Although the plants are very variable in almost all respects, they are always completely and densely covered with white to reddish hairs (except the inside of the flowers).
They have erect to creeping stems, 0.5-1.2 m tall and with egg-shaped to round leaves 16-40 cm long and 0.6-3 cm wide, often with an auriculate* base. The upper leaves are stalked, the ones near the base without stalks.
The inflorescenses are 15 cm wide and produce bulbils; the flowers have 1.4-3 cm long tubes and are red, pink, or yellow, often with red stripes.
The species occurs in central, eastern and northern Madagascar, usually on damp or wet rock surfaces.
Several varieties have been described, but they are not upheld in the Illustrated Handbook of Succulent Plants.
*auriculate: with small roundish or ear-like appendages.
Plants photographed in June 2017
Here the trunk is only to about 1 m tall and to 50 cm in diameter, conical to irregularly pyramidal, with silver-grey bark.
The branches are hairless, often strongly zig-zag and frequently terminating in a sharp spine; the leaves are 1.5-3.6 cm long with 3-4 (sometimes 5) pairs of leaflets which sometimes touch each other.
The flowers are yellowish-green.
The species has a limited distribution around Toliara, at altitudes from sea level to 500 m, growing in dry thickets on limestone. It is known from only 5 localities and considered endangered. This situation is exacerbated by collection of wild plants.
This species was only described in 1995 and before that time was usually misnamed O. decaryi.
Operculicarya consists of 5 species of deciduous shrubs or small trees with conical or irregularly swollen trunks, warty-bumpy bark and gnarled branches. The genus is endemic to Madagascar and belongs to the Anacardiaceae, a family of over 800 species mainly occurring in the tropics and subtropics, including well known crop plants such as pistachio, cashew nut and mango.
O. decaryi is the most widespread of the genus and occurs in dry forests in the southwest and south of the island.
It can be a small shrub or a tree, up to 6 m or more tall, with tuber-like roots*. The trunk may be parallel-sided, bottle-shaped or conical, is up to 1 m in diameter and has silver-grey or dark grey bark.
The twigs are slender, more or less straight to strongly zig-zag; young ones sometimes hairy. The leaves are 2.5-6 cm long with 4-9 (usually 5-7) pairs of leaflets, which do not touch each other.
The bright to dark red flowers are either male or female.
Like O. pachypus, the plants are becoming increasingly rare in the wild and are listed in Appendix II of CITES.
* these can be used for root cuttings.
In the wild (the dry spiny forests of western and southwestern Madagascar), one often sees these plants growing on top of shrubs and small trees.
The climbing or creeping branches are up to 5 m long; they bear few tendrils, which are branched at their tips and grey-green leaves, which are 3.5-5.5 cm long and 2.5-5 cm wide.
The inconspicuous flowers are greenish-yellow.
Over a period of hundreds of years, a great part of the original forest vegetation of Madagascar’s Central Plateau has been destroyed by annual burning.
The resulting savannah-like grasslands are very poor in species. A few succulents can survive the fires, either because they have very thick and fleshy leaves, e.g. the subject of this post, or because they hide underground (such as geophytic Euphorbias, see Euphorbia primulifolia).
A. macroclada is an impressive plant with its leaves up to a meter long and 17-22 cm wide at the base. In winter, the stemless rosettes are adorned with (usually single) inflorescences which in old specimens may be up to 2.5m tall. The many flowers are 2-2.5 cm long and 2 cm wide at the mouth.
It is probably the most widely distributed of the Madagascan Aloes, from 200 km north of Antananarivo to Fort Dauphin in the far south, usually at altitudes between 1200 and 1500 m.
There is only one place in the world where this species is known to occur: Tanjona Vohimena, the southernmost tip of Madagascar*.
On this stark, wind-swept limestone terrace about 100 m above sea level, the species occupies an area of less than a km².
Old plants possess a large turnip-shaped root to 30 cm long and to 10 cm wide, topped by a densely branched crown to 30 cm in diameter. In habitat the branches creep along the ground as a result of the constant wind; in cultivation they are more or less erect.
The leaves form rosettes at the tips of the branches, they are to 25 x 8 mm in size and green to red-brown.
* The old name for this is Cap Sainte Marie, which explains the specific epithet.
Plant in cultivation; scanned slide
In the dormant state, without leaves and flowers, this species is difficult to distinguish from P. densiflorum and P. rosulatum. They share the same habit: low, multi-branched shrubs up to 1.5 m in diameter and up to 1 m tall.
P. horombense is named after the Horombé plateau in the southern highlands of Madagascar, where it often occurs in great numbers on granite rocks.
The inflorescence has an erect peduncle of no less than 60 cm tall, with broadly cup-shaped flowers 1.7-2.3 cm in diameter.
According to Werner Rauh in his great book on the succulents of Madagascar, this is:
“the most beautiful Pachypodium species in cultivation”.