This monocarpic Tree may reach 24m high. The long Leaves are pinnately compound. Flowers are actinomorphic, monoecious, unisexual, in a spadix. Fruit is large. Falling tree disperses the Seeds..
RSA Tree No. 26.
Common names: Kosi Palm, Kosi Raffia-palm, Giant Palm.
Family: Arecaceae, Palmae (Palm family). There are about 180 genera and in excess of 2 500 species in these monocotyledonous plants. The usually unbranched Trunk is covered with persistent leaf bases or with transverse scars. The tree is evergreen and mature Leaves are pinnately or palmately compound. They occur at the apex of the trunk. The Petiole or rachis is often armed with prickles. The Flowers are in a spadix (a thick fleshy spike inflorescence) surrounded by a spathe (a leaf-like curved bract). They are small and usually unisexual with male flowers in the upper part of the spadix. The 3 sepals and 3 petals are free or fused below. Male flowers usually have 6 stamens. Female flowers may have staminodes present and are usually 3-locular with 1 ovule in each. Fruit is a berry or a drupe with up to 3 seeds. In southern Africa, there are 5 genera and 6 species. Genera include Jubaeopsis, Phoenix, and Raphia.
Name derivation: Raphia a needle – possibly referring to the sharply pointed fruit. australis – southern. There is 1 species of the genus Raphia southern Africa.
Conservation Status: V R (Vulnerable). 2009. Population is characterised by an acute restriction in its area of occupancy (typically less than 100 km2). Individuals only reach maturity after 25-35 years at which point they flower and die. It is protected in the Kosi Bay section of the Greater St. Lucia Wetland Nature Reserve.
The usually solitary and occasionally suckering Tree may reach 24m high but usually about 16m high. The Stem is distinct and covered in old leaf bases. In the angles of the lowest of these, many small rootlets cover the bottom of the stem. The tree has pneumatophores (breathing roots to cope with being water logged).
The very large linear Leaves are pinnately compound (leaflets arranged along either side of the leaf rachis – central stalk, like a feather). Here the lower leaflets are not reduced to spines. This plant has one of the longest leaves of any plant – up to 10m long. The leaflet Margins have spines which are fine and reddish. The Rachis (main axis bearing flowers or leaflets) has small ascending spines and the Petiole (leaf base) is unarmed. Leaves are dark green to bluish green. There are hooked ascending spines on the Midrib (the main rib of a leaf or leaf-like part, a continuation of the petiole) of leaflets.
The small Flowers are borne on a Spadix (a thick or fleshy spike inflorescence) surrounded by a Spathe (a leaf-like, curved bract). The spadix is, impressively, up to 3m long and the Peduncle (stalk of a flower cluster) is covered by imbricate (having regularly arranged, overlapping edges) of bracts. Flowers are actinomorphic (regular, symmetrical. The Perianth – the calyx and corolla are divisible into 3 or more identical sectors or mirror images), monoecious (separate male and female flowers on the same tree) and the tree is monocarpic (the plants flowers once, set seeds and then die). After about 25 years the upright, brown branched inflorescence grows up above the crown of leaves reaching an impressive 3m in length. Flowers have a tubular Calyx and Petals. They are 2-ranked with the Male Flowers above the female flowers and have 2 prominent longitudinal ridges on the bracteoles (secondary bracts). Here the Calyx is tubular. There are 3 Petals in the Corolla. There are 6-16 Stamens and there is no ovary. In the Female Flowers, there are an outer and an inner bracteole. They have a calyx and corolla that are accrescent (increasing in size with age). Stamens are absent but there is a ring of Staminodes (sterile stamens) attached to the corolla. The ovoid, 3-chambered, superior Ovary is present and contains a single Ovule. From this, if present, is a short Style ending in 3 Stigmas.
The Fruit takes about 2 years to mature and is covered with a shiny, overlapping chest of brown scales that are arranged in vertical rows. Each fruit is up to 9 x 5cm. The fruit is beaked and a thin layer of orange flesh covers the single “ivory” seed. The fruit is scattered when the tree falls. The completely mature inflorescence can have an amazing mass of up to 250kg! Each fruit has 1 seed. After flowering the tree dies. The Seeds germinate easily.
Distribution & Ecology
Location: NE KwaZulu-Natal and SE Mozambique. Found in Swamp forest around Kosi lakes near Lake Amanzimnyama – one of 4 interconnected lakes which are the preferred habitat of the Palmnut vulture or vulture fish-eagle (Gypohierax angolensis), which nest in the palms and feed on the thin layer of orange flesh of the Raphia fruits. They also feed on crabs, snails, locusts and fish. In this area, the tree may be found on seasonal inundated coastal dunes. The tree also occurs in Gorongosa National Park in Mozambique. Egyptian fruit bats (Rousettus aegyptiacus) roost in the crown. The butterfly larvae of the Palm-tree night fighter (Zophopetes dysmephila) feed on the leaflets.
The Leaves are the source of raffia, which is used for hut building. The giant petioles (leaf stalks) are of low density and suitable for raft building. Seeds are quick to germinate and do best with lots of water and a low wind environment.
Boon, R. 2010. Pooley’s Trees of eastern South Africa. Flora and Fauna Publications Trust, Durban.
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Ginn, P.J. McIlleron, W.G. Milstein, S. 1989. The Complete Book of Southern African Birds. Struik Publishers (PTY) LTD. Third impression 1991.
Lawrence, G. H. M, 1951. Taxonomy of Vascular Plants, The Macmillan Company, New York. Tenth Printing 1965.
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van Wyk, B. & van Wyk, P. 1997 Field guide to Trees of Southern Africa, Struik, Cape Town.