Hoodia (Trichocaulon) alstonii

Of the small-flowered Hoodias this is by far the tallest, with plants growing into many-stemmed shrubs up to slightly over a meter tall and 0.5 m wide.
The stems have an unusual whitish, grey-green colour and their 20-22 obtuse angles are armed with exceptionally hard and sharp spines.
The upper parts of the stems produce large numbers of flowers 1-1.8 cm in diameter.
The species has an unusual distribution. It occurs in the winter rainfall area of
Namibia on stony hillsides east of Luederitz and along the lower reaches of the Orange River.
In South Africa it also occurs along the lower Orange River: the western part of the area here receives rainfall in winter, whereas in the eastern part the rain falls in summer.
These habitats are surprisingly arid and in general the plants grow in the open on either rocky slopes or stony, flat areas.