The genus Aloe, according to current reckoning, extends to about 500 species. It is easy to see them along the roadside and in many Riviera gardens but it is difficult to find a really big collection of them, even though the genus is popular with plantsmen. Some years ago, there used to be a beautiful collection in the garden of an hotel at Ospedaletti, but unfortunately the owner died, leaving his beloved plants uncared-for, so that slowly the collection went back until I got involved with it – by which time many of the specimens had died.
Madagascar has the greatest number of short-growing species, which are the best for plantsmen’s gardens. We will come back to them later, but meanwhile it is worth noting that some of the very large species also lend themselves well to open-air cultivation, so long as the temperature does not dip below zero for too long.
Monaco’s Jardin Exotique has many aloes that live happily in the open, though it is not easy to find similar positions to plant them; nevertheless there are many places along the coast where the sea’s influence keeps the temperatures above freezing and it is safe to embark on the cultivation of aloes.
Many aloe species are in danger of become extinct in the wild because of deforestation, fire, drought and uncontrolled or excessive collection. Often they exist only in very small areas, no more than a few hundred metres square, and for these the risk of extinction is even greater. Aloe silicola, A. oligophylla, Aloe edouardii and many others no longer exist in the wild but have fortunately survived in collections made by botanists and amateur plantsmen. The only known site of A.
bakeri, near Fort-Dauphin, was destroyed, together with a whole hillside, when it was quarried to provide stone to build a port. Even the beautiful, climbing species A.
peyrierasii is robbed of its leaves by Madagascans to make a tisane – it is regularly sold in markets – until the plant can take it no longer, and dies.
Comparatively few species are available from the nursery trade because they need to be easy to cultivate and grow well indoors. The beautiful Aloe variegata is widely grown and easy to find in garden centres and florists. Its leaves are 10-15 cms long, with white stripes. It comes from South Africa and is propagated from seed. A.
erinacea from Namibia has black spines that are white on the young plants. A. vera, also known as A. barbadensis, has been cultivated for centuries for its medicinal properties and is now naturalised in many warm climates. A. rauhii is a species that is actually listed in CITES Appendix 1, among the most vulnerable to extinction in the wild, but is so easily propagated that its survival is assured. The tiny Madagascan A. parvula is also highly protected but of easy cultivation. A. vaombe, by contrast, is a majestic tree with large red flowers, though there is also a rare form with yellow flowers. Its Malagasy name translates as ‘big aloe’ and, together with the zebu ox, it is the true emblem of southern Madagascar. It will tolerate near-zero
temperatures, provided they do not last too long. A. dichotoma is another species that can reach 10 metres in height, branching as it grows. Although it comes from South Africa and is therefore more vulnerable, in theory, to low temperatures, I have found that my own specimen, which is about 2 metres high and grows in a bed in front of my house, puts up very well with the frost and snow of a bad winter.
My advice to people who want to grow aloes outside is to prepare the soil so that is extremely free-draining or, even better, to plant them on rocky slopes where there is absolutely no danger of standing water. Aloes show their best colours only if they are grown without too much watering. Otherwise they concentrate on growing. In fact, the best way to bring on their flowers is not to lay off watering them for a while and treat them to a period of dryness.
Like all succulents, aloes may be affected by root-rot if they are allowed to stand in water, especially when they are pot-grown. Young plants, in particular, are sometimes attacked by cochineal beetles. It is best to give them a preventative treatment twice a year, though their natural defence systems are much stronger when aloes are planted out in the garden. And some species are vulnerable to red spider, which one tends not to notice until quite a lot of damage has already been done.
In my experience, it is best not to give them a lot of fertiliser. Choose low-nitrogens feeds, because nitrogen softens up a plant and makes it more susceptible to fungal diseases and sap-sucking insects.
In conclusion, I would emphasise that aloes can be grown fairly easily provided you choose the right species for your climate. In colder areas you will need to set up a small greenhouse with a heating system to protect them. For those in kinder climates, all that is needed is basic protection during the colder months and here I would particularly recommend using a horticultural fleece that protects them without locking in the humidity.
Bibliography: Les Aloes de Madagascar – Jean- Bernard Castillon & Jean- Philippe Castillon