Osyris compressa, previously known as Colpoon compressum is a very decorative and useful plant in cultivation as well as in its natural habitat. It is a hemiparasitic plant, in other words a plant that is capable of producing its own food (photosythesis) as well as utilizing nourishment from a suitable host plant by means of parasitism. This together with some other interesting features, makes the Cape sumach a highly successful species in the Cape Floristic Region and in other vegetation types.
Osyris compressa is classified as a shrub although it can attain the size of a small bushy tree of 1-5 m in height. It is a partial parasite on the roots of plants. The Cape sumach has a smooth greyish bark and the leaves are opposite, stiff, erect and crowded up the stem.The elliptical leaves which are tough and leathery are 10-50 x 10-27 mm, and blue-green with a grey bloom.
The flowers are small, about 2 mm across, yellowish green, slightly scented, inconspicuous and are borne in small terminal heads or panicles. Flowers are either just male on one plant or hermaphroditic (can be male or female on the same plant). The flowers and fruits are produced erratically throughout the year, but mainly from April to December. The fruits are highly decorative on the plant and are ellipsoid (elliptic in long section and circular in cross section), fleshy, about 15 x 10 mm, becoming bright, shiny red and then purplish black. Fruits don't ripen all at once which is why these plants can be very attractive for long periods throughout the year.
Osyris compressa is a very tough and well-established plant in its native habitat. The plants are relatively short-lived but highly developed as can be noticed by the abundance of fruits each plant produces throughout the year, enabling it to secure maximum offspring. Its semi-parasitic lifestyle also gives it an added advantage over other plants. Osyris compressa is not threatened or in danger of becoming threatened.
Distribution and Habitat
O. compressa occurs on coastal dunes and inland slopes from the Cape in the south to Kosi Bay on the east coast. Associated biomes include mountain and coastal fynbos as well as savanna habitats. Plants thrive in sandy conditions and together with other species of plants forms an important soil stabilizer in coastal dune systems. All species of Osyris grow in close proximity to other plants; in the Fynbos Biome these may be species of Rhus, Coleonema, Maytenus, Leucadendron, Metalasia and Chrysanthemoides.
Derivation of name and historical aspects
The generic name is from the Greek ozos and means branched, referring to the branching habit of the plant. The specific ephithet compressa means laterally flattened. The tree is closely related to an inland species namely Osyris quadripartita ( Transvaal sumach), previously known as O. lanceolata but the latter can easily be recognized by the alternate leaves and the axillary flowers.
Osyris compressa is designed for survival. Its blue-green, leathery leaves enable it to withstand heat and wind intensities normally associated with the coast. It is a fast grower and establishes itself rapidly through masses of seeds, which are produced for at least eight months of the year.
As it is hermaphroditic, the plant has a much greater chance of producing viable seeds faster and it ensures that cross pollination takes place between separate plants which creates a stronger gene pool for the species.
The scented flowers attract insectiverous pollinators ranging from bees, butterflies, flies and ants. O. compressa is also an important food plant for the larvae of the Common Dotted Border (Mylothris agathina ), a yellowish, medium-sized butterfly that occurs along the coast. The glossy green berries grow fast and become dark red to purple by which time they fall to the ground. Many different birds feast on these berries and in so doing ensure the effective spread of the plants.
As with the other member of the Santalaceae family, the Cape sumach parasitizes nearby plants by means of root attachments. The young plant may utilize water and important nutrients from the host plant, and may become less dependent as it matures; the plant is not entirely dependent on host plants and can survive on its own should the host plant die until another suitable host is found. There are no known benefits to host plants once they have become parasitized.
Uses and cultural aspects
The fresh leaves of Osyris compressa were used to tan leather a light brown colour, while the bark was used to tan leather dark brown. A layer of crushed leaves or bark, depending on colour preference, was put into the bottom of a trough, and the hide, with hair removed, was placed on top of the plant material. Successive layers of plant material and hides were made, and the wet mass was pressed flat with weights and left to tan for two weeks before removing and drying. A decoction of fresh leaves was used to tan cotton, fishing lines and nets to make them more durable in the days before nylon.
The wood is heavy and fine-grained, but because of the small size of the tree, it is suitable only for ornaments. The fruits are edible and were an important food of the early inhabitants of the Cape. The stones were removed and the fleshy part compressed and stored for lean times.
Growing Osyris compressa
Plants grow from seeds which fall to the ground. Seeds can be sown in situ (directly in the open garden), if there are other plants to serve as the hosts. It is not possible to grow plants from cuttings. Osyris is not well established in cultivation and best left to reproduce naturally. Plants do exceptionally well in coastal areas and are very tolerant of windy conditions. It is recommended as a seaside subject and plants form very effective small windbreaks provided there are enough host plants. They also attract birds and insects to the garden and do well with the other more common Coastal Fynbos vegetation from the Asteraceae, Rutaceae, Proteaceae, Anacardaceae.
References and further reading
- Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of southern Africa, edn 3., Struik, Cape Town.
- Fox, E.W. & Norwood Young, M.E. 1982 Food from the Veld, Edible wild plants of southern Africa. Delta Books (Pty) Ltd, Johannesburg.
- Germishuizen, G. & Meyer, N. (eds).2003. Plants of southern Africa : an annotated checklist. Strelitzia 14. National Botanical Institute, Pretoria.
- Jackson, W.P.U. 1990. Origins and meanings of South African plant genera. University of Cape Town Ecolab.
- Leistner, O.A. 2005. Seed plants of southern tropical Africa : families and genera. SABONET, Pretoria. Mason, H. 1972. Western Cape Sandveld flowers. Struik, Cape Town .
- Smith, C.A. 1966. Common names of South African plants. Memoirs of the Botanical Survey of South Africa No. 35. Stearn, W.T. 2003. Stearn's dictionary of plant names for the gardener. Cassel , UK .
- Van Rooyen, H. & Steyn, H. 1999. Cederberg. South African Wildflower Guide 10. Botanical Society of South Africa, Cape Town.
- Van Wyk, B-E. & Gericke, N. 2000. People's plants. A guide to useful plants of southern Africa. Briza Publications, Pretoria.