Yellow rattle (Rhinanthus minor) is also known as hay rattle. It is common on grassland and downland from May until August and has a preference for chalk soils. It is a major contributor the wonderful flower meadows at Durslton in mid-summer where it is exceedingly common but it also common elsewhere in the county too.
Yellow rattle flowers look very much like a nettle but they are not related at all. It is a member of the figwort family, closely related to the parasitic broomrapes, and is semi-parasitic on grasses. It is considered an excellent way of minimising the impact of grass in meadows making it popular with ecologists and conservationists as it adds to the general biodiversity of any meadow it grows in. With this in mind it has been sewn for that very purpose.
When the seed cases ripen the seeds 'rattle' inside the the calyx, hence the common name. The scientific name Rhinanthus minor begs the question "is there a Rhinanthus major?" There is, it is the greater yellow rattle but this is very uncommon in Britain and certainly does not occur here in Dorset.Yellow Rattle: the hay rattle