Events

Flowers from The Cape

Derek Tribble (author and lecturer)

Succulent Plants

South Africa is the richest place on Earth for succulent plants. Of approximately 10,000 species of succulents world-wide, over 40% occur in southern Africa and they contribute nearly 20% of the native flora. However, they are not evenly spread; there are wonderful places where nearly all plants are succulent. Succulent plants have adapted to life in areas with seasonal rainfall, by developing water storage tissues within some part of the plant. This is usually either the stem as in euphorbias and stapeliads, or the leaves as in crassulas, aloes and mesembryanthemums. Those parts of the plant have become thickened and the epidermis around them has become resistant to water loss.

Cultivation of Succulent Plants

Temperature & situation

In general, very few water-storing succulents can tolerate freezing. Usually reliable outdoors in south-east England are Aloe aristata, Carpobrotus acinaciformis, Crassula sarcocaulis, Delosperma nubigena and Ruschia uncinata. Therefore most succulents are grown as pot plants. Some of the most neglect-tolerant windowsill plants are succulents, but a heated greenhouse provides the best accommodation. However, most South African succulents do not like continual high temperatures; cold nights below 10°C (50°F) are needed for their metabolism to function well, particularly those that are actively growing during the winter. Night-time temperatures of 3°C are acceptable for many species.

High light levels are important for these rewarding plants, since they do not possess large leaves. A sunny windowsill or top-staging position in a greenhouse is essential. A few genera can tolerate shade e.g. Haworthia, Gasteria or Stapelia, but even these look better in sun where interesting colourations can develop.

Potting

Reflecting their semi-arid habitats with poor rocky soils, extra drainage material (e.g. grit) must be added to commercial potting mediums - add at least a quarter by volume. Shallow plastic pots are usually used, but porous clay pots enable succulents from arid places to dry out more quickly in the winter. Feed with weak-strength, low-nitrogen fertiliser, particularly if the plant has not been re-potted recently and nutrient leaching is suspected. Top dressing with grit does look attractive, but beware that it inhibits evaporation and hides any potentially disastrous water-logging of the soil.

Watering

Rainwater is needed in areas with hard (alkaline) tap water. Always water succulents thoroughly. Allow them to dry out briefly between waterings and never keep the pot standing in water. The commonest succulents in cultivation, such as many aloes, crassulas and haworthias, tend to originate from southern South Africa, an area of all-year rainfall. Consequently, water these throughout the year, but less frequently in winter. The eastern side of South Africa experiences summer rainfall and these succulents, such as most stem-succulent euphorbias and stapeliads, need a long, dry winter rest for several months (as for cacti). In contrast, leaf-succulents such as crassulas, mesembryanthemums and othonnas predominate in the Mediterranean climate of the western side of the country. These need little water during their summer rest, but come into growth at the autumn equinox as the days shorten and night temperatures drop. However, in the UK, do greatly reduce watering during the coldest couple of months, but start again as early as possible in spring to enable a second growth phase before the summer shut-down.

Hygiene

At a warm time of year, spray succulents occasionally to wash dust away, unless the plant is farinose. Prune shrubby or leggy species into a symmetrical shape. Always remove dead, dried-up leaves and flowers before the start of gloomy UK winters to avoid fungal problems. The main pests to watch-out for are mealy bugs which wrap themselves in woolly cocoons and the minute red spider mite which causes light brown discoloration of leaves and growing points. Be aware that some pesticide drenches can damage leaves that have waxy coatings.

Online Succulent Information

Cactus and Succulent Plant Mall (http://www.cactus-mall.com/): An indispensable portal gateway for cactus and other succulent resources, containing information about societies, public collections, suppliers of plants, seeds, literature and more. Many UK nurseries listed on page www.cactus-mall.com/nursery/nlistuk.html

Succulent Plant Page (http://www.succulent-plant.com/): General information about cacti and other succulents including cultural advice.

Adromischus Displayed (http://www.dvtribble.demon.co.uk/): Symposium presenter’s web site for the genus Adromischus (Crassulaceae).

Reference Books

Illustrated Handbook of Succulent Plants (www.springer.de/succulent_plants/). Editors: U. Eggli & H. Hartmann, in co-operation with the International Organisation for Succulent Plant Study (2001-2003); five vols, starting ISBN: 3-540-41692-7. Comprehensive treatment of over 9000 taxa of all possible succulent plants, except cacti; can be consulted in the Lindley Library.

Succulents of South Africa, a Guide to the Regional Diversity, E van Jaarsveld, B-E. van Wyk, & G. Smith (2000), ISBN: 0624038386. Describes succulents in 16 regions; excellent value overview.

Succulent Plant Societies

British Cactus and Succulent Society (http://www.bcss.org.uk/): Main UK society with quarterly journal, seed list, c. 100 branches, national shows & conventions. Membership Secretary: Mr D V Slade, 15 Brentwood Crescent, Hull Road, York YO10 5HU.

Succulent Society of South Africa (http://www.succulents.net/): Quarterly journal Aloe, seed list, conventions (Succulenta 2003 is in Calitzdorp). Contact address: Succulent Society of South Africa, Private Bag X10, 0028 Hatfield, Pretoria, South Africa.

Haworthia Society (www.cactus-mall.com/Haworthia-Society): Interests include Aloe, Bulbine, Gasteria and Haworthia. Four-monthly journal, Haworthiad, plus seed lists and biennial convention/show. Treasurer: Mr S Baker, 7 Whitney Avenue, Redbridge, Ilford, Essex IG4 5PN.

International Asclepiad Society (www.cactus-mall.com/ias): Interests include Ceropegia, Pachypodium, stapeliads, etc. Four-monthly journal, Asklepios, and seed list. Membership Secretary: Mr L B Delderfield, 2 Keymer Court, Burgess Hill, West Sussex RH15 0AA.

Mesemb Study Group (http://www.mesemb.org/) for all members of the Mesembryanthemum family, e.g. Conophytum, Delosperma, Lampranthus and Lithops. Quarterly bulletin, excellent seed list, occasional shows & meetings. Editor: Mrs S Mace, Brenfield House, Bolney Road, Ansty, West Sussex RH17 5AW.