I meant to post this with the other yellow flowers at the end of May but somehow it got missed. However, although I really ought to be posting another grass (current area of interest!) this fits in nicely.
It's growing in 'the orchard' where we've been encouraging meadowy plants. In the past a lot of chickens inhabited the area and deposited perhaps more nitrogen than is good for a diverse meadow.
The solution, in part, was to introduce yellow rattle, Rhinanthus minor, which is hemiparasitic on the roots of neighbouring grasses, reducing their vigour. This increases competition and diversity. It took me three years to get them going, last year being the first, and I was anxiously surveying the sward for signs of return this year.
It's a member of the Orobanchaceae or broomrape family which all share some degree of parasitism. Some are wholly parasitical, having no chlorophyll of their own.
The key to propagation once established is to cut the meadow after July once the seeds have set. You then need to 'make hay' by laying the cut vegetation out and turning it as it dries, before removing it.
This year I've tried to get birdsfoot trefoil to grow, apparently without success.