Time to play ‘guess the odd one out’ of the above photos, taken along the same 10 metres of roadside verge……(clue: you can move the cursor over the images). The answer? They’re all from the family Leguminosae with the characteristic upright standard petal at the back, and a ‘keel’ projecting forward, like garden peas and beans. But the odd one out is the first one, Psoralea bituminosa, a plant which looks like clover or lucerne but isn’t. The other two are the same species, Medicago sativa or lucerne (often called alfalfa in the UK), though the yellow flower is a subspecies (falcata). I had to do some close looking and reading to be sure – more disambiguation! I’ll explain.
Psoralea bituminosa has a leaf divided into three, like the others, but the leaflets are elongated, and the flower stalks much longer than for the Medicago. It is supposed to smell of tar, due to glands on the leaf which appear as bright points against the light – I couldn’t see these or smell the tar, hence my hesitation in identifying it. Maybe we have a different variety here, maybe the smell develops later.
The lucerne was easier to identify in the end, because we’ve seen whole fields of it lately, and the plants I saw were escapees from an earlier planting, now naturalised. The flowers are very variable in colour, from deep purple through to light blue, and often have the yellow plants mixed in since the seeds sown for lucerne crops are themselves mixed, and the two varieties interbreed. In fact the yellow is probably nearer to the parent stock, first cultivated in the near East (Iran and Turkey) over 2000 years ago, but grown in Europe since the 4th century CE.
A plant with three names: Medicago and sometimes Medick in English because early Roman writers attributed the plant to the nation of the Medes, in present-day Iran. Alfalfa because the Spanish took the plant and its name alfalfez (from the Arabic al -fisfisa) to South America, and North American settlers took the seeds and name from there, especially from Chile. And to me the most interesting name of all is lucerne: not, as I thought, related to a Swiss town, but coming from the Provencal or Occitan word la lusèrna, meaning meaning a little light, or glow-worm. In fact I think the latter is more likely because the seeds are not only shiny but coiled like a worm.
Lucerne is an amazing plant. Its roots can be up to 15 metres long, and go up to 2 metres deep, giving it great drought-resistance. It flowers in July when other flowers are fading and so is very important for bees. It fixes atmospheric nitrogen like many legumes, so does well on poor soils. It can be cut up to 12 times a year and regrows from its extensive roots – that’s why it does so well on roadside verges which are cut back. It is the most widely grown forage crop in the world. It produces an autotoxin – a chemical which inhibits the germination of rival plants. I could go on, but you have Google and wikipedia just like I do, and it’s time for music.
This is Dinah Washington’s version of the Bessie Smith classic, Back Water Blues. A more rootsy blues for a rootsy blue flower.