Sex and violets

These dog violets are all over the place just now, and so-called because unlike sweet violets they have no scent. Even so, they are very effective at getting fertilized.

The flowers have 5 petals, the two on top acting as flags that signal to passing insects (flies and bees). The bottom petal provides a sort of landing strip with guidelines that lead the insect towards the source of nectar. To reach it, the insect has to push its head through a fuzzy portal, rather like the brushes of a car wash, formed by the hairs at base of the two lateral petals. Meanwhile pollen grains drop from the overhead anthers onto the back of the nectar seeker.

This all seems very efficiently evolved but the violet employs a sort of belt-and-braces system of reproduction in case insect pollination doesn't work, for example in a cold spring. In addition to its colourful flowers it produces, at the end of the season, tiny, colourless, rudimentary 'flowers' which are self-pollinating. They are very economical of the plant's resources since they do not require the production of petals, nectar or pollen, in fact the name for this trait is cleistogamy meaning closed marriage (kind of like staying in with a turkey baster instead of shelling out on make-up and high heels to go out on the town...)

If you think that's enough reproductive strategy for one little flower, you'd be wrong. When the seeds are formed, whether as a result of open or closed marriage, they come with a peculiar feature. Each one has an edible appendage, called an elaiosome, which is rich in oil and nutrients - and irresistible to ants. The ants drag the seeds away, down into their underground nests where they nibble away the yummy bits and discard the rest of the seeds which are then well placed to germinate in the soil. The process is known as myrmecochory, ant dispersal or ant farming.

So, next time you see a violet remember it's not just a pretty face.

The modest, lowly violet in leaves of tender green is set; so rich she cannot hide from view, but covers all the bank with blue. Dora Read Goodale