Fasciation is a strange name for an absolutely bizarre phenomenon. I’d never seen or heard about it till about this time last year; but now, after two encounters with it, I’m wondering whether it’s just been ignorance that’s kept me from clocking it more often. Never heard of fasciation? Let me explain.
First, look at this purple toadflax. Soft, delicate, lovely. A long raceme of flowers topping a stem ringed by narrow pointed leaves.
Now- look at this.
Look at it! Look at this absolute unit of the plant world. Believe it or not, exhibits A and B are exactly the same species- the difference is that the second plant is fasciated. Fasciation happens when the growing tip of a plant (the apical meristem in botany jargon) stops growing cylindrically but becomes flattened and elongated (the term comes from the Latin word fascis, meaning ‘bundle’). In this case, the fasciation has occurred in the stem (it can also happen in the flowers themselves)- it still shoots off leaves, but the stem itself is so wide that it forms this weird sort of vertical grass meadow. And though it looks so top-heavy that it should be toppling over, that stem is remarkably strong- it easily keeps the plant upright.
Although it’s rare overall, fasciation is something that a wide variety of plants are susceptible to. Nobody seems to be completely sure what causes it, but there seems to be some consensus around there being an underlying hormonal imbalance, itself caused by viruses, bacteria, frost or just random genetic mutation. The most impressive instances I’ve ever seen of it was in viper’s bugloss, where the fasciated stem was as wide as my outstretched hand and there were a good 30-40 flowers bursting from the top (you can see it below, with a non-fasciated stem for comparison). It was by far the most impressive thing we saw that day- and for a zoologist to be saying that, you know it has to have been very impressive indeed. I’ve been planning to do more botanising with my summer this year- if only these summer downpours we’ve been having would like to take a break…
