Regarded as the largest succulent plant in the world, it is a tree that can provide food, water, shelter and relief from sickness. Although baobabs seldom exceed a height of 25 m, the main stem of larger baobab trees may reach up to 28 m in girth. The squat cylindrical trunk gives rise to thick tapering branches resembling a root-system, hence the name "Upside-down Tree". The stem is covered with a 50-100 mm thick bark layer, which is greyish brown and normally smooth but can often be variously folded and seamed from years of growth. The leaves are said to be rich in vitamin C, sugars, potassium tartrate, and calcium. They are cooked fresh as a vegetable or dried and crushed for later use by local people. The off-white, powdery substance in the fruit is apparently rich in ascorbic acid, and is soaked in water to provide a refreshing drink somewhat reminiscent of lemonade. This drink is also used to treat fevers and other complaints. The sprout of a young tree can be eaten like asparagus. The root of very young trees is reputed to be edible. The seeds are edible and can be roasted for use as a coffee substitute. Caterpillars, which feed on the leaves, are collected and eaten by African people as an important source of protein. When the wood is chewed, it provides vital moisture to relieve thirst, humans as well as certain animals eat it in times of drought. This tree is slow growing, mainly due to the low rainfall it receives. Large baobab trees with hollow stems have been used by people for various purposes including houses, prisons, pubs, storage barns, and even as bus stops.