Karura Forest #22: Muiri Trail
The cache, a black-taped, push-topped, tablet tube micro, is hidden in a stump on this trail which runs north-south through the middle western part of the forest between Junction 27 near the Karura Falls to Junction 44 to the east of Lily Lake.
For background information on Karura Forest including access, fees, opening times, features, a detailed trail map and useful links, see GC4PD3V Karura Forest #1: Intro, Info & Entry.
Muiri is the Kikuyu name for Prunus (or Pygeum) Africanus (Red Stinkwood or Bitter Almond), an evergreen tree 10-25m tall found in montane regions of sub-Saharan Africa and the islands of Madagascar, Sao Tome, Fernando Po and Grande Comore at 900–3400m asl. It had a high light requirement and grows best in forest gaps. It has black-brown, corrugated or fissured, and scaly, bark with a characteristic rectangular pattern.
Like other Prunus species, it has extrafloral nectaries that provide food for antiherbivore insects in return for protecting foliage.
Insects pollinate the tree and the very bitter fruit is relished by birds and animals, which spread the seeds.
Tree parts are traditionally used medicinally for fevers, malaria, wound dressing, arrow poison, stomach pain, purgative, kidney disease, appetite stimulant, gonorrhoea, and insanity (!). Since this indigenous knowledge was ‘discovered’ by western medicine in the 1970s, its bark has been heavily exploited all over Africa for western markets because a bark extract, pygeum has been clinically proven to reduce Benign Prostate Hyperplasia (swelling of the prostate gland) in ageing men, reducing the need for expensive and potentially life-threatening surgery. It has also shown promising results in the treatment prostate cancer. Prunus africana is the only African variety of more than 200 species of Prunus around the world used by pharmaceutical companies to manufacture medicines used to treat prostrate problems.
Kenyan international trade in medicinal plants is dominated by Prunus africana exports to France (800 tonnes exported between 1990-1995 and 300 tonnes in 1996). In 2011 the bark was worth $220/tonne. Global trade is estimated to be worth $220 million/year and demand is expected to increase as developed country populations age and the incidence of prostatic cancer rises.
Collection of mature bark for this and other medical uses has resulted in the species becoming endangered as it continues to be taken from the wild. Sustainable bark harvesting is possible by removing strips of trunk bark which grows back within 2 years rather than girdling (and killing) the trees. Prunus can live for up to 80 years and if a tree is well looked after, it can be debarked six to seven times in its life time. However, high prices for the bark lead to some harvesters removing too much of the bark in an unsustainable manner. See here for an interesting 2009 article on the over-exploitation of the tree in Kenya which has led to the risk of its extinction and a temporary government ban on exports in 2002. The ever-growing demand for and value of the bark has since
led to the cultivation of the tree for its medicinal uses. See here for an article on Prunus Africanus trade and economics and here for a fascinating article on the tree's genetic heritage.
The timber is a hardwood used to make axe and hoe handles, utensils, wagons, floors, chopping blocks, carving, bridge decks, and furniture. The wood is tough, heavy, straight-grained, and pink, with a pungent bitter-almond smell when first cut, turning mahogony and odourless later.
Other uses include: erosion control, windbreak, soil improver (leaves can be used as mulch and green manure), and for ornamental purposes - as an attractive garden shade tree.
See here for more information on this most useful and highly valuable tree.