Container gardening – what plants to grow and how to care for them

The photograph at the top of this page shows elegant flower pots at Palacio de Viana, Cordoba (Photo Alisdair Aird)

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 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.

Growing Plants in Pots
by Caroline Harbouri

Some Salvias Grown in Pots
by Caroline Harbouri, extracted from TMG No. 63 January 2011

Notes on growing cacti and succulents in containers
by Stavros Apostolou, translated from the Greek Cactus Forum

Small Aloes for Pot Gardens
by Trevor Nottle reprinted from TMG No. 56 April 2009

Gardening in Pots in Melbourne
by Caroline Davies, extracted from TMG No. 43 January 2006

Wildlife Gardening for Balconies and Gardens
report of a lecture by Martinos Gaethlich from News & Views

For additional reports and articles on this subject please check out the (non-responsive) MGS Archive.

Growing Plants in pots – a talk to members of the Greek Branch
by Caroline Harbouri

Pots

• Terracotta versus plastic pots: terracotta pots look nicer and ‘breathe’, but plastic pots are much lighter when weight is a consideration on balconies and roof terraces. By ‘breathing’ I mean that terracotta pots, being porous, lose moisture by evaporation from their sides, making the soil within them less likely to become dank and stagnant. Plants in plastic pots will need slightly less water than those in clay pots and care must be taken not to over-water them.
• To help achieve good drainage, it is usual to place bits of broken flower-pot or pebbles at the bottom of the pot before adding soil and planting. Although I always do this with terracotta pots, I have found when I re-pot plants from plastic pots that the potsherds or pebbles invariably have been drawn up into the root ball, often by several inches. I don’t know why this happens, but as a result I have stopped using this drainage material in plastic pots. Instead I pierce more drainage holes in the bottom of the pots than those provided. Good drainage may also be assured by raising the pots on two bricks, or of course by using the pot stands available commercially.
• If you have saucers under your pots, remove them in autumn/winter so that the plant doesn’t sit around in water after rain.
• Always choose the size of the pot to fit the plant, in other words don’t put small plants in large pots. The reason for this is that as the plant’s roots take up water, oxygen is drawn into the soil. If the pot is too big, there is a large volume of soil from which water is not taken by the roots and which thus remains deprived of oxygen and stagnant or even waterlogged, causing the plant to do badly or die.
• Avoid pots with rounded sides, i.e. narrower at the bottom, swelling out in the middle then narrower again at the top: when the time comes for re-potting your plant, it will prove impossible to get it out of a rounded pot without breaking the pot.

Soil

• Acid-loving plants like gardenias and camellias need special, more acidic, soil (in Greece this is the kind called kastanóhoma).
• For most other plants any good general-purpose soil is suitable. Bear in mind that commercial potting composts with a lot of peat in them don’t absorb water well if they have dried out completely. Peat is in any case an unsustainable product and should thus be avoided.
• If your pots are on a balcony or roof terrace avoid using terra rossa (the red clayish soil) since it is particularly heavy.

Watering 

• How much water your pots will need and how often they will need watering depends on the type and size of plant, their exposure (full sun, partial shade, shade) and the weather conditions (temperature, wind).
• More plants die from over-watering than from under-watering.
• If you install drip irrigation, choose the output from each dripper according to the plant’s needs (e.g. pelargoniums need smaller quantities, annual climbers need more, etc).
• Watering by hand has the advantage that you can assess each plant’s needs individually, day by day.
• Whether by drip irrigation or by hand, always water early in the morning or in the evening.
• Avoid spraying the foliage of oleanders with water in summer as this tends to cause galls on their stems and branches.

Pruning

• You can cut back almost all shrubby plants for a better shape or to reduce their height (but – if you grow them – avoid cutting into the old wood of lavenders and rosemary, which tends to cause die-back).
• You can also cut back hard any plants that are damaged by frost, but it’s best in this case to wait until you can see the extent of the damage when the plant re-sprouts in spring.

Root pruning

• If you have a shrub that has been for many years in a large pot and you don’t have the space to re-pot it into an even larger pot, you can remove the bottom third of its roots, e.g. by simply sawing through them, and then put the plant back into its original pot with some fresh soil at the bottom. In this case, to help the plant recover, remove at the same time at least a third, or even more, of its top-growth. You can repeat this treatment every two or three years.

Microclimate

• In hot sunny conditions plants do best when their pots are placed close together since each plant provides some shade and atmospheric moisture to its neighbour. 
• If possible move the pots further apart in winter to allow air to circulate between them.

Fertiliser

• The regular watering of pots leaches nutrients out of the soil, and of course the plant itself exhausts them. A dose of a balanced fertiliser (there are many on the market) given every ten days or so during the growing period from late spring to early autumn promotes good growth and flowering. Follow the product’s instructions as to dilution carefully.
• If a plant shows signs of chlorosis (yellowing leaves), give iron: water-soluble iron for plants is available at all garden centres. But check first that the leaf-yellowing is not due to over-watering.

Pests

• Aphids (including greenfly, whitefly and the fat orange aphids found e.g. on oleanders): the problem will usually disappear as the summer advances. In bad cases, cut off and destroy affected shoots and/or spray with a soap or washing-up liquid solution to which a few drops of pharmaceutical alcohol are added.
• Ants ‘farm’ aphids for their sticky honeydew. Apart from this ants aren’t generally a nuisance to plants in pots. However, if they have made a nest in the soil of a pot (a tell-tale sign is little piles of finely-sifted soil around its base) they tend to disturb the plant’s roots, thus re-pot it, getting rid of the white ant eggs and ants. There are proprietary poisons for ants but since I don’t use them I can’t advise on them.
• Scale insects, both the kind with a hard shell and the soft white squishy ones: pick them off by hand and destroy. Where woody stems are affected, wipe the stem with cotton wool soaked in alcohol. This treatment does not solve the problem completely but keeps it under control. Remember to check the undersides of leaves.
• Slugs and snails: collect them when you see them and dispose of them in any manner you’re not squeamish about. Don’t use anti-snail or slug pellets if you have dogs or cats as they can be lethal to them. Crushed eggshells or coffee grounds placed on the soil around plants to some extent deter snails. Vaseline smeared round the rim of the pot is also said to deter them – but beware, it is all too easy to break pots when you pick them up forgetting that they have slippery Vaseline on them… Remember that slugs and snails congregate under the turned-down rims of plastic flower-pots.
• Check plants for aphids and scale insect before you buy them.

Hygiene

• The down-turned rims of plastic pots can also harbour eggs of scale insects and other pests. Wipe under the rim with cotton wool soaked in alcohol at the beginning of spring and perhaps once again during the course of the summer.
• Sterilise pots that you are going to re-use with boiling water, including under the rims.
• Sterilise your secateurs and saw every so often to avoid spreading pests, either with boiling water (in which case dry carefully at once) or by wiping them with alcohol.

Good shrubs for pots in sunny positions:

• Oleanders
• Lantanas (both the shrubby Lantana camara and the creeping Lantana montevidensis)
• Brugmansias (commonly sold as daturas: properly speaking, brugmansias have pendent trumpets and daturas up-turned ones) – wonderfully scented in the evening
• Cestrum nocturnum (lady of the night) – powerfully scented on summer nights
• Jasmine, Jasminum officinale and Jasminum polyanthum. The former flowers throughout the summer, but the latter flowers only once in spring
• Plumbago (sometimes burnt to the soil level by frost but usually comes back in spring)
• Pelargoniums – which include the pot plants we usually call geraniums: I’ve found the ivy-leaved trailing ones withstand very hot sun best.
• Hibiscuses (Hibiscus rosa-sinensis), red or other colours, but don’t forget that they are tender and need protection from frost
• Callistemon citrinus, the Australian bottlebrush
• Asclepias curassavica (orange and red flowers)
• Rue (Ruta graveolens): swallowtail butterflies breed on this plant and their caterpillars may strip it bare, but in my experience the plant usually recovers and puts out fresh leaves.

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:

• Campsis radicans and Campsis grandiflora (orangey-red and orange trumpets respectively, the former narrower; there is also an apricot-yellow form, C. radicans f. flava)
• Tecoma capensis (narrow trumpets in orangey-red; also clear yellow and apricot-coloured cultivars)
• Solanum jasminoides (clusters of pale mauve flowers)
• Podranea ricasoliana (pink trumpets)
• Pandorea jasminoides (white or pale pink trumpets with dark crimson throats)
• Bougainvilleas, bearing in mind that the classic magenta-coloured one is most resistant to frost.
• Passion flowers – the common Passiflora caerulea or other species

Don’t forget annual climbers, easy to grow from seed. The following can usually be found in garden centres:

• Morning Glories of various kinds (Ipomoea species and cultivars including the lovely Ipomoea tricolor ‘Heavenly Blue’)
• Cobaea scandens (the bell-shaped flowers open pale green in the morning and then turn mauve by evening)
• Thunbergia alata (yellow or orangey-yellow with black centres: what in England – though not America – is called Black-Eyed Susan).

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…

Some Salvias Grown in Pots
by Caroline Harbouri

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.
Before I note them one by one, I should describe briefly the manner in which my plants are grown. All the plants on the roof terrace are in plastic pots (I do hate plastic pots and would much prefer terracotta but, given that I have a great many plants, I had to take into account the very substantial difference in weight between plastic and terracotta, grit my teeth and go for plastic). I use a fairly light leaf mould-based potting compost – the terra rossa of Attica is too heavy for a roof. All plants are watered every day in the height of summer by drip irrigation or by hand, and are hand-watered according to need during the rest of the year. All are exposed to full sun from morning to evening in summer, without any shade except that which neighbouring plants provide for one another. Since for reasons of space as well as weight I cannot go on repotting infinitely into larger pots, all large shrubs that can’t be divided are submitted to a brutal regime every couple of years: I pull them out of their pots, chop off the lower third of their roots, prune the top growth by about a half to two-thirds, then replace them in the same pots with fresh soil. All have responded well to this treatment so far. Other plants are divided when they outgrow their pots – which produces plenty of material to give to friends.
None of my salvias has yet undergone this drastic treatment, though one or two have been divided. I list them in no particular order.

Salvia coerulea (syn. S. guaranitica)
This is the exception, in that I grow it not on my roof but in my diminutive courtyard at ground level, which means that it is in a terracotta pot. It came to me as a rooted cutting from Sparoza and is now taller than me. I very much like its large rich dark purple flowers with dramatic near-black calyces growing through the foliage and pink trumpets of a neighbouring Podranea ricasoliana. It grows so profusely that I’ve been cutting it back quite regularly. I plan to repot it this winter. This summer it has been afflicted by scale insect (the only one of the salvias I grow to suffer from any pest), which I have treated by personal attention: I remove the horrid creatures by hand and wipe the affected stems with cotton wool soaked in a soap solution to which a few drops of pharmaceutical alcohol have been added. This seems to work up to a point.

Salvia × jamensis
This is a huge success. Even in a pot it grows into a large and rambling, slightly messy, shrub with scented green leaves and produces its clear crimson flowers (rather like those of S. microphylla but slightly larger) for months and months throughout the year, although its main flowering is in early summer. I cut it back whenever it seems to be getting too enormous and it rewards me by growing more lustily than ever. I wouldn’t be without it.

Salvia elegans
The pineapple sage – though I can’t say it smells very strongly of pineapple to me. Of all my sages, S. elegans is the least happy on my sun-baked terrace in summer; considering that it comes from the highlands of Mexico, this is hardly surprising. I thus take care to tuck it well under the shade of larger plants in July and August, and make sure that it has a saucer beneath its pot to keep it damp. Once the heat of the summer is over I bring it forward again and it comes to life: as I write in November, it is covered in spikes of vermilion flowers.

Salvia madrensis
This is a yellow-flowered salvia which also came to me from Sparoza. In truth, I am not particularly fond of its spikes of flowers, produced in autumn, for they always look somehow anaemic to me (though I don’t go as far as to cut them off when they appear). I grow it mainly for its beautiful, large dark green leaves which have a wonderful crinkled texture and make a good contrast with the foliage of other plants around it. The square stems characteristic of salvias are very apparent, with pronounced joints. It’s a thirsty plant which rapidly spreads to fill its pot and has to be divided. I cut it back to soil level every winter. Its new growth in spring seems to be particularly attractive to snails, so that regular night patrols with a torch are indicated.

Salvia leucantha
This too is cut back to soil level every winter, but luckily snails don’t seem to be very interested in it. I have a great liking for the velvety, chenille-like texture of its flowers. Mine, flowering now in November, is a good strong purple and white; I find the paler-coloured ones less attractive. A pink-flowered cultivar, seen last year in Cyprus, was a curiosity that didn’t tempt me. I used to grow this plant in my garden but find it does equally well in a pot. In fact I suspect that, unless fairly well watered in the garden, it may actually look better growing densely and lushly in a pot – in Monterey I saw it in many gardens but noted that it always seemed a bit straggly and meagre-looking.

Salvia officinalis subsp. lavandulifolia
Generally speaking, the classic aromatic Mediterranean plants, like rosemary and lavender don’t do well or last long in pots, for they are adapted to dry conditions and thus like to send their woody roots down deep into the ground. They also don’t like the regular watering which pot cultivation makes necessary. I’ve thus never attempted to grow either Salvia officinalis or S. triloba in a pot. However, this mauve-flowered aromatic sage is a slightly less woody plant and I’ve had it in a pot for the last five years without mishap. Its flowering season in spring is fairly short, but for the rest of the year, cut back a little, it makes a neat, quiet, grey-green mound that always looks good.

Salvia uliginosa
I’ve never grown this salvia in the ground – in a pot it likes a lot of water (to be expected, since it is commonly called the Bog Sage). It is worth every drop, however, for its tall spikes of sky-blue and white flowers, much loved by bees, and its fresh green, rather mint-like, leaves.

Salvia farinacea
I grow side by side both S. farinacea ‘Victoria’, with purple flowers, and a (name unknown) white-flowered cultivar. Both are cut down to soil level in winter. Both make unassumingly pretty pot plants, reasonably bushy with soft foliage, not much more than 18 inches tall and fairly free-flowering. To my eye there is nothing very farinaceous about ‘Victoria’ but the white-flowered plant has a floury look which makes me immediately understand its common name of Mealy Sage.

Salvia discolor
I’ve left this one till last for it is my favourite. It is a wonderfully handsome plant, the very prince of salvias, with pale undersides to its matt green leaves, white stems and fine black flowers in pale jade-green calyces. It is somewhat tender, so that a couple of years ago Sally Razelou gave me her (then) only precious S. discolor in a pot for me to over-winter for her, feeling that central Athens would be warmer than Sparoza. This was a terrible responsibility: I anxiously checked it daily, frightened lest I let it die and had to face Sally’s wrath. I’m glad to say that it didn’t die; indeed it subsequently provided the cutting from which my own plant came. I brought my S. discolor down from my roof terrace last year to over-winter it in the more sheltered conditions of the courtyard. It suffered from the damp, however, and began to look more than a bit miserable, though rapidly recovering as soon as I moved it back up on to the terrace in spring. This winter I shall have to find it a place that is protected from the wet as well as from the cold. If I could grow only one salvia, then this would be it.

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. I can see that this winter I am going to have to do some detective work to try to put names to them.

A Gallery of varieties and cultivars of Salvia, many of which would be suited to growing in pots, can be found here.

Notes on growing cacti and succulents in containers

by Stavros Apostolou, translated from the Greek Cactus Forum

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.

Whether the amount of water is excessive depends not only on how much the plant is watered but also on how much water the soil in the pot holds. The aim is to allow the plant to dry out quickly. A couple of days in moist soil is enough for the plant to get what it needs for its development. Newly-bought cacti and succulents that are grown in peat mixes, which include most commercial potting composts, should be repotted at the earliest opportunity into a soil mix with good drainage because the peat holds water and makes plants more susceptible to rotting and disease. The best course of action is to make your own mix which you know will not hold water and moisture for longer than two days. (See below)

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.

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.
With Lithops, in my opinion it is always preferable to spray rather than water.

Rules of watering cacti and succulents:

• Between waterings the soil should dry out completely.
• If the plant is watered too much it is likely to crack or rot which is irreversible, whereas if the plant is under-watered it may get a little dehydrated but this will be corrected with the next watering.
• Better under-watered than rotten.

Repotting container-grown cacti and succulents
When repotting cacti and succulents remove the plant carefully from the old pot and check the state of the roots. If they are healthy and there is no sign of any infestation of insects, plant again in a slightly larger pot without disturbing the existing soil. If all is not well then carefully remove all the soil from the roots, cut off all dead and rotting roots and, if necessary, spray with an insecticide and leave to dry for a day or two. Plant up with fresh soil but do not water. In contrast to all other plants, cacti and succulents must be left dry for six to eight days after being transplanted to avoid the danger of root rot. Any roots which have been damaged during the transplanting operation need time to heal before they are doused in water.
Rules for repotting cacti and succulents:

• Use the opportunity to correct root damage and insect infestation.
• Do not water for 6-8 days.

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 example, cacti and succulents with tuberous roots, e.g. Ariocarpus, Leuchtenbergia, some Mammillaria, Pterocactus etc., should be given a soil mixture with particularly excellent drainage, hence without extra peat moss or leaf mould, but anything sharp like stones and shells which are sometimes used to open the soil mix for better drainage should be avoided of fear of damaging the tuberous roots. An injured root is prone to rot after watering. A mix for these plants may contain ready-made cactus soil, perlite, lava (fine), fine sand and generally materials that do not have sharp edges.

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.

In their natural habitat, plants in the genus Copiapoa have adjusted to getting the water they need from mist and the morning dew. When grown in pots they can be watered normally but with care in a mix of ready-made cactus soil supplemented with perlite, sand and pumice or lava. The best medium for Copiapoa cinerea and generally for grey-coloured cacti is gravel.

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.

For succulents that need a richer soil such as Gasteria, Haworthia, some Agave and Aloe, the mixture may be made from ready-made cactus soil mixed with leaf mould (cleaned of the larger pieces of leaf and wood if necessary) and a little perlite.

A similar mix can be used for Lithops, Conophytum and Pleiospilos but with sand as well as perlite.

Tropical cacti such as Hatiora, Lepismium, Pfeiffera, Schlumbergera and Rhipsalis can be planted in the basic mix of ready-made cactus soil, perlite and sand or the cactus soil can be replaced totally or in part by pine bark.

Soil rules

• Most commercially grown cacti and succulents are potted in peat and should be repotted immediately.
• The soil mixture has to be very well draining and to dry out within one or two days.

All photographs in this section by Stavros Apostolou.

Small Aloes for a Pot Garden
by Trevor Nottle reprinted from TMG No. 56 April 2009

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.

A Gallery of Aloes many of which would be suited to growing in pots, can be found here.

Gardening in Pots in Melbourne
by Caroline Davies, extracted from TMG No. 43 January 2006

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?
Most people’s reaction to pot culture is that it must be much harder work and more difficult to water than a conventional garden. We grow plants in pots because we believe the opposite. The secret is a little work every day, with a vigilant eye for pests and diseases (David does a “slug patrol” with a torch most nights), regular dead-heading, pruning, removal of dead leaves, feeding and watering.

I use an attachment to our hose (a wand with a spray-head) which concentrates water on a particular plant, like a shower, saves considerable time and means that there is no waste. It is important to water each pot thoroughly and always to water before a 40-degree day, not a rescue mission afterwards. All plants have different needs and the succulents do not need the regular soak of the ginger lilies, ferns and pot-bound shrubs. I alter watering technique from one to another. The exception is dormant plants which are placed on shelves behind the scenes or on the balconies.

The entire garden takes me less than twenty minutes to water thoroughly. On busy days this job can be done at night (with our outdoor lighting) – a pleasant chore in very hot weather.

Many delicate plants I used to lose in my previous garden do very well in pots. They can be moved to the shade in summer or to the sunny front garden in winter. They are never dug up by mistake or overwhelmed by a stronger plant and its roots.

Plants that are difficult in our climatic/soil conditions can be nurtured in pots and flourish, e.g. auriculas and snowdrops (Galanthus) – a true indulgence, especially as the neighbourhood sparrows can be a real pest and nip off the flower-heads of the latter.

When plants have their quiet period they can be hidden away. Others in flower can be moved to a prominent position. Finally plants in pots are contained: they can never take over the whole garden, turning it into a jungle when we are away…

A few tips

• All plants need good drainage. We place a layer of gravel/grit in the bottom of the pot before we fill it with potting mix. If you have no time to make your own, it is well worth using the best (and most expensive) potting mix. An “ultra premium potting mix” has a number of additives including water-storing crystals, controlled-release fertiliser, etc. Container plants only have access to the nutrients supplied in the mix and in subsequent feeding programmes, so if the mix is poor this will be reflected in the plant’s appearance.
• One advantage of container plants is that potting mixes can be varied according to plants’ individual needs. As an experiment with our grass tree (Xanthorrhoea sp.) we have used a mixture of half Australian plants’ potting mix and half garden loam – to give substance and body – as normal potting mixes break down more quickly. We use a special orchid-growing medium for our orchids (mainly dendrobiums) and our bromeliads – which need an open mixture that drains rapidly.
• We add a layer of gravel or pebbles on top of many of our pots. This looks more attractive than an expanse of soil in a large container. It acts as a mulch and also prevents the plant from becoming waterlogged or rotting. It also deters the blackbirds who can create havoc with my bulbs, cyclamens and delicate emerging shoots as they excavate for worms. The pebbles also stop the soil from being swept to the ground during watering.
• I feed regularly during the growing season and am a great advocate of liquid seaweed plant food. In Melbourne, I use Maxicrop or Seasol, not only as a food but as a tonic when plants are not doing too well. I also use it when potting up a new plant or repotting, to help develop a healthy root system. Liquid seaweed also appears to build up a plant’s resistance to excessive heat in summer and cold in winter – both common features in our city. With certain plants, I supplement this with Phostrogen, containing potash to promote flowering.
• I try to find the time to repot all my special bulbs and cyclamen every year. Other plants are repotted when they really have outgrown their existing container. Sometimes (to inhibit growth) we trim the roots back with sharp secateurs and put the plant (also pruned) back into the same container with fresh soil and a dose of seaweed tonic. When a repotting task is daunting, we remove the top few inches of soil, replace with fresh potting mix, and wait another year. We picked up this idea in Italy, where the lemon trees in a Lucca garden we know well have not been repotted for well over twenty years.

THE MEDITERRANEAN GARDEN is the registered trademark of The Mediterranean Garden Society in the European Union, Australia, and the United States of America

Data Protection Consent

website designed and maintained
by Hereford Web Design