Pachycauls are plants with a disproportionately thick trunk for their height, and few branches.[1] In contrast, trees with thin twigs such as Oak (Quercus), Maple (Acer) and Eucalyptus are called leptocauls while those with moderately thick twigs like Plumeria are called mesocauls. Pachycauly can be the product of exceptional primary growth (as with palms and cycads) or disproportionate secondary growth as with the Baobabs (Adansonia). The word is derived from the Greek pachy- meaning thick or stout, and Latin caulis meaning the stem.[2] All of the tree (and treelike) species of cactus are pachycauls, as are most palms, Cycads and pandans. The most extreme pachycauls are the floodplains, or riverbottom variety of the African Palmyra (Borassus aethiopum) with primary growth up to seven feet (2.1 meters) in thickness,[3][4][5] and the Coquito Palm (Jubaea chilensis) with primary growth up to six feet (1.8 meters) thick.[6][7][8] The most pachycaulous cycad is Cycas thouarsii at up to five feet (150 centimeters) in diameter.[9] The tallest pachycaul is the Andean Wax Palm (Ceroxylon quindiuense) at up to 220 feet (67 meters).[10] and about 16 inches (41 cm) in diameter. The most pachycaulous cactus is the Bisnaga (Echinocactus platyacanthus) with primary growth up to 4 ft 4 in (1.32 meters) in diameter.[11] The largest caudex type pachycaul is the African Baobab (Adansonia digitata). One called the Glencoe Baobab at Hoedspruit, South Africa has a basal diameter (not girth) of 52 ft 2 in (15.90 meters).[12] This tree suffered a severe trauma and is dying.
Examples occur in the genera[13]