No Mow May

From the RHS website:

If you want to encourage wildflowers in your lawn, try No Mow May. As the name suggests, you simply stop mowing in early May, which allows the wild plants already in your lawn to grow up and flower, adding colour and attracting pollinating insects and other wildlife. You can leave your whole lawn uncut or just a section.  community, or giving a second life to ingredients that most commonly go to waste