Saturday, December 12, 2009

African Pedaliaceae

I think plant enthusiasts tend to be drawn to particular kinds of plants over time, as their obsession deepens and they gain experience growing a wider array of plants. I've always liked plants in the Pedaliaceae, they usually have very nice flowers and unusually interesting seed pods, typically winged and/or with spines or hooks, sometimes quite savage spines or hooks. The orange flower is Pterodiscus aurantiacus, a small caudiform which grows in summer and needs to be dry in winter, when the leaves are shed. I've seen its cousin P. speciosus in habitat in Gaborone, Botswana. It has much larger purplish flowers and the caudex is buried in the ground, with only annual stems emerging during the rainy season. Pterodiscus are easy to grow, they like warmth and good light during their summer growing season, and dry conditions during their winter dormancy. Occasionally plants may fall victim to rots, but they set seed fairly easily, which can thus serve as a backup in case a plant is lost.
Dicerocaryum eriocarpum is a low growing creeping plant from the summer rainfall areas of South Africa and nearby nations. It makes flat seedpods with a couple of sharp spines projecting out, the better to embed itself within some hapless animals foot (or human shoe) to ensure that its seeds are dispersed far and wide. It is a nightmare to extract the individual seeds from the pods without crushing them, but if done successfully it is not hard to germinate and grow. Alternatively the entire pod can be sown and when it breaks down the seeds will eventually sprout. Like Pterodiscus it relishes warm sunny weather, but I find it hard to keep happy in winter--lthus far letting it go completely dormant results in a dead plant, so it appears best to bring it inside, keep it under lights or in a sunny spot, and water just enough to keep it alive. Pest control may also be necessary, white flies and spider mites are fond of it when it is indoors. The flowers are borne all summer, and it appears that more than one clone is needed to set seed, though I have not grown it long enough to definitively verify this. If the pods or plant is wet, it exudes a strange muciligenous substance, which probably aids in trapping/suffocating insect pests and making it less palatable to larger herbivores.

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