August Is the Quiet Month Everyone Assumes Means No Work. A Few Jobs Say Otherwise.

August looks like a continuation of July, which is exactly why it gets ignored. Hampstead in north London averages 67.7 mm of rain in August against 50.5 mm in July, and about 188 hours of sun against 200 (Met Office, 1991 to 2020). Daytime highs are almost the same, 22.3°C. The real change is that hedges have little growth left before cold weather stops them, and that single fact is why the hedge cut has to come before anything else on this list.

Should you cut the hedge in August?

The RHS recommends giving hedges a final trim in August, because they will grow only a little before cold weather stops growth. Its pruning guide times many hedges for late summer: beech once, holly once, hornbeam from mid to late summer. The RSPB, by contrast, advises cutting only between 1 September and 28 February. Nesting is where the two disagree.

The law does not set a closed season for garden hedges. The offence is damaging a nest in use or being built. Our rule of thumb errs on the side of caution. Wait until September where the hedge allows it, because the RSPB's guidance is safer for birds, and only cut in August when the plant itself forces the issue, with a proper nest check first.

Plant type matters. The RHS says trimming conifer hedges after August can cause bare patches, and most conifers do not regrow from old wood, so a conifer hedge has no safe late option. Trim lightly, mainly the past year's growth, and keep the top narrower than the base so light reaches the lower branches. For a full explanation of the checks, see when to trim a hedge in the UK.

Which jobs come next?

Water for next year's flowers

Rhododendrons, camellias and azaleas form next spring's flower buds now. The RHS says to keep early-flowering shrubs such as camellias and rhododendrons well watered in dry spells, and to soak drought-stressed shrubs and new plantings thoroughly, with stored rainwater where possible. Mid to late August is also the RHS's suggested window for vine weevil nematodes on rhododendrons, camellias and pot-grown fuchsias.

Raise the mower, but do not scarify yet

The RHS says to raise the cutting height, especially on fine lawns, mow lightly and often, and leave short clippings on the grass in hot weather. It says to leave excess thatch until autumn and not to water an established lawn, even in a dry spell. Browning in a hot, dry summer is normal and the grass greens up after rain.

If you plan a new lawn this autumn, the RHS says to clear and dig the ground now, wait a few weeks for weeds to reappear, then hoe them off. Dates for seed are in when to overseed a lawn.

Prune what has flowered

August suits several summer prunings: wisteria and climbing shrubs such as pyracantha after flowering, a light trim of hebes and lavender, and rambling roses that have finished. Deadhead roses, dahlias and penstemons to keep flowers coming into early autumn. The RHS suggests feeding tired containers and borders weekly with a liquid tomato feed.

Sow, divide and take cuttings

Sow hardy annuals straight into borders in late August to overwinter. Take cuttings of pelargoniums and other tender perennials as soon as possible and grow them on in a greenhouse, cool conservatory or bright windowsill. Collect seed from plants you want to repeat.

What should you leave alone?

• Ornamental grasses. The RHS says to leave the flowerheads standing for winter interest.
• Autumn lawn work. Scarifying, overseeding and, if the grass is struggling, an autumn feed follow in September and October.
• Black spot sprays on roses. The RHS recommends against using fungicides for rose black spot, and says to collect and destroy fallen leaves in autumn or bury them under mulch.

If the late-summer cut is more than you want to take on, or the hedge is tall, our hedge trimming and pruning service covers it, and we take the clippings away. A free garden visit is followed by a written quote. Before this, read July; next is September.

Sources

• Met Office: Hampstead climate averages, 1991 to 2020
• RHS: August jobs
• RHS: August trees and shrubs
• RHS: August lawns
• RHS: August flowers
• RHS: September lawns
• RHS: Rose black spot
• RHS: Lawn care in autumn
• RHS: Pruning hedges
• RHS: How to trim a hedge
• RSPB: Birds' nests and nestboxes

This reflects our own read of what matters most in London and Hertfordshire gardens this month, not a guaranteed task list for yours. Nesting activity and weather both vary year to year, so use it as a guide — get in touch if you'd like a hand with any of it.