This month the brief was to write about a ‘Caudiciform Plant’.
The general definition of a caudiciform plant is one that has a swollen underground root system that is able to store moisture. We will normally grow these plants with the large storage root partially above ground.
Many succulent species can be described as caudiciform, such a wide description gives me the chance to discuss a plant from one of my favourite genera and also from my favourite habitat.
E.primulifolia is quite widespread in southern Madagascar but does exhibit some variation in size and leaf formation as the species progresses southwards.
A large concentration can be found south of Fianrantsoa, thousands of plants cover three hillsides and all the plants at this location have the tuberous roots completely below ground with only the rosette of leaves visible on the soil surface. Plants in these hills are growing in a very open ash like material and there is a large variation in size. The plant shown is in my own collection, 12 cm diameter, and is typical of the form in this locality.
Further south in the Ishalo Mountains is another location where the plants again are completely buried with just the rosettes showing. They are growing in what appears at first sight to be a quartzitic substrate but just below this fine layer of quartz is very silty, sandy soil. The tubers on these plants again are very large.
Further south again is another form much smaller but growing in very sandy gravel.
Cultivation of these plants, in my opinion, requires a very free draining soil mix. For all my Madagascan Euphorbias I now use a combination of akadama, pumice and other volcanic materials. A winter temperature of at least 10 degrees Centigrade is essential – higher if possible.
Leaf drop in the winter dormant period is normal, they should then be kept fairly dry. In the spring leaf rosettes will appear and a fair amount of water can then be given providing the compost is free draining. I usually dunk my whole pot in water plus added fertiliser and repeat the process when it dries out.
Small ‘flowers’ will appear in early spring to late summer and are usually white but can have a pink tinge.