Wednesday, September 30, 2015

The Curious Case of the Shrinking Violet

by Bruce McDonald

Vaguely familiar? You know how it is, you see something that rings a bell but you can't quite put a finger on it. In amongst the dunes between Rhossili and Broughton beaches on Gower were some low patches of a plant shown in the photo. Some individual plants, some clumps with trailing stems. Not much to go on so take a photo and consult the books. Nothing obvious in the books so have a look at the photos. A few pieces (small - just 2 millimetres) of something withered and rust-coloured. Close-up on these - just shrivelled, well, could be anything. Hang on - alongside these a flower! Tiny - I could not even see them when looking at the plants in the dunes. Quite distinctive but odd. Back to the books - nothing.

Call in the experts. A quick response from Julian Woodman - some sort of Violet. Of course; no wonder the leaves were familiar. Also a little way back along the flower stem a couple of very small bracteoles - another Viola clue. More research - possibly a hybrid? There are tables of hybrids on the Wildflowerfinder website. But nothing really fits the bill. And the odd puzzle - if they were hybrids would one not expect to see some parent plants around? Find an Oxlip (the hybrid) and you are bound to see some Primroses and Cowslips in the vicinity. But here - nothing. The only Violas were Wild Pansies and they bore few resemblances to our specimens. So, back to the dunes for some further observations.

Another observation. On one plant a seed pod - suggests viability.

A rough count. About 30 plants in an area of 20 square metres - they seem to be prospering. Another look at the stems - runners! But are they rooting?

Take a small plant and tease it out of the sand - possible rhizome?

All the plants seem to be like this - are they all connected? Short of digging up a couple of sand dunes we will not know.

Hmmm! Where now? More Google delving and then, Eureka! A website image of a flower looking very similar to ours and the magic word 'Cleistogamous'. Wikipedia is on hand to clarify - 'Cleistogamy or automatic self-pollination describes the trait of certain plants to propagate by using non-opening self-pollinating flowers. Especially well known in peanuts, peas and beans this behavior is most widespread in the grass family. However, the largest genus of cleistogamous plants is actually Viola' - voila! The opposite is Chasmogamy with open flowers, nectar and pollen but this is relatively expensive in terms of energy.

Wiki goes on to comment that Cleistogamy often occurs in unfavourable sites or adverse conditions. Heavy grazing by livestock or deer or shortage of light may bring on a bout of self-pollination. So the probability is that these violets have become Cleistogamous  because they are growing in nutrient-poor sand-dunes.

Where next? Take a specimen and grow it on in a more nutritious loam - if 'normal' violets appear that will tend to support the argument as well as helping to clarify which variety this is. Also check earlier in the year to see if they do produce conventional flowers in the dunes before reverting to Cleistogamy late Summer. 

Text and Photos by Bruce McDonald

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