Yellow Rattle, Rhinanthus minor

Hurrah! I can now make out the Yellow Rattle (Rhinanthus minor) seedlings in our meadow areas here. Rattle is particularly important for us as our soil, though unimproved, is pretty good, and without it the grasses would run amock and crowd out any perennial wildflowers. We're lucky though in that we don't have too many bullies like cocksfoot or ryegrass, which would be a struggle for it, and consequently I was amazed at the pretty much instantaneous effect it had when we introduced it.
As a non-botanist, Yellow Rattle seems as odd as it is helpful. Rattle is semi-parasitic - it attaches itself to the roots of grasses in particular - and the reduction in vigour of the surrounding plants is marked. It must have been a plague for farmers in the past, but for establishing and managing diverse meadows it's really helpful. Rattle seeds need to be cold over a prolonged period ("stratification") before they can germinate, so you can only sow them in autumn - unless you find someone who has kept a supply in a chiller over the winter. The seedlings start to grow early in order to get as much light as possible before the surrounding grass starts to get going, but when they get to a certain point will conk out unless they can find plants nearby. Bumblebees in particular like its rather beautiful flowers, which appear in June. It sets seed promptly, which explains its other common name, Hay Rattle; traditionally, once you heard its rattle it was time to take a hay cut. As it's an annual and the seed isn't viable for long, if you mow in late June for a couple of years it will disappear. I'm still understanding how best to establish Yellow Rattle populations, which is a bit hit and miss. The best solution seems to be to wait for a season after sowing a meadow mixture and then sowing it seperately, when there are enough plants around for it to parasitize but not so many to crowd it out. We're currently running a trial on a mixture with a lot of Rhinanthus in it which was all sown last autumn, and it's looking a bit dodgy... Anyway, you'll find a lot more rattle about Yellow Rattle in our main website.