Dioon spinulosum

Dioon spinulosum, the giant dioon, is an exotic cycad seen growing in the Stellenbosch University Botanical Garden. It is one of the tallest cycads on earth, reaching heights around 12 m. The stocky, cylindrical trunk is up to 40 cm in diameter, usually growing single-stemmed.

The pinnate, usually blue-green leaves grow from 1,5 m to 2,1 m long, radiating from the upper part of the trunk. There may be up to 240 leaflets on each leaf. The sessile leaflets are small, flat and acutely pointed with spines along their margins.

The dioecious tree grows male or female stem-tip cones instead of flowers, in keeping with the habits of its family, the Zamiaceae. The peak time of flourishing of these trees on earth is said to have been before 170 million years ago.

In nature, the species is found in Mexico. Its habitat is low elevation, tropical rain forests on limestone cliffs and rocky slopes. It copes with low temperatures, although the shape of the flourishing, evergreen gum palm suggests the tropics (Wikipedia; www.gardenia.net; http://llifle.com).