Yellow Rattle

We found this strange looking plant in a meadow in Perthshire. The old, brown seed heads from last year look like and sound like ... rattles.

I have discovered that Yellow Rattle is a useful plant to introduce when creating a wild flower meadow, because it is semi-parasitic on the roots of plants, especially grasses, and once established will reduce the vigour of the original grass by up to 50%. It fixes its roots onto the root system of an adjoining grass, extracting water and minerals from it. All ancient meadows have Yellow Rattle.

Thanks to The Wildflower Shop for the information.