Thick Foot

My interest in collecting succulents has for the longest time been focused on the rarer Mexican and South American cactus genera, the Haworthias and Gasterias endemic to South Africa, and some of the rare Euphorbias and Stapeliads from Somalia, Ethiopia, and the surrounding regions. A few years ago, my friend Peter Bangayan got me interested in another area of succulents called the caudiciforms. These are succulents which produce a fat stem or caudex as their means of coping with their stressful environments and as a means for storing water for the plant’s survival. One of the most popular genera of caudiciforms are the Pachypodiums. Peter has a wide and extensive collection of caudiciforms. Many of his wards are grown from seed, which takes quite a bit of patience, but with plants like Pachypodiums, these grow a lot more quickly from seed than cacti and most other succulent groups.

One of the key attractions for Peter (as well as for other collectors) for growing Pachypodiums is that most of the species are easy to care for. Some species can actually be grown year-round under the elements in our country. These can take all the rain our tropical environment can offer. But care must be taken for other species as well, which will quickly rot just like most cacti if subjected to this kind of treatment. So it’s vitally important to know and understand which species you are growing.

The name Pachypodium comes from the Greek “pachy” (thick) and “podium” (foot), hence, “thick foot,” as most species are caudiciforms and have bottle-shaped trunks. Pachypodiums are a genus of about 25 to 30 species, the majority from Madagascar and some from southern Africa. Most are shrubs, but eight species form trees up to 20 feet tall. Pachypodiums are related to the genus Adenium but differ in that their branches and trunks are covered with strong spines. Adenium branches and trunks don’t have spines. The flowers, which are mainly yellow but also red and white in a few species, form only on mature plants that are around 10 years old or more. In the tree species, flowers only form when the plants have achieved a certain height.

The online encyclopedia Wikipedia has a great discussion on Pachypodiums: “The pachycaule trunk is a morphologically enlarged trunk that stores water so as to survive seasonal drought or intermittent periods of root desiccation in exposed, dry, and rocky conditions. Whereas there is great variation in the habit of the plant body, all Pachypodiums exhibit pachycaul growth. Variation in habit can range from dwarf flattened plants to bottle-shaped shrubs to dendroid-shaped trees.

The second general characteristic of Pachypodium is spinescence, or having spines. The spines come clustered in either pairs or triplets with these clusters often arranged in rings or whorls around the trunk. Spines emerge with leaves, and like leaves grow for a short period before stopping growth and hardening. Spines do not regenerate so weathering and abrasion can wear away all but the youngest spines from older specimens, leaving smooth trunks and branches.

To some extent, branches are a characteristic of the genus. Some caution is warranted in over-generalizing this characteristic.Pachypodium namaquanum is often branchless. Pachypodium brevicaule has no clear branches, and indeed may have evolved an alternative to branching in the form of nodes from which leaves, spines, and inflorescences emerge. In general, Pachypodiums have few branches. Since the environmental stresses and factors that contribute to branching can vary widely even in small areas, individual plants of the same species exhibit wide variation in branching morphology.

Unlike many members of the Apocynaceae, including some members of the superficially similar Adenium, Pachypodium species do not exude a milky latex. Rather, the sap is always clear.

One of the best sources and growers of Pachypodiums is Highlands Succulents in Ohio, USA. Highlands Succulents has been responsible for the propagation and distribution of Pachypodiums in the US. Many of their plants have also been sold worldwide (though the Nursery does not sell outside the US anymore). Based on their experience, they have found Pachypodiums to be robust succulents that rapidly respond to their growing environment and therefore require high light levels to keep them in check. These plants require as much direct sunlight as possible to keep their compact growth, their spines robust, and their trunks nice and fat. Most growers new to this genus are often amazed at the amount of water required.

I have been growing several species outside in my garden and without protection for several years now. These are mainly the tree-growing species such as P. lamerei, P. geayi, and the very rare P. menabeum. P. fiherense, which is more of a fat shrub, has also done extremely well under our tropical conditions. Madagascar, where more than 80 percent of all Pachypodiums are endemic, has a tropical to semi-tropical climate. So many (not all) of the Madagascan species do very well in our country.

The ones you have to be more careful about are species like P. namaquanum from Southern Africa. Too much water at the wrong time of the year will quickly transform this species into utter mush. P. brevicaule is also quite temperamental. When growing (you will know when these are growing because they will be producing new shoots and leaves), all Pachypodiums can take a great deal of water. But when these are resting (generally during the cooler months of the year), these plants will lose their leaves. It is during these times of the year where much less water should be given. 

For the sensitive species, I water twice a week when the plants are in active growth and only once a week when the plants are dormant. Pachypodiums can also be grown in richer soil (i.e., a mix of 1/3 good sandy garden loam, 1/3 good quality organic mix, and 1/3 pumice or washed river sand). This is a mix I use for Haworthias and Gasterias as well. Also, if you want your plants to produce fatter stems, it is better to underpot rather than overpot the plants. 

This is a fascinating group of African succulents with their different shapes, sizes, and growth temperaments which are highly recommended for all collectors, novice and the seriously-experienced!