This evergreen tree was selected to be one of the Trees of the Year for 2002. Pittosporum viridiflorum varies in size from a shrub of about 4m in height to a large forest tree of up to 30m. The bark is pale brown to greyish with distinctive white dots (lenticels). The leaves are usually wider above the middle, dark green and glossy. Small, greenish-white, sweetly fragant flowers are produced in early summer (November to December). They are followed by small, yellow-brown seed capsules. This plant is very showy when the capsules split open to release numerous small, shiny, orange-red seeds, which are covered in a sticky, resinous exudate. This cheesewood is often confused with the white milkwood (Sideroxlon inerme).

Pittosporum viridiflorum is widely distributed in the eastern half of South Africa, occuring from the Western Cape up into tropical Africa and beyond to Arabia and India.. It grows over a wide range of altitudes and varies in form from one location to another. Pittosporum viridiflorum grows in tall forest and in scrub on the forest margin, kloofs and on stream banks.

The name is derived from "Pitta" = pitch and "sporum" = seed (referring to the sticky seeds); and viridiflorum = with green flowers.

Many birds, including the red-eyed dove and several starlings eat the seeds. Goats and game (Kudu, Nyala, and Bushbuck) browse the leaves. The stem bark, which has a bitter taste and strong resinous or liquorice smell, is used medicinally. Decoctions or infusions are widely used to treat stomach complaints, abdominal pain and fever. It is said to ease pain and have a calming effect. Dried, powdered root or bark is sometimes added to beer as an aphrodisiac.

The wood is reportedly little used - being soft and white, which may account for the common name - cheesewood. However, Venter& Venter (1996) state that it is used for kitchen furniture and shelving.

According to Smith (1966), the name kasuur is a contraction of kaasuur, candle hour, which refers to the time the flowers exude their sweet fragrance. Smith also reports that Pittosporum viridiflorum is cultivated on St Helena, having been introduced by the Dutch in the 17th Century. It was also cultivated in Europe after being introduced probably by Masson.

Growing Pittosporum viridiflorum

This plant makes a good garden plant, growing in either in full sun or semi-shade. It makes a well-shaped, medium-sized tree or can be pruned as a hedge. It is useful for screening and can also be grown in a big container as a patio plant. It is hardy, neat and undemanding and makes is an ideal plant for a small, town house garden as it does not have a aggressive root system. Not only does it have fragrant flowers to scent the evening garden, it is also colourful when in fruit and attracts birds to the garden.

Cheesewood propagates easily from seed. Unparasitised seed has a germination percentage of 80-90%. Sow seeds in trays in a mixture of river sand and compost; cover lightly with fine compost and keep moist. Seeds should germinate in 8-12 weeks and the fast growing seedlings should be bagged up when they have two leaves. Plants may also be propagated by means of softwood or semi-hardwood cuttings. This plant transplants easily.

Pittosporum viridiflorum can withstand some frost and cold and is fairly drought- resistant, but prefers well-drained soils and a reasonable amount of water.

The common pittosporums in the horticultural trade come from Australia, New Zealand and the Far East. Pittosporum undulatum from Australia is now listed as a Category 1 Invasive Plant and may not be cultivated in South Africa.

References

• Palmer, E. & Pitman, J. 1972. Trees of Southern Africa. Balkema, Cape Town.
• Coates Palgrave, K. 1983. Trees of Southern Africa. 2nd ed. Struik, CapeTown.
• Van Wyk, Ben et al. 1997. Medicinal Plants of South Africa. Briza, Pretoria.
• Coombes, Allen, J. 1992. Guide to Plant Names. Hamlyn, London.
• Smith, C. A . 1966. Common names of South Africa Plants. Botanical Research Institute, Pretoria.
• Venter, F. & Venter, J-A. 1996. Making the most of indigenous trees. Briza, Pretoria.

Thompson T. Mutshinyalo
with additions by Yvonne Reynolds
Witwatersrand National Botanical Garden
January 2002