Four miles per hour is too slow – the plants are pushed down. Eight is too fast – tearing stalks right off. My dad is carefully driving a large yellow digger, more commonly seen piling up the muck heap, through a wildflower meadow. Its bucket is low to the ground, as it moves at precisely 6mph. This is the innovative technique Dad has developed for harvesting an unusual crop.

Just a few minutes later, the digger bucket contains lots of dry husks and the brownish seed of a plant called yellow rattle. This wildflower grows up to 50cm high and has yellow, tubular flowers that emerge from the large protective calyx, or seed pod. When the calyx dries out, the seeds within make a rattling noise as you walk through the meadow. That sound was the traditional sign that the grass was ready to be cut for hay.

Back in the barn, the seeds are sieved from their husks and other debris by hand, in a process that looks rather like panning for gold before they are weighed and packaged. Nature’s gold, yellow rattle is described by Plantlife as “the single most important plant you need to establish when creating a wildflower meadow”. Quite an accolade for such an unremarkable looking plant.

Known as the meadow maker, yellow rattle grows in an unusual way. It is semi-parasitic – and therein lies its benefit. While it does photosynthesise and use its roots, it also latches on to the root systems of other plants, mainly grasses, and extracts nutrients and water from them. This stunts the growth of usually dominant grasses and allows the space for a vast range of wildflowers to thrive.

By harvesting some of the seeds in this well-populated field, they can be spread round the farm to improve more of the meadows, as well as generate a small side income from selling the seeds online. Since Monty Don, on BBC Gardeners’ World, told everyone to plant yellow rattle, there has been a lot of interest. As each small package whizzes off in the post, it’s gratifying to know that our yellow rattle will be meadow-making around the country.