Regenerating over-grazed or poor-condition meadow will increase the biodiversity and create a wide range of habitats for wildlife and wildflowers.
Whilst this may seem counter-intuitive, it is known that, in general high fertility leads to low diversity. The reason for this is that fertile environments will quickly be monopolised by a few strong, ‘bullying’ species that outcompete the others, leaving no room for additional plants. These bullies are often grasses, such as ryegrass, or clovers. In less fertile systems there will be a greater number of necessary plant interactions to extract the vital nutrients from the soil; this leads to complex plant arrangements, a greater number of species and, thus, a greater number of dependant species.
Fertility can be effectively reduced with a regime of mowing and removing the cut grass, or by intensively grazing the field (in which case much of the nutrition is removed with the animal - a relatively small proportion is returned in the form of manure or dung).
The yellow rattle, Rhinanthus minor, is a hemi-parasitic plant that derives some of its nutrition from grass and clover species. The plant can be used to increase biodiversity in meadows as it will parasitise the dominating species (as these offer the greatest quantity of nutrients), creating openings for less-vigorous species to take hold.
Yellow rattle is a herbaceous annual that will grow to between 25 and 50cm tall. The leaves are opposite and serrated like the nettle, the blooms are yellow. The seeds are stored in dry capsules that, when ripe, will rattle, giving rise to the common name of the plant.
To cultivate yellow rattle, such as when regenerating meadows, the seeds are sown in September or early Autumn. The seeds require chilling over winter to germinate and missing this window will result in a failed crop.
If sowing directly onto the meadow, harrow or graze the site to open the soil up to 50%. Grass should be kept short prior to sowing (40 to 50mm) for best results. Graze lightly the first year and wait until the end of July before cutting to ensure the rattle has set its seed.
To sow yellow rattle in seedling trays an overcrop of grass must be used. To prepare such trays, sow with a grass (what type?) and allow this to take hold (how long?). Once the grass has fully established, expose a little bare earth beneath the grass in each module and sow around 5 seeds in each. Trim the grass to a few centimeters high and place the trays outside to stratify.
If necessary, yellow rattle can be removed by mowing between March and July before the plant has set seed. This may be desirable if it appears that the plant is parasitising other, prized species.