Africa's Indigenous Trees - 2 -
You know, its a funny thing, you can spend your entire life walking in the bush and suddenly something catches your eye and starts to make complete sense, and for me seeing the seasonal changes in the bush is always a most interesting time. Nothing ever stays the same, but in nature there is a time and a season, and, as I walk and observe, I witness that change. This year, as in other years, I noted a specific tree coming into full bloom and literally dominating the bush. The spectacular floral display of the knobthorn forming white “fuffy spikes about 10 cm long, between August to November”. In the arid zones away from the river there is not even a leaf on a tree, so seeing the flowers of the knobthorn just catches your eye over the landscape, as one traverses on foot.
Knobthorn – Acacia nigrescens
Commonly found throughout Southern Sub region of Africa they grow prolifically, “in mixed marginal floodplain woodland”. The younger trees are easily identified with their “conspicuous knobs on the trunk and branches of the tree”. I have noted over a period of time that the knobs vanish as the tree matures.
Some Interesting Points
These lovely trees average height of 18 m, can attain a height of up to 25m. “Recent C14 radio carbon-dating aged a specieman with a stem of 43cm as being 313 years old”, isn’t that just incredible… better go round the bush with a tape measure ha ha!
However, according “Trees of the Okavango”, “another specimen of 53 cm measured only 76 years old (Vogel, Fulls and Visser, personal communication).” Clearly size is not a guideline for establishing tree age, “climatic and soil conditions are the major determining factors in this respect”!
On my daily walks in the bush I always stop, listen and watch what is going on around the tree. An there is always an array of wildlife visiting the various knobthorn trees, including red collared barbets, black headed oriels, bees, owls, eagles, tree squirrels, kudu,and giraffe, to name a few. The Knobthorn is certainly a favourite with the Giraffe “forming 40% of their diet, and rather interestingly are believed to be mammal pollinator of this specific tree”.
Tree Value & Use
* Hard wood – was used to make “railway sleepers, mine props in the early days”
* Fertilizer – Being of the acacia family, their root nodules have “nitrogen-fixing bacteria which convert nitrogen back into the soil”
* Medicine – The knobs on the tree are ground down and it is believed to assist with “pain relief for eye infections,to breast enhancement and aphrodisiacs”
Walk & Paint Africa
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‘The Shell Field Guide Series PArt 1 Trees & Shrubs of the Okavango Delta, Medicinal and Nutritional value” by Veronica Roodt
“Game Ranger In Your Backpack”, by Megan Emmett and Sean Pattrick.
“Mana Pools” By Jan Teede
Photos: Julie A M Edwards copyright 2020