It is essential to scarify the ground first in order to open up patches of soil into which the seed can be sown. The grass should be ripped out and at the same time remove any dead grass or any unwanted plants.
Poppies & Cornflowers
This is easy to do with grass which has not been very long established as there will already be gaps there. If the grass has been down for a long time been more work will be involved. The grass should be cut very short and harrowed or scarified hard, you are aiming for at least 50% bare soil
As always when sowing wildflower seeds they do better on poor soil. This is not because they won’t grow on fertile soil but because the species that you don’t want such as grasses, docks, nettles etc will use the fertility better. If the wildflower seeds are sown in the autumn then the gaps in the grasses are likely to close over less quickly. The seed can also be sown in the spring but it is generally better to clear the ground completely.
Ox Eye Daisy
When you have cleared and prepared the ground you need to sow an appropriate wildflower mixture of seed at about 1½ grams to the square metre. You match the wildflower seeds to the conditions and soil type. These are generally done in fairly broad terms such as Clay, Chalk, Sandy or Acid soils. Woodland areas, by a hedge or by water’s edge as examples.
Mixtures of wildflower seeds are generally complex mixes which are designed to give you a range of species in flower over the summer. You cannot guarantee that all will grow but by sowing a complex mixture you should be confident in seeing an interesting and diverse wildflower meadow.
One consideration should be if you have some grass left growing is to sow Yellow Rattle seed on it's own. Or make sure there is yellow rattle seed in the mix you sow. This is a semi parasitic plant that can weaken the existing grass.