This slender Tree may reach 15m high and has watery latex. The simple Leaves are alternate. The small, monoecious, unisexual Flowers occur in spikes at branch ends. Fruit is a 3-lobed dehiscent capsule.
Croton gratissimus var. gratissimus, Croton subgratissimus, Croton microbotryus, Croton zambesicus.
RSA Tree No. 328, 328.1
Common names: Berg-boegoe, Kalahari-boegoe, Lavender Croton, Lavender Fever-berry, Lavender fever berry, Laventebos.
Conservation Status: L C. (Least Concern). 2009 (Raimondo et al.).
Family: Euphorbiaceae (Euphorbia family e.g. exotic poinsettia – Euphorbia pulcherrima). This family has about 275 genera and 7 500 species. Our local genera containing trees include Alchornea, Croton, Euphorbia, Macaranga and Spirostachys. This family has plants that may be herbs, shrubs or trees and latex is often present. Leaves, when not rudimentary, are usually alternate and simple with free stipules. Inflorescences are situated terminally or axillary. They are mostly in cymes (a broad, more or less flat-topped, determinate flower cluster, with central flowers opening first). They may be grouped in spikes (simple indeterminate inflorescence with sessile flowers on a single unbranched stalk), thyrses (the main axis grows indeterminately, and the branches have determinate growth) or pseudanthia (inflorescence with many flowers appearing as a single flower – like a sunflower). In Euphorbia they appear as cyathia (where they usually have 5 joined bracts outside: up to 10 brightly coloured nectar glands which may have petal-like appendages or brightly coloured bracts followed by 5 much reduced male flowers at the base of each bracteole. In the centre is a much-reduced female flower). Plants may be monoecious or dioecious and the regular, unisexual Flowers may or not have a perianth. Male flowers have 1-many stamens with free filaments and stamens with up to 4 pollen sacs. Female flowers have a superior ovary with 1-many locules – each with up to 2 ovules. Fruit is a capsule or nut(s). Seeds may have a caruncle (a fleshy structure attached to the seed) and may be poisonous.
Name derivation: Croton: resembling ticks – referring to the seeds of some species. gratissimus means very or most pleasant. Var. gratissimus has no hairs on upper leaf surface. William John Burchell first named this plant. From 1811 – 1815 he travelled with his dog over 7 200km having never spent a night out in the open before. He collected 40 000 specimens which are now housed at Kew, as are his manuals containing the plant details. P&P think it is the best journal ever written by early travellers on South Africa. The Genus Croton has 13 tree species in the RSA.
Description. The Tree is not succulent nor cactus like. It grows as a shrub or tree up to 15m – taller to the north of RSA. It is usually a slender tree but may become spreading. Young branches are pale white to yellow or light brown and may be covered with cinnamon coloured dots, as are the leaves. The many brittle branches may droop. The rough and corky Bark is quite pale to dark grey. It is and fissured at the base. The tree possesses watery latex.
The simple, alternate Leaves tend to droop. They have some striking colours: silvery, gold, mauve and pink. Some leaves are red and glint in the sun. They are fragrant when crushed (similar to lavender) due to the presence of aromatic oils. Leaves are lanceolate to elliptic, variable in size up to 18 x 6cm but usually under half this size. The leaf is not rough to the touch. The surface is shiny dark green to olive green above and may have white visible gland dots. When these dots appear in great numbers, the under-surface may appear red-brown. The impressive surface below is very pale and or silvery and is covered with dense, small cinnamon-coloured star-shaped hairs (glandular scales). These hairs can be seen in photo 21. The 8-17 pairs of lateral veins are hardly visible. They become more visible when viewed against a strong light (photo 137). The Apex is tapering to broadly so. The Base from above appears to be perched on the petiole. It is rounded or notched to lobed, and has 2 small glands next to the petiole. The Midrib prominently protrudes below and is sunken above. The Margin is entire (with a continuous margin, not in any way indented) and may be wavy. The Petiole (leaf stalk) protrudes below and is up to 7cm long. From below, it appears pale yellowish or greenish even red to brown and may be covered with the same cinnamon coloured dots as the leaf blade. Variety gratissimus differs by having no hairs on the upper leaf surface whereas the upper leaf surface of var. subgratissimus has stellate hairs. Some orange leaves may be present.
The cream to reddish brown sweet smelling Flowers are unisexual and grouped in Spikes (simple indeterminate inflorescence with sessile flowers on a single unbranched stalk) up to 15+cm long. The small flowers (up to 6mm in diameter) tend to droop and are monoecious (separate male and female flowers present on the same tree). Strings of Buds may also be covered with dense, small cinnamon-coloured glandular Scales and may remain on the tree for months – usually until the rainy season when they develop into flowers at branch ends. The few Female flowers are located at the base of the spike are relatively large. The superior Ovary has 3 Locules (compartments) with a single ovule in each locule. The 3 Styles are usually bent backwards. The rest of the flowers on the spike are male. In Male flowers, there are many Stamens, which are inserted on a usually hairy Receptacle (is that expanded tip of the flower stalk from which the floral parts develop. It is greatly expanded in the Asteraceae and Ficus). Filaments are inflexed in bud but become erect when the flower opens. There is no ovary present. Pollination is by bees. (Sep-Nov).
The smallish 3-lobed Fruit is a Capsule (a dry fruit resulting from the maturing of a compound ovary which usually opens at maturity by one or more lines of dehiscence) with 3 persistent Stigmas and is about 1cm long. It is yellow to brown and hairy when mature. Seeds may have a caruncle (a fleshy structure attached to the seed). (Sep-Nov). In (May-Jun) the dried out capsule dehisces (opens: – discharging seeds in this case).
Distribution & Ecology
The plant commonly occurs on stony and quartzite (rock composed almost entirely of quartz. It is non-foliated and usually forms from the metamorphism of sandstone) hills. It is the dominant tree on the rocky western facing mountain slopes of NW Cape e.g. near the Langeberg. Also found in Northern Cape; KwaZulu-Natal; Gauteng; and round Magaliesberg, in Limpopo, Mpumalanga, North West, Northern Cape. Outside the RSA it is found in Swaziland, Namibia and into tropical Africa – including Malawi, Nigeria and Sudan. The Crested Guineafowl, Emerald-spotted Wood Doves, Tambourine Doves, Terrestrial Bulbuls Francolins and others, eat the Fruit. Butterfly larvae, with large green bodies and horny heads, are the Green-veined Charaxes (Charaxes candiope) feed on the Leaves.
This is a good garden tree. The Wood is pale, dense, hard, yellow, termite and resistant and is used for roofing poles, hut poles and fencing. The Leaves may be poisonous but are browsed by game and stock. Bushmen girls use dried, powdered leaves as perfume. The tree is relatively quick growing. Antioxidants from the plant have been found to have a beneficial effect in the management of cardiovascular, inflammatory, malignant and neurodegenerative among other diseases. The geographic location of the plants seems to profoundly affect the concentrations of active ingredients in the extracts of this plant. The bark of Croton gratissimus yielded four cembranolides, including the first reported example of a 2,12-cyclocembranolide. This compound showed moderate activity against the PEO1 and PEO1TaxR ovarian cancer cell lines.
Boon, R. 2010. Pooley’s Trees of eastern South Africa. Flora and Fauna Publications Trust, Durban.
Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.
Lawrence, G. H. M, 1951. Taxonomy of Vascular Plants, The Macmillan Company, New York. Tenth Printing 1965.
Palmer, E. & Pitman, N. 1972. Trees of southern Africa, Balkema, Amsterdam, Cape Town.
Schmidt, S. Lotter, M. & McCleland, W. 2002. Trees and Shrubs of Mpumalanga and the Kruger National Park.
van Wyk, B. & van Wyk, P. 1997 Field guide to Trees of Southern Africa, Struik, Cape Town.