Tuesday, 21 August 2018
An instructive clump of Medicago
Yesterday afternoon's visit to the clump of Sickle Medick on Epsom Downs started an interesting online debate. I had posted photographs of the plant(s) on the Surrey Botanical Society Facebook group which elicited responses from several botanists, including Ian Kitching who suggested that the plants could be, in fact, yellow-flowered Sand Lucerne. He then added that there might well be Sickle Medick also present, having had a look through my images of the flowers and fruits. The simple truth is that I had not been a thorough enough botanist, and checking the photographs again it was obvious that a larger plant, with a much different jizz, was present. I needed to go back... and did so this morning, delighted to find both Brian and Linda Pitkin already present. They too had been inspired to get to the bottom of this Medicago conundrum.
The bottom line is that there ARE two sub-species present - both Sickle Medick (M sativa ssp falcata) with yellow flowers and fruits that are nearly straight to curved in an arc - and Sand Lucerne (M sativa ssp varia) with flowers that can appear multi-coloured and fruits that can curve and spiral with 0.5 to 1.5 turns. As Brian mentioned to me, there can be some overlap, although the Epsom Downs plants were straightforward once you got your eye in. The varia was a larger, more straggly plant, with the falcata more ground-hugging, although whether this is a reliable feature I do not know. The images above clearly show that the same plant can exhibit different coloured flowers, with deep purple, yellow and green petals all on show. Yesterday's post showed this species (varia) old, dried fruits, and below are some fresher examples. And yesterday's images of the fresh fruits of falcata can now be joined by drier, older examples (bottom)
It has been an interesting exercise. I now feel a lot more confident with being able to differentiate between these sub-species, and it is pleasing to know that all three - the other being Lucerne (M sativa ssp sativa) - can be found on Epsom Downs.