very adequately. The climbing Solanum crispum thrives and flowers well enough; what used to be called S. rantonnetii (now Lycianthes rantonnetii), however, I got rid of by giving it away, since having been accustomed to its profuse flowering in my former garden, I couldn’t be doing with its meagre performance in a pot; and the fate of S. laciniatum is hanging in the balance while I make up my mind about it. I’m tempted to give the very tender climber S. wendlandii a try in a protected corner – if I can get hold of it – on the principle that if one climbing solanum does well, then another might too.
By contrast, the salvias that I grow have all delighted me.
Salvia coerulea (syn. S. guaranitica)
Salvia × jamensis
Salvia officinalis subsp. lavandulifolia
I grow three other salvias but have not listed them here since I haven’t identified them yet (oh how tiresome nurseries are when they sell unnamed plants…). One is a small-leaved white-flowered plant with something of the twiggy habit of Salvia microphylla although its leaves are not aromatic); one resembles S. microphylla in leaves and form and has microphylla-type flowers, though slightly larger, that are somewhere between ivory and very pale creamy yellow; and one is a tough-looking plant with wiry stems and small purple flowers.
More photographs of some of the above salvias growing in the MGS garden at Sparoza can be found here.
Notes on growing cacti and succulents in containers
Watering container-grown cacti and succulents
Water is of course vital to the survival of cacti and succulents grown in pots, but it is also one of the main reasons for their loss. In their natural environment cacti and succulents are adapted to resist long periods of drought and can find enough moisture from a single rainfall or even from the humidity in the air to maintain life, grow, flourish and multiply. Nature cannot be replicated however when they are cultivated in pots, indeed the plants become more sensitive and vulnerable to adverse conditions and diseases, so the gardener must be extra careful and observant. Watering is essential but excessive water can easily lead cacti and succulents to rot or crack and so die.
Many cacti must stay completely dry during the winter. When the plant shows signs of growing in the spring it is time to start watering, but very slowly at first so as not to cause a shock which can cause rotting. One way to avoid shocking delicate cacti is to start by using a water spray only and then slowly increasing the amount of water and frequency until by the summer a weekly watering is given. Of course there are always exceptions such as Astrophytum, Ariocarpus, Copiapoa, Aztekium, Lophophora and generally the more susceptible cacti which need less water than other plants and should be watered only every 15 days or even less frequently.
There are a multitude of different species of Astrophytum, each
The genus Uebelmannia prefers to continue being sprayed rather than watered, while grey-coloured Copiapoa (e.g. C. cinerea) should be watered once every three weeks and then only very lightly.
Cacti with nodular roots such as Leuchtenbergia, some Mammillaria, Pterocactus etc. must be watered with care approximately every 15 days because there is a particular risk of their roots rotting.
Tropical cactus like Hylocereus, Epiphyllum, Schlumbergera, Selenicereus, etc. may need additional water given by sprays on the upper part of the plant on very hot days.
Succulents need more water and during the summer can be watered twice or three times a week depending on the heat, shade, pollution etc. Some succulents, especially those with tuberous roots, need little and often as a watering schedule.
Dioscorea must be watered once every 20-25 days, even during the rest period, to maintain their roots.
Repotting container-grown cacti and succulents
Soil for potting cacti and succulents
Choosing a soil mix for potting cacti and succulents is quite complicated. Every expert you ask and every book you read will have a different opinion. However there is one basic requirement for any soil mix: it must have such good drainage that it will have dried out within a day or two of watering. Within that time the plant can absorb as much water as it needs to survive the next waterless 7-10 days with the strength to grow and to flourish.
Components of the soil mix can be: sand, perlite, a little leaf mould, a little peat, red soil, pumice stone, broken shells, cuttlefish bones, various Japanese soils such as Akadama, Kanuma, Kiryu and many others. There is ‘cactus soil’ available commercially which consists of purified peat, leaf mould and wood waste. A simple and quick mix for all succulents and cacti is ready-made commercial cactus soil mixed with perlite and sand. On the other hand combinations can be concocted to suit each type of plant.
For sensitive species like Aztekium, Geohintonia, Lophophora, Obregonia, Strombocactus, and some hybrids of Astrophytum, again the soil mix must have excellent drainage. A mix for these plants can contain a little ready-made cactus soil, fine perlite, pumice, Kanuma, Kiryu, Akadama, lava, scallop shells and cuttlefish bones.
Some tough cactus and succulent species like Cereus, Opuntia, some Agave and Aloe have no special requirements in soil and can be planted in any blend and type of soil.
Most of the plants on our balcony have been collected from neighbours’ gardens and pots, or even sometimes as the odd reject from the rubbish bin, with the result that I hadn’t a clue how to look after them when they first arrived, quite ignorant of whether they needed sun or shade, watering or not. I must have been doing something right, however, as the plant which I believe to be Echinopsis oxygona has presented me with a good crop of flowers this summer.
For a couple of years it produced no flowers at all. This year I moved it into a sunnier position, whereupon it rewarded us with a first crop of flowers in May and the last ones in late August. In between there were one or two solitary flowers. The flowers are 20cm long and 10cm wide. The petals are quite a dark pink when closed and a very delicate pink when open. As the flower only lasts one day, the pot is lifted on to the balcony table for that day; neighbours are invited in for coffee and everyone is instructed to go and admire it.
The plant is in an ordinary pot 26cm high and 28cm wide. A few years ago I put it into a wide ceramic dish, thinking that as a cactus it did not require so much soil; however, the plant did not seem to flourish and I thus potted it again into a deep pot.
As far as watering is concerned, all the plants on my balcony have the same fate: once a week in winter if it doesn’t rain and every few days in summer (with the occasional two-week drought if we go away on holiday and the family forgets to water the plants). All our plants are in a mixture of earth from various sources and none gets any special treatment in that department. My balcony here in Corinth is roughly south-facing with a lot of sun from mid-morning until sunset. We are only one block from the sea so there must be large quantities of salt spray when the wind blows, though it doesn’t seem to bother this particular cactus. In the spring I give it a dose of the blue fertiliser which farmers here use for their trees (Axion N12-P12-K17, magnesium, iron). The winter of 1999-2000 was a very cold one in Greece but this robust cactus did not suffer any damage. Possibly it may have been sheltered by the balcony wall.
Gardeners everywhere endeavour to find ways to continue their contact with the green and living world, even as climate change brings about altered conditions that impose new boundaries and the prospect of growing fewer of the plants we enjoy brings its own feelings of loss and sadness.
To cheer myself up, and to encourage others too, I have been looking back to our forebears’ practice of growing collections of potted plants. I recall several ancient aunts who gardened in the era before tapped water supplies were available. …they kept potted plants at the back doorstep, and perhaps on the front veranda too. While we still see some of the old stalwarts – cane begonias, Kentia palms, rough maidenhair ferns, sword ferns, hippeastrums, tiger lilies and oriental lilies, sprekelias and vallota lilies –, by and large the bulk of their favoured hardy pot plants are now scarcely known. Principal among this group of under-appreciated plants are the small-growing succulents, and the dwarf aloes in particular.
Generally very affordable, they look best planted in shallow, broad pots clustered in groups of three to five – but ensure that there is room left for the plants to increase by natural off-setting. A layer of small gravel or pebbles over the surface of the potting soil looks attractive and offers an extra degree of drainage around the rot-sensitive crown where the thick succulent roots join the rosettes of succulent leaves. Children visiting our garden brought faded, worn sea-shells to add a fairy garden to the display. They showed great interest in the curious plant forms – the bristles and ‘soft’ spines, the ‘babies’ appearing around the base of each mature rosette and the fat seedpods that developed on some stems. Plants placed in a partly shaded setting on a terrace or patio will attract honey-eating birds when they flower in winter, giving the endless pleasure of watching them as they hover above the nectar-dripping flowers.
A brief over-view of this small group of clustering plants might serve to encourage mediterranean gardeners to add these little treasures once more to their gardens, either as pot plants or as inhabitants of rocky places where there is some shelter from the full force of the summer sun at midday.
To my haphazard way of thinking about things, it seems handy to progress from the most frequently found to the more infrequently seen species. All the species described here form small low-growing rosettes that are usually regarded as stemless; many remain solitary for a good many years though eventually long-matured plants will produce offsets. Only the brave-hearted will contemplate inducing multiplication by mutilation of the central growing point, but it is by this means that new side growths can be stimulated into appearing – eventually. As a general guide, these plants require free-draining soils, whether grown in the garden or cultivated in pots. That is, they do not tolerate badly drained sites or soils. In the wild many are found on gently sloping hillside habitats growing among rocks and gravels, or in sandy tracts. Such soils may be highly mineralised but are low in nutrients so aloes do not need much fertilising to maintain growth. Indeed, plants fed too well and watered will grow uncharacteristically lush and soft, losing their attractive compact forms and colourings, and running the risk of rotting. No aloes like living in deep shade but many of the smaller kinds such as these grow in the shelter of sparse thorny bushes and dead winter grasses. They can be grown in full sun but care needs to be taken to ensure that the plants do not suffer from sun burn and leaf scorch as this ‘cooking’ can also induce rotting. Only one aloe, Aloe polyphylla, grows where there are regular snowfalls; all the rest have varying degrees of frost and cold resistance. Careful observation will indicate which kinds need the shelter of a porch, windowsill or cold greenhouse in winter, as much to keep them on the dry side as to safeguard against freezing.
Aloe aristata forms an open rosette of dark green leaves with white spotting on all the leaf surfaces and small bristles along the leaf margins, hence its common name of Lace Aloe. In dry weather the rosettes will close up somewhat, the outer leaves and also the leaf tips drying up. This aloe produces offsets freely so that solitary plants quickly form clumps. Its mid-winter flowers are red and borne in short spikes that are sometimes candelabra-like in mature plants. Propagation is mostly by removing offsets and growing them on as separate plants. Root formation is readily achieved.
Aloe humilis is readily recognised by its silver-blue leaves, almost cylindrical in cross section, tapering narrowly at the apex and also slightly incurving. Each leaf has regular but well-spaced prominent coarse white teeth along the leaf margins and also along the mid-rib of each leaf. Its flowers generally appear a little later than those of Aloe aristata and are also red. I have never observed branched flower stems. Propagation as for Aloe aristata.
Aloe variegata, the partridge-breasted aloe or triangular aloe, is instantly recognisable by its characteristic triple file of thick upright leaves. Each leaf is margined in white and has no conspicuous teeth or bristles, but the leaves are spotted and banded with white markings. Mature plants produce branching flower stems in winter with numerous red-tubular ‘bells’. Plants prefer a soil that is very well drained and are at risk of rot if not given such conditions. My own plants appear to flower intermittently over the winter, being neither early nor late but making their appearance somewhat haphazardly. Offsets are produced sparingly and slowly so propagation by seed is often the preferred method of increase.
Aloe melanacantha is a relative newcomer alongside the three old familiars above. Aloe melanacantha is recognisable by its deep green, broadly triangular and relatively thin leaveswith dark brown ‘black’ spines on the leaf margins and down the back ridge of each leaf. Individual rosettes tend to be larger than those of the above-mentioned aloes and may attain an eventual diameter of 20-25cm. Again, winter flowering is the norm and the tubular and somewhat campanulate flowers are also red; flowering occurs when plants are mature, around 5-7 years from seedling stage.
Aloe longistyla is almost an endangered species in its habitat around the Great and Little Karoo deserts; it hangs on despite over-collecting and over-grazing but seeds are readily available from captive breeding collections and hence to specialist nurseries around the world. It is a very appealing little plant superficially resembling Aloe humilis until flowering time, when it shows its distinctive brush of orange-red flowers with markedly exerted styles. Probably considered rare by succulent collectors, it is nonetheless becoming readily available and very affordable thanks to the conservation efforts of captive breeders in South Africa.
Aloe peglerae is another plant considered until now a collectors’ rarity. Carefully controlled intra-specific breeding is rescuing a species critically rare in its habitat around Witwatersberg and Pretoria. Endangered by changing land use and increasing population density, this species deserves a wider appreciation among gardeners in summer-dry climate regions of the world. Characteristically it has tightly incurved clusters of grey leaves which form solitary plants from which emerge dense spires of pendent floral tubes of bright red changing to yellow as the flowers open. It is not hard to grow as long as the soil is well drained. Spination is largely confined to the leaf margins and the back ridge of the leaves towards the apex. Individual leaves are broadly triangular and rather elongated.
Aloe pratensis is not so widely grown but is worth looking out for. It has potential as an attractive and compact aloe, especially for rock-strewn sites and soils where it is at home growing in cracks and crannies. Native to Kwa-Zulu Natal and the Drakensberg mountains, it is noteworthy for the papery white bracts that cover the densely packed emerging flower buds. The numerous pinkish-red flowers may still be opening atop the stem when the lower, fertilised flowers develop mature fruits. Plants form small clusters of six or so rosettes, each one bearing silver-grey leaves with prominent brown marginal teeth and spines on the undersides.
Aloe krapohliana, hailing from the very arid mining region north-west of the Cape of Good Hope, is as attractive as it is poorly understood in cultivation. Endangered in its habitat by mining leases, over-grazing and over-collecting, it presents challenges to would-be species rescuers because it is very susceptible to too much rain and/or too much watering. Growing in dense clusters of up to 16 or so greyish-green rosettes, it is distinctive for its minimal spination, minute and barely present except along the leaf margins. The flower spikes, large in comparison with the size of the plant, are densely packed with dusky red flowers. A lovely plant but so far hard to obtain if you can’t buy it from the locals making pocket money along the roadsides.
Aloe × ‘Tegelberg’s Triumph’ is a hybrid of recent origin that is well worth seeking out. It appears to be a child of Aloe aristata and Aloe erinacea (now regarded as a white-spined form of A. melanacantha) but who was Tegelberg? It is a mountain in the Schwangau region of Bavaria so maybe the name is a reference to this ‘family-friendly’ (according to the local tourism association) recreation site. However this may be, the solitary rosettes of narrow, thin, incurving green leaves are densely covered with fine white teeth and bristles along the leaf margins and on the leaf surfaces. They are quite attractive and distinctive too. The old leaves turn papery and silvery as they age and dry out, while the leaf tips take on the appearance of being white-awned as they become dry. Flowering seems a little sporadic but the short spires of red, pendent tubes make a nice contrast to the whiteness of the leaf markings, teeth and bristles. The closely-packed leaves can be susceptible to rot induced by winter rains standing too long in the crown of the plant. Propagation is by the very occasional basal offsets or by careful mutilation of the growing centre of the plant, after which new growing points may develop in time.
Caroline describes container gardening in a small, town house garden to which she moved in in 1999, seven years before writing the article:
On moving day, we required a special truck to transport our pots and troughs – these had accommodated plants which did not fit into our previous garden and were used as accent plants or eye-catchers (such as a large bay tree, a bronze-foliaged cordyline and a Wigandia urens (syn. W. caracasana) which suckers too much for a city garden), as well as delicate plants which we preferred to nurture, particularly small bulbs, cyclamen, auriculas and lewisias, and an assortment of bowls with succulents.
At our new home we intended to extend this pot collection to create an attractive garden (which we could control) and to satisfy my love of plants. We were influenced by the pot gardens we see in Greece, whether in Crete, Corfu, Parga or Delphi where pots are often arranged on different levels, filling flights of steps, ledges on walls and windowsills. David, my husband, salvaged concrete bricks from building sites to build rising platforms which were capped with old slate hearth stones, rendered and painted Venetian pink. We have allowed them to crumble and fade, resembling the pink stucco on old Venetian villas in Corfu. The pots set high in this part of the garden complement the massed arrangements at ground level, as do the plants on the mosaic tables and Victorian plant stand, painted Grecian blue.
In her book Gardening in a Hot Climate (Lothian Books, 1996), Julie Lake states: “If it can be grown in the ground, it can be grown in the pot!” I completely agree with her, with the one reservation that, eventually, some plants will get too large and will have to be dealt with drastically or given to a new home.
Our variegated form of the Australian native Dianella tasmanica came from Rachel Howell (Rosevears, Tasmania) a number of years ago before it was stocked by general nurseries. She grew it from seed acquired from Scotland and it is a particularly strong form. We had many years of enjoyment from this dianella with its variegated strappy foliage all year round, more important than the flowers and berries which are less prolific than on the normal form. Last year my plant (which had been repotted over the years) was still flourishing and growing in a pot that had cracked from the extent of growth. Rather than obtain an enormous container for this plant, we divided it – with some considerable effort… Three-quarters of the dianella went to my brother-in-law’s garden near Hanging Rock in the country; the remainder was potted into three largish containers, two of which make beautiful contrasts with green foliage around them in our back courtyard, while the other is now in my brother’s garden in Balwyn.
Looking at our garden, I am aware of at least two plants which are thriving now but will require attention next year. The first is a large Astelia chathamica (silver sword-shaped leaves) which was placed to complement the rough-hewn stone water sculpture by Jock Langslow (grandson of the famous Australian artist Sydney Nolan). The astelia has flourished considering that it was bought in a tube from the Garden of St. Erth four years ago. The Phormium cultivar ‘Yellow Wave’ was a quarter of its size when we placed it in an ancient stone trough a few years ago. We chose it for its weeping form so that it would not obscure the wall plaque above of a maiden with a thyrsus (a long fennel stalk topped by a pine cone, carried at ceremonies of Dionysos, the Greek god of wine), but it is now expanding – too rapidly – at the lower levels.
Both these plants are from New Zealand and thrive in the back courtyard which faces south and is never too hot in summer. There is little sunshine in winter, but adequate light. For this reason I grow many hellebores which are undemanding (but they do need a deep pot) and have the advantage of attractive foliage as well as a long flowering season in the colder months. In this category are the species cyclamen in smaller pots, with intricate variations in their foliage and free-flowering character. Some flower in winter/spring, others in autumn, and most need a dry dormant period, so they can be hidden away, protected from the hottest sun.
I have always grown a range of succulents and cacti, loving the architectural form of agaves, aloes, furcraeas and puyas (despite their vicious spikes). Until recently, we were proud of our Puya alpestris (acquired from Mt. Tomah Botanic Garden in 1998), which graduated to a spot on our front wall where it could no longer harm us as we moved through the front courtyard. Only a masochist would try and steal it – or so we thought. It disappeared on New Year’s Eve (during the day) when David and I were walking in Sherbrooke Forest!
I do prefer to mix succulents with contrasting softer foliages, flowers and conifers, rather than growing them on their own, although in winter I have the majority in the front garden with the sunshine. Some I use as a dramatic feature, such as Senecio jacobsenii, which spills out of a mosaic wall planter and turns a rich dark red, picking up this colour in the mosaic work.
Succulents vary enormously and it takes time to learn which ones can tolerate the hottest sun or need shade in summer. As Rudolf Schulz and Attila Kapitany say in their useful book Succulents: Care and Health (Schulz Publishing, 2003), most succulents are killed by under-watering. They have gained a “low maintenance” image but they do need regular repotting, fertilising and watering in warm weather. Here in Melbourne, they are prone to various attacks – by blackbirds, snails, slugs, caterpillars and mealybugs, to name a few culprits – and can be devastated by a hail storm or excessive rain in winter.
When looking for plants for pots, we are most influenced by foliage. Flowers are an additional bonus in the case of our cannas, with structural bronze leaves remaining all year (in warmer winters than the one just passed). I would also grow Hedychium greenii – the spectacular ginger lily from Bhutan with reddish stems bearing deep green leaves, purplish-red beneath – even if it did not produce its bright red flowers. This plant regularly grows too large for its container, but new ones are easily propagated from bulbils formed in the leaf axils. In the same way, I grew our enormous Furcraea foetida (syn. F. gigantea) from a small bulbil picked up on the lawns of Melbourne’s Royal Botanic Gardens some nine years ago.
Easy propagation from cuttings is a bonus of the shrubby begonias, of which I have a few. Once they become too large, their progeny are waiting in the wings. These plants can become as addictive as succulents. Garden writer Sarah Guest started this process when she gave us our first stem cutting years ago, just as the handful of houseleeks she gave us even earlier initiated our quest for succulents.
We were introduced to the toughness of vireya rhododendrons in pots by Jenny Walker, who had her nursery in High Street, Prahran, for many years until early in 2005. Most of these rhododendrons grow as epiphytes in their native habitats, which means that root confinement in a container is no problem at all. They can flower up to three times a year – often at different times in different years, so there is no predictability… This year, ‘Pindi Pearl’ began to flower in early June and its scented flowers have continued in abundance through September. ‘Cristo Rey’, which was bred in Wollongong, New South Wales, has its own microclimate in our front courtyard. The giant Burmese honeysuckle grows strongly in the hot summer months to shade it from the hot sun. We cut back this vigorous climber in winter, ensuring maximum light for a profusion of bright orange flowers to follow. The easiest vireya of all for us is ‘Coral Flare’, as it is low-growing, not too heavy to move from sun to shade, from one season to another, and it always appears to have a flower or two.
Finally, plants with associations are very important to us. We grow plants we have seen in the wild in Greece, tracked down at specialist nurseries such as Marcus Harvey’s “Hill View Rare Plants”, Stephen Ryan’s “Dicksonia Rare Plants”, “Sanung Keban Collectable Plants” et al. In this category are Cyclamen creticum which we see in the gorges in Crete, along with Cretan dittany (Origanum dictamnus), the horned poppy (Glaucium flavum), the little bearded iris, Iris pumila, and deliciously aromatic Satureja thymbra, summer savory, which brings back memories of the Greek light.
One year we returned from Europe to a massive Ferula communis (giant fennel) in flower to welcome us home, having seen fields of it in Greece and Italy in preceding months. Another year we returned to the more subdued but very beautiful widow iris (Iris tuberosa,syn. Hermodactylus tuberosus) in flower. This was made more exciting by the fact that we had only seen its seed heads in Greece a few months earlier, though we usually see it there in full bloom.Plants in other people’s gardens also have their impact. We first admired the distinctive violet-blue cones on the Korean fir, Abies koreana, at Marwood Hill in North Devon – the inspirational garden created by the late Dr Jimmy Smart with plants from all over the world, including many from Australia. A pine up high, beneath the ornamental grapevine, began life as a bonsai many years ago (it has not been repotted since our previous garden and just manages to survive). From memory, it was a type of Pinus mugo. We like the contrast of needle-like leaves with the other foliages in our garden and find conifers are very undemanding. They grow slowly, tolerate the summer heat/winter wet and look good all year.
I had long yearned for an Abyssinian banana (Ensete ventricosum) with its huge leaves and bright red midrib. David’s verdict was always that it was far too large for our modest courtyard. A productive visit to the Adelaide Botanical Gardens “growing friends” in November 2004 revealed one of very modest dimensions, small enough to travel back to Melbourne with us on the aeroplane. Since being repotted it has quadrupled in size. A plant I admired on the same Adelaide trip was another tropical plant, the red-flowered Iochroma (I. coccineum) which Ruth Irving proudly pointed out at Al-Ru farm. A tiny form of this was available at the Ballarat Botanical Gardens’ “growing friends” nursery last January. It too appears to be flourishing in its new pot and environment.
Why do we have a pot garden?
A few tips
Terracotta containers filled with lemon trees are a common sight on Tuscan terraces in summer. The trees are trained to a handsome shape, giving a contrast of foliage and fruit colour to the garden. Lemons are one of the hardier citruses but even they can be damaged by a hard or prolonged frost and usually need to be moved under shelter to avoid the worst of the winter cold. Other citruses may also be grown in pots and I have found that the most successful of these are the kumquat family. These are small trees which can be pruned into neat and attractive shapes. The kumquat has an orange fruit which is good to eat and is about 3-4 cm long, the skin is soft and relatively sweet and the flesh acid. The abundant fruit remains on the tree throughout the year.
Kumquats are the hardiest of all citruses and require minimum winter protection. This characteristic has been bred into the limequat, which is a hybrid of the kumquat and the subtropical ‘Mexican’ lime. It has bright yellow fruit, slightly larger than the kumquat, with a pleasant acid lime flavour. It is one of the best citrus fruits for drinks and salads. I grow these in my garden as the fruit is seldom seen in markets or shops.
The members of the kumquat family flower in April/May and rapidly set numerous fruits amongst those of the previous year, so some are always available. The trees are neither bulky nor heavy and so can be easily moved, either out of the direct force of cold winter winds and/or into a shady position during the heat of summer. I find a pot of approximately 40 cm in diameter and 30 cm in height gives sufficient space for root growth. I use a mixture of commercial compost and sand with a layer of gravel on the surface to prevent excessive evaporation. A good soaking once or twice a week is adequate, with feeding every few weeks. A constant problem with pots in my garden is colonisation by ants. A simple remedy is to fill a terracotta dish with water and place the citrus pot in this on a second smaller dish which is inverted, thus keeping the bottom of the pot above the surface of the water. The ants are defeated by the moat.
I recommend these small attractive trees to those with either large or small Mediterranean gardens or even a small patio. The diced fruit are excellent in salads and sliced limequats taste and look superb in summer drinks.
What if you don’t have a garden?
When choosing containers, it is important to select those large enough for the crop you intend to grow. The greater the volume of the pot, the more likely the growing conditions of open ground can be matched. This is especially important with respect to maintaining water supplies. Tree and bush fruits need a depth of about 60cm and as much as 90cm in width, while annual vegetables or strawberries will manage with much less – though, as a rule of thumb, always provide a minimum depth of 15cm. A window box approximately 60cm long by 20cm wide can hold a useful selection of salad vegetables or herbs; a 40-45cm basket could hold strawberries or a trailing tomato plant. Make sure that pots for woody plants or for tall crops on climbing supports will not become top heavy when the crop is fully grown; they must be of suitably heavy construction, or use ballast to weight down lightweight containers. Vegetable containers should be sited away from full sun and wind exposure where they are likely to dry out quickly. Equally, avoid deep shade which will encourage legginess.
You can grow almost anything from apples and pears to cress in containers, though apples/pears are best raised on dwarfing rootstocks. The best choices are those that are compact, quick-growing and highly productive. Climbing peas, beans and courgettes grown on wigwams look lovely and crop well if fed and watered adequately. Fruiting vegetables such as tomatoes, aubergines and peppers are often sub-tropical or tropical in origin and, since they need sun and warmth for their fruits to ripen, are well suited to life on a sheltered mediterranean terrace or balcony. However, don’t go for vegetables which are deep-rooting, slow to mature, very tall or large, or really heavy feeders – such as brassicas, parsnips or celery.
Swiss chard (Beta vulgaris ssp. cicla var. flavescens) is perfect as a pot vegetable. It is a versatile crop with a long season whose bold foliage makes an attractive subject for the container garden and it combines well with annuals such as the red-wine petunias. Plants grow to about 45cm and have white stems that are wavy at the edges – they are regarded as something of a delicacy when cooked separately. Ruby chard is even more eye-catching with stems and ribs of scarlet and reddish purple leaves. Use the leaves as an alternative to spinach: they are a little less flavoursome but they are easier to grow and less susceptible to bolting. The plants take about 8-10 weeks to mature, so sow in early spring for early summer harvesting or in late summer for harvesting in winter and spring. Swiss chard is a useful cut-and-come-again crop: leave the heart leaves intact in the centres and the seedlings will resprout vigorously to yield another crop, ready to harvest again after about two weeks.
The bigger the container and the greater the volume of compost or soil, the better. Big feeders, such as tomatoes, generally need a container that measures at least 25cm deep and wide. Make sure your containers are well drained with several large drainage holes in the base, as waterlogging will lead to crop failure. Put plenty of broken crocks or gravel in the bottom to provide a drainage layer. Soil-based composts are best; they give more stability and are likely to hold on to moisture better. Adding up to 20 percent sand or grit will aid drainage and add weight. In addition it’s a good idea to add a compound fertiliser to the soil surface at a rate of 50 grammes per sq metre and work into a depth of 5-8cm.
There are two important things to know if you want to grow vegetables in containers: first, that they need a richer growing medium than usual as well as regular feeding, and secondly, that they need more consistent and thorough watering than vegetables grown in open ground. These points are critical. Nutrients are used up very quickly in free-standing containers; the roots have to obtain all their necessary nutrients from a smaller volume of soil than they would have done naturally so the soil needs to be enriched by regular feeding with a dry compound fertiliser or a liquid fertiliser. For longer-term performance, top dress container compost/soil in spring and change it completely every two or three years; after a while container media become compacted from frequent watering and less productive. The soil should be light and well aerated. Lighten with well-rotted compost mixed with coarse sand and peat or peat substitute.
The compost in containers dries out rapidly in hot weather, and you must be prepared to water container-grown vegetables twice a day. To help conserve moisture, keep the upper surface mulched with 5cm of organic material (compost, cocoa-bean shells) or pebbles. Be aware that in hot and windy weather containers dry out really quickly, both through evaporation from the top and also through the sides – especially with terracotta pots. To minimise losses, make sure your pot is not in an exposed situation or at the foot of a hot wall. If you use a terracotta pot, line the sides with thin plastic sheeting which will effectively reduce water loss. Surface evaporation can be reduced by applying a mulch of well-rotted organic matter. Give close attention to watering – watch the plants and weather conditions. You need to keep the top 20cm of soil moist. Lack of water, even for a brief period, can lead to slow growth, peppery flavours and bolting in all crops. With vegetables you can never assume that natural rainfall has done the job for you. Take heed of these two points and you will be able to grow an interesting selection of fruit and vegetables in a restricted space.