Pachypodiums are members of the Apocynaceae family which also includes Adeniums, Oleanders, Plumeria and Periwinkles. Pachypodium genus contain 25 species, from mostly arid regions of Namibia, Zimbabwe, Boswana, Angola, South Africa and Madagascar. Pachypodium means ‘thick foot’, referring to the large, swollen caudiciform stems all members of this genus have. They have succulent stems and most are heavily armed with thick, stiff spines on the caudex and branches. Leaves are only present on the top of the caudex or near the ends of each branch. The palm-like look of some species is where the name Madagascar Palm comes from. The flowers of the genus are simple, star shaped and somewhat similar to Plumeria or Oleander flowers and some fragrant.

In general the Madagascar Palms are easy plants to grow indoors, and even easier outdoors in the warm and dry climates. Some Pachypodiums even do well in warm and humid climates like Pachypodium lamerei and P.rutenbergianum.

Pachypodiums are summer growers, they are fully leaved and growing the most vigorously at summer and autumn. Most species are deciduous and lose their leaves in winter. They do not need water in winter. Soils have to be very well draining or these plants will rot if kept wet too long in poorly draining soils.

Madagascar Palms are full sun plants in the wild demanding of high light situations and suffer in dark, shady locations. Pachypodiums are not cold tolerant plants. Pachypodium lamerei, P. geayi, P. lealii and P.succulentum are the most likely species to do well outdoors. Most other species are usually grown in pots. Frosts down to -3°C or below will usually cause severe damage to the trunk.  Fertilizer is not usually needed if one is going to repot their plants every 2-3 years. It is recommended to use a standard fertilizer that has even quantities of all three major nutrients.

PACHYPODIUM LAMEREI is the most commonly grown Pachypodium in cultivation and the one most refer to as the Madagascar Palm. It is one of the faster growing species, obtaining heights around 600 cm in its native southern Madagascar and is a thick-trunked, intensely spiny tree with some branches. The spines are usually about 2-3 cm long, fairly sharp. The leaves are lancelote and bright green with a pale yellow midrib. Branching usually occurs as a result of injury like trauma, frost damage, insect damage etc. Flowers occur usually in early summer and are white with yellow centers and smell very nice. It is one of the easiest succulents to grow, both in the ground and in a pot. Pachypodium lamerei also do well in humid climates.

PACHYPODIUM GEAYI is also called the Madagascar Palm, and is also from Southern Madagascar, though from a more arid climate zone there. In general appearance it is somewhat similar to Pachypodium lamerei, but tends to be more robust and taller. The primary difference between the two is this species has thinner, greyer-green leaves that are less shiny and have a reddish midrib. This plant prefers a drier climate, not the humid ones Pachypodium lamerei seems to prefer.

PACHYPODIUM RUTENBERGIANUM is the largest and fastest growing Pachypodium, can reach 900 cm. high. But it is also a bit less hardy and touchier. Flowers are white with pale yellow centers, but seem to form while leafless in winter, instead of in summer like the above two.

PACHYPODIUM NAMAQUANUM is the largest of the species and the one originally referred to as Halfmens. In Africa these plants can grow as tall as 300-400 cm, but they are pretty slow growing even there. In cultivation they rarely get taller than 100-120 cm. Branching is rare and few plants have more than 2-4 branches. The leaves are pale green and characteristically fuzzy with curious undulating margins. Flowers are deep red color and form at the top, center of each stem in tight bunches. Old plants are wonderfully impressive landscape specimens, most grow this species in pots.

PACHYPODIUM SAUNDERSII can reach 120 cm height. It is a highly branched plant eventually forming an irregular and somewhat awkward looking shrub. Flowers are white in the late summer to autumn. Plants as young as 4 years can flower.

PACHYPODIUM LEALII the leaves are less shiny, to nearly fuzzy. This species is a bit less branched, but similar in overall shape to Pachypodium saundersii. The flowers have distinct pink throats. Cold hardiness is pretty good down to about -3°C.

PACHYPODIUM SUCCULENTUM this is probably one of the ‘hardy’ Pachypodiums, that at least can be grown reliably in the ground of warm temperate climate zones. It is nearly a geophyte with its huge, bulbous caudiciform roots being all underground in nature. However, in cultivation most grown with the majority of roots above ground for effect. Flowers are in late spring to early summer and are tiny, white with pink midribs.

There are about 18 other species of Pachypodium, all worthy of pot culture as most are wonderfully ornamental caudiciform plants. If you wish more information for Pachypodiums: refer to Geoff Stein’s excelent article at Dave’s Garden>>> http://davesgarden.com/guides/articles/view/539/