Screw pine
The genus name, Pandanus, is derived from one of the plant's Malayan names, pandang. There are over 650 Pandanus species distributed through Tropical Africa, Asia and Australasia. Generally species grow in coastal areas and on islands. Because of the way some Pandanus species grow they produce impenetrable clumps, and are frequently used to control coastal erosion; in a similar way mangroves are used. Screw pines are also used as windbreaks and natural fences.
The common name 'screw pine' comes from the screw-like arrangement of leaves as they come off the main stem or trunk. This feature becomes more obvious as individual plants mature. The leaves are sword-shaped and very heavily armed, with sharply-toothed edges and midribs. As plants age, they develop large prop roots, which support erect stems and branches. In effect, these are suckers so the plant spreads and clumps become denser and denser. The plants are dioecious, that is, male and female flowers are produced on the different plants. The female flowers are arranged in a cone-like manner, whilst the male flowers are produced in a panicle. The fruits are woody drupes, often pendulous and look a bit like pineapples. In many species these fruits are edible. The leaves are sometimes used as thatching material or woven into ropes, baskets, hats and mats.
Madagascar is home to Pandanus species, including Pandanus utilis. In the wild, the endemic orchid, Eulophiella roempleriana, is an epiphyte specific to Pandanus utilis.
As they are vigorous plants, if screw pines are to be grown in temperate climates, a decent-sized glasshouse is needed. They prefer good light, although the plant at Oxford Botanic Garden grows in the Palm House, which has a lot of shade cast from surrounding plants. Minimum temperatures of 13-16 degree Celsius are preferred, but some species will tolerate cooler temperatures for short periods. The Palm House screw pine has been in the collection since 1989, and is a fairly large specimen, being about two metres across and 1.5 metres high. As yet no prop roots have been produced, but the typical arrangement of spiralling leaves can be seen. When working on this bed care is needed else one may become painfully aware of just how sharp the edges of screw pine leaves can be. Cultivation of screw pines present few problems in terms of pests and diseases, although scale and mealy bug may become issues if not kept under control.
Further reading
Baines T 1894. Greenhouse and stove plants. John Murray.
Beckett KA 1987. RHS Encyclopaedia of houseplants. Swallow Editions Ltd.
Huxley A 1999. The new Royal Horticultural Society dictionary of gardening. Groves Dictionaries Inc.
Lucinda Lachelin