About the genus
Pachypodium was first published as a unique genus in 1830 by John Lindley. Pachypodium, along with the genus Adenium, is a member of the Apocynaceae. The species include a group of succulent bottle or candelabrum-shaped, spine-bearing, tree-like plants and dwarf shrubs with a short trunk. The spines would be considered as modified stipules.
The different plant shapes and the five-fold symmetrical flowers of white, yellow or pink make this an interesting group of plants to grow. The current literature suggests there are 25 species, and all plants are native to Southern Africa and the western areas of Madagascar.
Madagascar has the most species, including recently described species such as P. inopinatum in 1996 and P. mikea in 2005.
The plants grow from sea level to around 1,900m in a range of sand, limestone, gneiss and quartz rocks. Most species of Pachypodium have an extremely limited distribution range and are at risk from new industries or changes to their habitat.
How to grow them
Growing these plants from cuttings has been largely unsuccessful and therefore growing from seed is the best option. Seeds can be surface sown from March onwards and one method is outlined below.
The recommended mix is a general-purpose compost with a small aggregate to make up at least 50% of the volume. Air and good drainage, as for most succulents, are essential for success. A John Innes mix is considered too heavy hence the lighter material being suggested here.
Seed can be bought from suppliers but not all species are available commercially. Seed is often supplied in packets of 10 and these can be divided so there are two to three seeds per 5cm pot.
Place the pots with compost in a tray and bottom-water and, once the compost is wet, remove the pots. If you wish to sterilise the soil this can be done using a microwave, then the pots are placed in individual sealed polythene bags. When the compost has cooled, place seeds on to the compost surface, but do not handle the seeds, seal the bag and keep warm around 20°C.
Germination occurs within a week or so but not all seeds germinate. The different species vary in growth rates, for example Pachypodium lamerei and P. geayi grow relatively quickly whereas P. brevicaule is much slower. Under the conditions above plants will establish quickly and the bags can be removed shortly afterwards.
Seedlings require space so pot on with one plant per pot. Pachypodium in general require good light and should be kept dry over winter with a minimum temperature above 10°C. Watering can start when light intensity and temperatures increase in the spring, with a regular half-strength low- nitrogen feed. A potting mix as used for seed sowing is also suitable for more mature plants.
Text and photos: David Bruno
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