Tree may reach 25m. Simple Leaves have translucent dots. Bisexual Flowers are spectacular and 5-merous with 5 impressive staminodes. Fruit is a woody, capsule. The low density Seeds are large.
RSA Tree No. 256.
Common names: Cape-chestnut, Kastaiingboom. The Cape-chestnut only resembles the flowers and fruit of the Horse Chestnut (Castanea species: family Fagaceae) but is not related to it.
Family: Rutaceae. (Citrus family) has 160 genera and 2 000+ species. Leaves often have pellucid (clear, almost transparent in transmitted light) oil glands which are responsible for the aromatic smell. These gland dotted leaves are usually opposite but lack stipules. The regular Flowers are bractless, bisexual or unisexual and usually monoecious. They have 4-5 Petals, which are usually free. The Stamens have anthers that are dorsifixed and 2-thecous (have 2 pollen sacs). Staminodes are often present. The Ovary usually has 5 carpels and the style is simple. Fruit is variable. This family has 23 species in Africa. The Rutaceae in southern Africa are largely concentrated in the Western Cape. Indigenous genera with trees include Calodendron, Ptaeroxylon, Vepris and Zanthoxylum.
Name derivation: Calodendrum – beautiful tree – referring to the flowers. capense – of the Cape. This is the only indigenous species in southern Africa.
Conservation Status: L C (Least Concern). 2009 (Raimondo et al.).
In the forest (photo 186) this Tree may reach 25m high but shorter and more spreading in areas where there is less competition with other trees (photo 970). Bark is grey and smooth even in old trees and often has attached lichen. The Bole (a single unbranched stem, the trunk) may be buttressed in older forest trees. Branches are hairy when young.
This deciduous tree has waxy and shiny Leaves that are comparatively large – up to 22 x 10cm. The tree can be evergreen at the coast but even here it will lose leaves in very cold weather. Leaves are elliptic (oval in outline, having narrowed to rounded ends and being widest near the middle), or oblong (the sides approximately parallel). These simple (has a single blade which may have incisions that are not deep enough to divide the blade into leaflets) leaves turn a golden yellow before falling. The mature leaves are hairless, opposite, shiny and dark green. Crushed leaves have a noticeable citrus aroma. Veins. The midrib (the main rib of a leaf or leaf-like part, a continuation of the petiole) is prominent on both sides. It is yellow above and a greenish yellow below. 20 or more pairs of lateral veins curve upwards together towards the margin. These veins are visible on both sides but are more clearly visible below – as are the net-veins. It is worthwhile holding a leaf against the sun to see the venation clearly. In addition, the many oil glands that are present can be seen as tiny, translucent yellowish dots. Here a hand lens will help (photo 47). The Apex is pointed or tapering to rounded. The Base tapers or may be slightly lobed. Margins are entire and wavy. The Petiole up to 1,2cm long and Stipules (basal appendages of the petiole) are absent.
These beautiful, bisexual and actinomorphic (regular; symmetric) Flowers are arranged in terminal, open Panicles (an inflorescence in which the primary floral axis is branched and these branches may branch again and again – each eventually ending in a flower). Individual flowers are large – up to 6cm and are really striking. Individual flowers are large – up to 6cm. They are really striking. The green, somewhat fleshy 5 Sepals are spread out when mature. They protrude (photo 804) below and between the 5 white or pale pink coloured Petals, which are up to 4 x 0,5cm. The base of each petal is red and becomes purplish further down. Petals curve slightly backwards. There are 5 thin and wide Staminodes situated between and in front of the petals. These distinctive staminodes resemble petals and are pale pink with crimson or purple gland dots. They stand almost upright and separate from the petals and enhance the appearance of the flower. A dome shaped Disc (a more or less fleshy or elevated development of the receptacle) is present. There are also 5 fertile Stamens with long, thin, pinkish Filaments that extend out of the flower. The Anthers are oblong with an immersed apical gland. There is a single Pistil (a unit of the gynoecium composed of the stigma, style and ovary). The superior, 5 locular and 5 lobed Ovary is supported by a gynophore (a stalk within the flower). There are 2 ovules in each locule. The Style is much longer than the ovary. This is a special flower. Unfortunately, the flowers are often high up on a large tree and difficult to really examine. (Oct-Dec).
The large, distinctive brown Fruit is a woody 5-lobed Capsule (a dry fruit resulting from the maturing of a compound ovary, which usually opens at maturity by one or more lines of dehiscence). This capsule is up to 4cm in diameter, with a knobby surface. It dehisces from the base. Large, dark brown to black angled and shiny Seeds are released from the fruit. They are hard but have a low density. The valves (a separable part of a pod; the units or pieces into which the capsule splits, or divides in dehiscing) remain connected to stalk at the apex of the fruit. (Jan-May).
Distribution & Ecology
These Trees are found in the coastal forests in the Western and Eastern Cape as well as inland up to an altitude of 2 000m. Also found up the Eastern part of the RSA (coastal to tropical): KwaZulu-Natal, Limpopo, Mpumalanga, North West as well as Swaziland, Zimbabwe, Tanzania, Kenya, Uganda, Tanzania, Malawi and Ethiopia. Adult trees can withstand temperatures as low as -8⁰C. Butterflies rather than birds visit flowers. Several swallowtail butterflies e.g. the citrus swallowtail or Christmas butterfly (Papilio demodocus) larvae feed on the Leaves and those of other citrus trees, before pupating. Samango monkeys, Rameron and Olive pigeons and Cape parrots consume the Seeds. This Cape parrot, which has a large beak eat these seeds as well as yellowwood seeds. Pollination agents are bees and butterflies.
The Wood is tough and white or light yellow and suitable for making furniture and turning. It is used for planks, furniture, shovel handles and has good bending qualities. Its bending capacity has made it useful for tent bows. The Bark is used to make skin care lotions and may lighten the skin. Seeds are used to make good-luck bracelets. They germinate and transplant well. Yellow Yangu Oil can be extracted from the seeds. It has a high concentration of antioxidants. The seeds are cold pressed to remove the oil from ripe fruit. The oil is used in local skin care and includes UV protection. It also has a high concentration of essential fatty acids and can be used to make soap. Cultivated trees usually grow to less than 10m high at a rate of close to 1m per year. They appreciate moist soil and being frost free when young. The tree may take up to 8 years to flower.
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