Pachypodium (2007)

By Pam Schnebelen (October 2007)

Pachypodium is in the family Apocynaceae, along with another favorite succulent genus, Adenium, and a popular semisucculent genus, Plumeria. These plants have showy and attractive flowers in many colors. All plants in this family have common flower and fruit characteristics. Except for the pair of carpels in the ovary, flower parts are in fives. Seeds are packed into large two-part fruits and have a single tuft of hairs. As in the Asclepiadaceae, the fruits ripen into a pair of “horns.”

The name Pachypodium means “thick foot,” a reference to the plants’ thick trunk and stems. Tissues are soft and watery. Even very large and old specimens have little tissue that we would call “woody.”

Species come in a variety of shapes and forms. All have leaves and spines. Treelike species include Pachypodium lamerei (Madagascar), P. geayi (Madagascar), P. rutenbergianum (Madagascar) and P. namaquanum (Namaqualand).

Shrubby forms include Pachypodium densiflorum (Madagascar), P. horombense (Madagascar), P. ambongense (Madagascar), P. decaryi (Madagascar), P. baronii (Madagascar) and P. lealii (subspecies lealii in Namibia and Angola, and subspecies saundersii in Zimbabwe southwards to Kwazulu-Natal).

There are two geophytic forms: Pachypodium bispinosum (eastern Cape) and P. succulentum (central and southern Cape, northwards into the free state). These species have many branched above-ground stems and a fat below-ground caudex. In captivity, most of us raise the caudex for its artistic effects and prune the stems to encourage branching and a brushy appearance.

On the short end of the height scale is Pachypodium brevicaule, literally “thick foot, short caudex.” This plant has a thick pancakelike shape, hugging the ground as it grows laterally. A lithophyte that grows on rocks, P. brevicaule has a well-deserved reputation for being difficult to cultivate. It does not tolerate cold or wet conditions and is frequently grafted to increase viability.

Cultivation
Heat and light are absolutely critical in growing pachypodiums. When they are actively growing, they should be watered thoroughly as soon as the mix dries out. Some of the larger Pachypodium species do best when watered several times a day. I remember discussing P. lamerei with a commercial grower who had timers set to water the plants eight times a day!

These plants will not go dormant if kept in full sun and over 60 degrees F all year. Few of us can provide those conditions, so we keep the plants dry and dormant in winter.

They need a porous mix, one with a lot of air and excellent drainage. Plants should only be fertilized when they are actively growing.

Propagation
Apocynaceae are generally self-incompatible, so two different plants are needed to produce seed. Raising plants from seed is fairly easy. Seeds must be fresh, and seedlings must be kept warm, wet and humid.

Producing plants from stem cuttings is possible, but I have had little success. This method is known to be impossible with Pachypodium brevicaule and P. namaquanum. Root cuttings can be taken from P. succulentum.

Slower-growing pachypodiums are frequently grafted to get faster growth. P. lamerei is very easy to grow and is a common stock plant for grafts.