Wednesday, 12 July 2017

In flower: Pelargonium reniforme

P.reniforme flower
 Just come into flower in my conservatory is a new plant of Pelargonium reniforme, the kidney-leaved pelargonium. This species originates from the Eastern Cape province in South Africa, where it grows on dry flats which are subject to fairly regular fires. It is a small plant, growing as a shrub around 30cm tall, sometimes to 1m. The leaves are kidney-shaped (hence the name) and are covered with downy hairs which help reduce evaporation.

P.reniforme whole plant
During the dry season as with many South African plants they lose their leaves, bursting into leaf after rain. If a fire sweeps through the area the plants still survive by means of their tuberous roots, which store food for the plant when it cannot photosynthesize. Although these roots are a good means of survival, even below ground the plants are not entirely safe from predation, as the same habitat is occupied by various species of mole-rat, specialised rodents which feed on the underground storage organs of savannah plants. As a deterrent the plants storage various bad-tasting compounds in their roots against rodents and probably insects as well – many beetles for example have grubs which feed on plant roots.
Damaraland mole-rat
A very long time ago people discovered that the deterrent compounds have medicinal properties, and although the plants are not threatened they are collected for use in local herbal medicines. They are also grown commercially, and are a component of herbal medicines for sale in Europe.
The attractive pink flowers attract day-flying insects, and are apparently visited by many species from butterflies to flies and long-tongued bees. The seeds have long awns which curl in response to changes in humidity, drilling the seed into the soil.

In cultivation they are easily propagated from cuttings or seed. In dry climates they are apparently frost-hardy, but in the UK they would need to be brought in for the winter.

(mole-rat image from Wikipedia, other photos mine)

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