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.
Based on genetic research, in 2013 Ronell Klopper and Gideon Smith created the genus Aloidendron to accommodate 6 species of tree aloes, including Aloe dichotoma.
The plants form trees with a rounded crown, with stems to 1 m in diameter at the base and usually 3-4 m tall (sometimes up to 9 m).
The bark on the trunk peels lengthwise, forming large scales with hard and razor-sharp edges. The leaves are about 30 cm long and 5 cm wide at their base.
In winter (May-August), the flowers appear; they are pollinated by starlings, sunbirds, weaver birds and white-eyes.
From the Brandberg Massif in Namibia to Upington, Kenhardt and the Nieuwoudtville area in South Africa, the species forms a conspicuous component 0f the landscape. The plants occur in open sites, usually in rocky terrain but also in flats.
Depending on the area, rainfall (between 50 and 300 mm per year) may occur in either summer or winter.
Both the scientific and the vernacular name (Orange River Aloe) refer to its occurrence along the Orange River (from Grootderm in the west to Keimoes in the east). It is also plentiful in the Warmbad area of Namibia. The plants are usually found in steep rocky places and are rather variable, depending on the locality.
Usually solitary, the plants are stemless or short-stemmed (up to 1 m tall).
The leaves are 30-40 cm long and 5-8 cm wide near the base, incurved, dull yellowish-green to reddish-brown with numerous longitudinal lines. In young plants they are
copiously spotted on both surfaces, later on they only have some spots on the upper surface. The margins have small, sharp teeth, but otherwise the leaves are unarmed.
The unbranched inflorescences are up to 1.2 m tall and bear flowers from July to September. These are usually yellow to greenish yellow, but in the eastern part of the distribution area sometimes reddish.
This very distinctive species normally produces one single stem up
to 8 m tall and only 10-15 cm thick. Sometimes, plants branch from the base and form large shrubs.
Each stem bears about 25 leaves, up to 90 cm long and grey-green on both sides; the sap is poisonous.
The inflorescences are much-branched, with carmine to reddish-orange flowers.
The species is found in more or less dense bushland and thickets along rivers in
southern Kenya and northern Tanzania at altitudes between 900 and 1500 m.
This is one of the very few southern African Aloes without spines on the edge of the leaves.
The stems are rarely over 30 cm long and the leaves are up to 60 cm long and 15 cm wide, from greenish-grey to pinkish-grey with not very distinct longitudinal stripes.
The flowers are bright orange or (rarely) yellow on inflorescences up to a meter tall and appear from winter to early spring (August-October).
On flats with deep loamy soils, the plants are often abundant, but they also occur on rocky slopes.
The plants are not grazed, so when you see a great many together, this is an indication of heavy overgrazing of the area in the past. They are widespread from Worcester in the Western Cape to Queenstown in the Eastern Cape.
In general, this species is stemless and growing singly or in small groups, but sometimes groups of over 20 rosettes are formed.
Each rosette has 14-16 leaves, about 16 cm long and 6 cm wide at the base, usually olive-green with many whitish-green spots, but in some cases light green and unspotted.
The flowers are very striking and because of their conspicuous stripes apparently unique within the genus.
The plants occur on gypsum soil in the Al Madu (Ahl Medow) Mountain Range (north of Erigavo) in Somaliland, at 1,500 to 1,550 m, mostly in shade.
Aloe somaliensis was described in 1899, from plants that were raised at Kew from seeds that had been collected a few years before, probably at Sheikh pass in Somaliland Protectorate (as it was then called). It is now known to occur not only in Somaliland but also in Djibouti, on rocky slopes at altitudes between 700 and 1700 m.
It may be of interest to know that the accompanying pictures were taken late January 2015, likely at roughly the same spot the original seeds came from.
The plants grow singly or in small groups and bear 12-16 leaves, usually narrowly lance-shaped and about 20 cm long.
The inflorescences are 60-80 cm tall.