Pachypodium brevicaule

P. brevicaule Bak. in J. Linn. Soc. 22: 503, 1887

Least in stature, but certainly not in interest, comes the midget of all pachypodiums and one that exerts great attraction on collectors, although it is neither cheap nor easy to obtain. The plant body shows the ultimate in compression, beginning in seedlings as a sphere and later broadening and becoming lobed like a low, flat cake rising only a few centimetres above the soil. It is a lithophyte, growing naturally in full sun on bare rock faces, and mature specimens, which must be of great age, are reported 60-100cm in diameter and aptly described by Rauh as resembling a pile of potatoes, the silver-skinned surface closely resembling that of the rock background. It is not difficult to see how its unique appearance could have evolved from a plant with the habit of P. decaryi by telescoping of the branches, which rise no more than a few centimetres above the surface of the flattened body and carry the leaves and spines superposed so as to appear like rosettes.

The leaves are elliptic, like those of privet, dark green and almost sessile, 2-4cm long and up to 16mm wide and are puberulent, at least when young. The spines are only about 3mm long, soft, white and pubescent.

The brilliant yellow flowers, large for the size of the plant that bears them, are borne on condensed cymes of 2-6 on peduncles 2 or rarely up to 5cm tall. The cylindrical upper tube is 15-25mm long, and the five spreading lobes are obovate and rounded, only slightly asymmetric and 15mm long by 12mm wide. The twin fruits are cylindrical and hairy, up to 10cm long.

Exhibition plant of Pachypodium brevicaule, raised from seed, in a 20cm pan.

P. brevicaule ("short-stemmed") was originally maligned as impossible to re-establish as imports, unbearably slow-growing from seed, delicate and reluctant to bloom or set seed. Dedicated growers have proved all these assertions to be false. Seedlings kept warm and well fed form a recognizable caudex the first year and flower the second. Seedlings grafted on P. lamerei grow even faster, as I can testify from personal experience. Domestically produced seed is now available, so that there is absolutely no excuse for the habitat-stripping that has been, and may still be, going on. It is sensitive to cold, waterlogged conditions and should be kept warm at all times and given extra well-drained soil. The leaves fall completely in the resting period, when watering should be reduced to a minimum. P. brevicaule was offered as ISI 1406 in 1983.

Lavranos and Röösli (1996) declare P. brevicaule to "prefer poor, well-drained sandy or gravelly soil", but I suspect that it is found in such inhospitable areas not by choice but only as a result of competition: in more fertile areas other plants would oust the dwarf, slow-growing pachypodiums. Certainly in cultivation they respond to nutritious "cactus compost" and grow much faster.

Rauh (1972) found a wild hybrid, presumed to be with P. rosulatum and intermediate between the two species, which overlap in range. Another spontaneous hybrid, this one between P. brevicaule and P. densiflorum, has been described and illustrated by Halda (1997), who named it P. x rauhii in honour of Prof. Rauh who has done more than anyone to locate, introduce and document the Madagascan pachypodiums.

(Left) Year-old seedling of Pachypodium brevicaule grafted on Pachypodium lamerei. (Right) Well established plant of Pachypodium brevicaule in a collection in California.