Palms and the Zambezi Valley
Palms and the Zambezi Valley
The answer to the question “when is a tree not a tree?” could be: when it’s a palm. In fact I understand that in “palm circles” it is definitely not done to refer to palm ‘’trees”! However, many palms do fit most definitions of a “tree” for instance ‘a big plant with a stick in the middle’ or ‘if you can sit in its shade (and many people add ‘and have a cup of tea’) it must be a tree’. There certainly are differences between palms and trees the main one being that most trees classed as dicotyledons have the ability to expand their trunks in proportion to their height. The xylem, the water transporting vessels, increase in number each growing season forming rings in the wood. Palms are monocotyledons having the xylem and phloem in what are known as vascular bundles, which are not able to increase in size. Palms cannot start growing upwards until the stem is wide enough to support itself and the limited number of leaves it bears.
Although usually evocative of sandy beaches and tropical islands there are indigenous palms in the land locked countries of Zambia and Zimbabwe and they are associated with the Zambezi Valley in one section or another. They are a relic of a period when the land was much wetter and probably and a lot more tropical than it is today.
The leaves of palms are either pinnate (like a feather) or palmate (like a hand or a fan). The palm best known around the Victoria Falls/ Livingstone area with pinnate leaves is the Wild Date Palm, Phoenix reclinata, and as the name suggests, reclining or leaning over, as it does, so gracefully, adding to the ambiance of the river above the Victoria Falls. The fruits of the Wild Date Palm are ovoid, about 1 to 1,5 cm long, thinly fleshy and not at all like those of the well-known date palm, Phoenix dactylifera, which has been cultivated by the nomadic peoples in Arabia and north Africa since 4000 BC.
The pinnate leaves have the lowermost leaflets modified to form spines. The margins of the upper leaflets fold upwards so that they form valleys on top. This is unusual for pinnate-leaved palms, as the leaflets usually fold downwards so that they form a roof on top, as do those of the Raphia Palms, Raphia farinifera which, with leaves up to 18m long, have the largest leaf in the plant kingdom. These are found along the lower reaches of the Zambezi and some of the tributaries and I have seen it on the Liuwa Plains. In the mid-Zambezi Valley are the Vegetable-Ivory Palms, Hyphaene petersiana, one of the fan-leaved palms. Around the Kariba shores and along the Zambezi River towards Chirundu on the Zimbabwe side, there are either very tall ones or those which have not got off the ground, but no intermediates probably as result of animal pressure. During the dry season when there is nothing else to eat I am sure that the growing tip of the Vegetable-Ivory Palms provides a succulent meal. Among the trees drowned by the waters of Lake Kariba the trunks of the Vegetable- Ivory Palm are still standing. One does not think of them as being very hard or very durable, but they obviously are. Like many palms these have separate male and female plants and when flowering and fruiting, it is easy to distinguish between the sexes. The female the Ilala Palm are pear-shaped and those of the Vegetable- Ivory Palm are round. The fruits develop a hard shell with a very hard white centre hence the name vegetable-ivory. I was once told by a tourist that they had been warned not to buy small ivory objects as they might be just vegetable ivory and not the genuine ivory. And this was after the ivory ban. There is the belief that the fruit has to pass through an elephant before it will germinate. Elephants only digest about 40% of what they eat and the food takes about 24 hours to pass through this inefficient digestive system which I do not believe will have any effect on the hard outside case of the Vegetable-Ivory fruit at all. In 24 hours an elephant can walk quite a long way and when the fruit is deposited it is accompanied by an ideal germinating and growing medium. So it is not surprising that Vegetable- Ivory Palms grow along old elephant routes.
When the sap is rising, if these palms are tapped near the growing tip they yield a palatable liquid. If the tapping is done carelessly and the growing tip destroyed, the palm dies and many have. During an expedition to the Zambezi delta in May 2004 I bartered a tin of bullybeef and a box of matches for a newly picked green coconut and by sign language managed to have it opened. There had been a misunderstanding about who was taking the water so it was at a bit of a premium. That coconut milk was like pure nectar. This is proof that coconut palms Cocos nucifera grow in the delta and I know of one at Tashinga but I am sure that one was planted.
Read more about the region in our destination guide:
Kariba & Middle Zambezi
Read more articles from this issue:
Zambezi Traveller (Issue 07, Dec 2011)
More from the Zambezi Traveller:
Know your trees