When should I cut back plants if I want to help bees?

The autumn tidy is the most damaging garden habit there is

By October nearly every solitary bee that flew in the summer is dead, and the next generation is sealed in provisioned cells — in hollow stems, in dead wood, in bare ground. Cutting and burning stems, clearing leaf litter and turning over soil destroys them, and nothing about the garden looks any different afterwards. That invisibility is why the habit persists.

Bumblebee queens are hibernating a few centimetres down in undisturbed soil, frequently on a north-facing bank where they will not be warmed into waking early. Digging over a border in November is a direct hazard to them.

A calendar that works

• Early July: cut back catmint, geranium, salvia and marjoram after the first flush. They flower again by late August and fill the gap most gardens have.
• Autumn: leave everything. Seed heads, hollow stems, leaf litter, spent annuals. This is the season where doing less is the whole of the advice.
• Late February to March: cut last year's stems, and lay them somewhere sheltered rather than shredding them — anything still inside will emerge.
• Hedges: cut on a two or three-year rotation, in late winter. Almost all hedgerow species flower on second-year wood, so an annually clipped hedge never flowers at all.
• Ivy: stop clipping it. Ivy only flowers once it reaches adult growth, and a clipped ivy hedge produces no forage in the month it matters most.

The one thing worth cutting in autumn

Grass, in a meadow area, once the wildflowers have set seed — and then only if the cuttings are removed. Leaving them mulches the ground and raises fertility, which is exactly what lets grasses out-compete the flowers. That is the single case where autumn cutting helps rather than harms.