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Wednesday, October 2, 2013

Coast Coral Tree (Erythrina caffra)

Family Fabaceae
Ecology
Both birds and flying insects pollinate coastal coral trees. The flowers of Erythrina caffra do not produce any fragrance, and only colour, in combination with the reward of nectar, which the tree produces in abundance, is used to attract pollinators. Birds such as Redwinged starlings (Onychocnathus morio), bulbuls (Pycnonotus sp.), yellow weavers (Ploceus subaureus), sunbirds (Nectarinia sp.), orioles (Orioles sp.), and many others feed on the nectar and red blossoms and can be seen by the hundreds visiting these trees in the early spring. The flowers appear before the leaves and this may well be a strategy for visible advertisement to attract as many nectar-feeding birds as possible. The shape and design of each flower is in such a way that the stamens are exposed and therefore pollen transfer by birds and insects takes place with ease. It is estimated that each flower may hold as many as 7-10 drops of nectar and each flowerhead may hold up to 80 florets.

The red berries are also an important food source to many seed-eating birds. Birds therefore not only pollinate the flowers but also aid in seed dispersal, which ultimately impacts on the natural distribution of the species throughout its entire habitat range. The seeds are also fed on by developing larvae of many winged beetles, which lay their small yellow eggs inside the immature pods. Borers also sometimes attack trees and do considerable damage, particularly to young trees. The dead wood of the coral tree is soft and is an ideal nesting places for birds such as the Pied barbet (Tricholaema leucomelas), and Cardinal woodpecker (Dendropicos fuscescens), while the hollow trunks are often inhabited by swarms of bees.

The branches are armed with prickles, which might serve as protection to herbivores especially when trees are still young. Fully grown trees are fairly drought resistant and can withstand several degrees of frost. In areas where there is severe frost, it may well grow but chances are that they won't flower.

 Description

Erythrina caffra is a medium-sized to large deciduous tree, 9-12 x 7-11 m. Its size depends largely on the climate and soil conditions. This species forms a round-headed, spreading canopy and has a beautifully light green appearance when in leaf. Trees may even reach a height of 20 m in coastal and forested regions where the conditions are optimal. Some of the largest and most beautiful specimens grow in the Addo National Park's Alexandria Forest where, next to the yellowwoods, they are the tallest trees.

The trunk and branches are grey, sometimes set with short, sharp prickles.

As with all other erythrinas, the leaves are typically trifoliate (three leaflets), which are broadly ovate (egg-shaped) to elliptic (oval and narrowed to rounded ends, widest at or about the middle), the terminal leaflet being the largest, 80-160 x 80-180 mm. The lateral leaves are slightly smaller and without hairs or prickles. The leaflet petiole (leaflet stalk) is up to 160 mm long and with or without prickles. The leaves closely resemble those of a sister species, E. lysistemon (sacred coral tree), which is why it was for many years thought to be the same species. When not in flower it can be rather difficult to tell the two species apart.

 Distribution and Habitat

Erythrina caffra is a subtropical tree that occurs in the warm and frost-free to light frost coastal regions of the Eastern Cape and northern KwaZulu-Natal. The trees are found in various soil types from wet, well-drained, humus-rich soils to dry, clayey soils. The distribution from the Humansdorp District to Port Shepstone and inland to about 57 km into the Albany District of the Eastern Cape. Further north it is found in the Hlabisa and Lake Sibayi areas of Zululand where it is over 400 km away from its southern populations. This is quite a surprising distribution range.

 Uses and cultural aspects

In South Africa, Erythrina caffra is seen as a royal tree: it is a much respected and admired tree in the Zulu culture and is believed to have magic properties. Specimens have been planted on the graves of many Zulu chiefs. In parts of the Eastern Cape, local inhabitants will not burn the wood of Erythrina caffra for fear of attracting lightning.

They were also planted as living palisades around the houses of the early settlers, used as fences around kraals and waterholes. In the Peddie District of the Eastern Cape there are a number of these living fences that have been closely planted around waterholes to keep livestock from the water or to channel them to the entrance.
The wood is very soft, spongy and light. Hollowed trunks were used to make canoes and troughs, and cubes of wood were used as floats for fishnets. When tarred, the wood made good roofing shingles. The African women of South Africa make the highly decorative seeds of Erythrina caffra into necklaces. Children also love collecting them where they are known as lucky beans. All coral trees produce a poison with a curar-like, and paralyzing action, which is used medicinally to relax the muscles in treating nervous diseases. The seeds of all erythrinas are said to be poisonous and the leaves of Erythrina caffra are known to have poisoned cattle. The bark of E. caffra is used topically to treat sores, wounds, abscesses and arthritis. Open wounds may be treated with powdered, burnt bark; infusions of the leaves are used as eardrops for earache; and decoctions of the roots are used for sprains. The Vhavenda use the bark for toothache. Erythrina alkaloids are known to be highly toxic, but the traditional uses strongly suggest antibacterial, anti-inflammatory and analgesic effects.
 The wood is very soft, spongy and light. Hollowed trunks were used to make canoes and troughs, and cubes of wood were used as floats for fishnets. When tarred, the wood made good roofing shingles. The African women of South Africa make the highly decorative seeds of Erythrina caffra into necklaces. Children also love collecting them where they are known as lucky beans. All coral trees produce a poison with a curar-like, and paralyzing action, which is used medicinally to relax the muscles in treating nervous diseases. The seeds of all erythrinas are said to be poisonous and the leaves of Erythrina caffra are known to have poisoned cattle. The bark of E. caffra is used topically to treat sores, wounds, abscesses and arthritis. Open wounds may be treated with powdered, burnt bark; infusions of the leaves are used as eardrops for earache; and decoctions of the roots are used for sprains. The Vhavenda use the bark for toothache. Erythrina alkaloids are known to be highly toxic, but the traditional uses strongly suggest antibacterial, anti-inflammatory and analgesic effects.
More common are the uses as a garden plant. These trees are admirably suited for park planting or used as a tree to line streets of cities, small towns and villages. Fine specimens have been cultivated in Grahamstown and Graaf Reinet. In the Boland town of Worcester, there are beautiful specimens used to line Tulbagh Street in the front section of the town. There is also a delightful avenue of them near Port St. Johns where they are a splendid sight when in full spring flower and alive with birds. On lawns they make beautiful specimens as single subjects but one must be aware that in time these trees may become rather big and bigger gardens ultimately are more suitable.