Although begonias have been cultivated in Europe for centuries, it is surprising that some have been introduced relatively recently, and new species are being discovered all the time. I mentioned the introduction of the imposing B. masoniana the other day and today we have another plant, grown mostly for its foliage, that was not introduced until 1979 and named in 1981. The Brazilian Begonia soli-mutata  was discovered by the great landscape designer Roberto Burle Marx from Rio de Janeiro.

I did mention that I would discuss the genus in a bit more detail so, before we launch into an unusual feature of the this plant, something about the flowers. Begonias are monoecious, having separate male and female flowers on the same plant. In fact, the flower clusters usually have both and it is typical for a make flower to have two females behind it in the cluster. Male flowers usually have two, large, outer, almost round petals that create a clam-shell-like bud and two smaller, narrow petals set at 90 degrees inside, creating two pairs. In the centre is a clusters of stamens. The female flowers have four or more, rather narrow petals and in the centre is a cluster of curled stigmas. Behind the petals is a (usually) three-winged ovary that produces masses of tiny seeds. The males are often smaller than the females but in the common, large-flowered tuberous kinds we grow for bedding and containers the males are larger and fully doubled while the females are less attractive.

This species is grown for its leaves though. Begonia soli-mutata name means ‘sun change’ and a common name, if there can be a common name for such a recently introduced plant, is the suntan begonia.

It is called that because the leaves can change colour, depending on the light intensity. It this though that this is because the chloroplasts ( structures that contain the chlorophyl – green pigment – in the leaves) can re-orientate themselves to capture more light in dark situations. In good light the leaves turn light green and in darker conditions they turn dark green and, apparently, this can happen in as little as ten minutes. I have moved my plant around but with poor winter light I have not seen very dramatic changes – when things get better I will try shading half a leaf to see if I can get a change.

Even without this party trick this is a lovely little plant, about 20cm high, with interesting, puckered leaves and covered in red or golden hairs. The photos above and below are of the lower leaf surface showing the hairs.

And here you can see that the raised lumps on the upper surface each have several points and short hairs.

It is another that likes warmth and high humidity to keep it in good order and it has a rhizomatous habit, creeping across the surface of the compost. The foliage is extremely attractive and it is an exciting plant.

Like my other begonias it was from Dibleys* – they do supply mail order in the UK but not in winter because these plants are sensitive to cold.

*http://www.dibleys.com/

begonia soli-mutata, begoniaceae, roberto burle marx