What To Do In The Garden This August
August's main jobs are consistent watering, regular deadheading and staying ahead of pests before they establish. North London's warmer, more sheltered microclimate means borders and containers both dry out faster than the forecast suggests, so daily checks matter more than sticking to a fixed watering schedule.
- Water deeply in the early morning rather than the evening, so foliage dries before nightfall and moisture reaches the roots rather than evaporating off the surface.
- Deadhead dahlias, roses and other repeat-flowering perennials to keep them producing. Leave hip-forming roses such as Rosa rugosa unclipped for autumn colour.
- Feed containers, hanging baskets and repeat-flowering plants weekly with a high-potash liquid feed.
- Trim lavender and other Mediterranean herbs once flowering finishes, to keep plants compact before winter.
- Cut spent canes of summer-fruiting raspberries to the ground once cropping finishes, and tie in new blackberry and climber growth. Leave autumn-fruiting raspberry canes in place — they're still cropping.
- Raise the mower blade and water lawns deeply but less often through hot spells.
Watering And Care By Space In A London Garden
How you water and care for a garden in August depends more on the type of space than the calendar. A shaded Victorian back garden, a sun-baked roof terrace and a north-facing balcony all need a different rhythm through a London summer.
| Garden Type | Watering Rhythm | Main Risk This Month | Boma Tip |
|---|---|---|---|
| Established Borders & Beds | Deep water once or twice a week in dry spells, rather than little and often | Clay soil capping and cracking as it dries | Top up an existing mulch layer to slow evaporation — a fresh full application is better saved for autumn |
| Patios & Courtyard Containers | Check daily; water when the top 2–3cm of compost feels dry | Compost drying out and pulling away from the pot | A tub and basket compost formulated for containers holds moisture better than garden compost — see our compost FAQ guide |
| Roof Terraces & Balconies | Water morning and evening in full sun and wind | Wind stripping moisture faster than sun alone | Group pots together to buffer wind and raise humidity around the foliage |
| Window Boxes & Hanging Baskets | Water daily, sometimes twice in hot spells | Small compost volume dries out fastest of all | Choose self-watering liners or reservoir baskets to cut down the daily workload |
What To Plant In August
August favours planting over sowing. Most popular seeds — including sunflowers and runner beans — no longer have time to mature before the first frosts, so this is a month for buying young plants, quick vegetable sowings, and bulbs that reward patience with very little of it.
Buy Young Biennials Rather Than Sow From Seed
The window for direct-sowing hardy biennials such as Digitalis purpurea (foxglove) and Dianthus barbatus (sweet William) runs from May to July, and has effectively closed outdoors by August. Buying young, pot-grown biennials now is the better route to a spring display — plants such as Digitalis purpurea 'Lucas Pink' can go straight into their final position while the soil is still warm, and will establish well before winter.
Quick Vegetables And Salad Crops
A handful of vegetables still have time to mature before autumn. Lettuce, kale and radish can all be sown direct now, and spinach and turnips will crop through into October if kept consistently moist.
Ready-Grown Plants For Instant Colour
For flowers this year rather than next, buy plants already in bud or flower rather than sowing from seed. Pot-grown dahlias, cosmos and marigolds from Boma's bedding plants range go straight into a border or container and keep flowering into autumn.
Trees And Shrubs
Warm soil in August gives trees and shrubs a head start on root establishment before winter. Olive trees and bay trees planted now settle in well before the first frosts, and both suit pot culture on a terrace or courtyard as well as open ground.
Bulbs For Autumn Colour
Colchicum corms planted now are one of the more instantly rewarding jobs in the August garden — they push up flowers within a few weeks, without needing to be planted deep or watered in specially. Nerine bowdenii bulbs can also go in now, in a sunny, sheltered spot, though a freshly planted or divided bulb often doesn't flower until its second autumn — treat the first year as establishment rather than display.
Guarding Against Pests And Problems In August
Warm, humid August weather favours tomato blight, powdery mildew, aphids and slugs, and London gardens have a particular disadvantage: reduced air circulation between buildings holds heat and moisture around plants for longer than in a more open garden.
- Inspect leaves top and bottom twice a week for early aphid clusters and the first signs of mildew.
- Remove and destroy blighted foliage promptly rather than composting it.
- Water in the morning rather than the evening — damp evening foliage is what draws slugs out to feed. An RHS trial found common barrier methods, including copper tape, made little practical difference in a realistic garden setting; hand-picking after dark remains one of the more reliable controls in a small courtyard or container garden.
- Choose resistant varieties from Boma's outdoor plants range where blight or mildew has been a recurring problem.
Boma Garden Centre is at 51–53 Islip Street, Kentish Town NW5 2DL. Bring in an affected leaf or a photograph and the team in store can help identify a problem on the spot. We deliver to all M25 postcodes, with charges zoned by postcode from £10 — useful for keeping window boxes and containers topped up with compost and feed through the rest of the summer. Check delivery zones and charges.
If an established border has become tired by midsummer, or a section needs replanting rather than nursing through to next year, Boma's Garden Planting Service covers consultation, clearance of existing plantings and a considered new scheme within a 5-mile radius of Kentish Town. For courtyards, roof terraces and balcony containers specifically, the Courtyard & Roof Terrace Container Planting Service covers the same ground for smaller, more exposed spaces.
Frequently Asked Questions
Can I still sow flowers or vegetables in August in London?
Some, yes. Lettuce, kale, radish, spinach and turnips can all still be sown direct for an autumn crop. Flowers with a longer season, including sunflowers and runner beans, no longer have time to mature from seed this late — buy young plants instead if you want them this year.
Is it too late to plant tomatoes in London?
For outdoor tomatoes from seed, yes — there's no longer enough of the growing season left. Established plants already fruiting can keep cropping into September under a warm wall or in a sheltered courtyard, but a new plant started from seed in August won't produce a worthwhile harvest before the first frosts.
How often should containers be watered in a heatwave?
Check daily, and water whenever the top few centimetres of compost feel dry — on a windy roof terrace in a heatwave that can mean twice a day. Established borders generally prefer a deep soak once or twice a week over frequent light watering, which encourages roots to stay near the surface.
What's the most effective way to deal with slugs in a London garden?
Water in the morning rather than the evening, since damp evening foliage is what draws slugs out to feed. An RHS trial found common physical barriers, including copper tape, made little measurable difference in a realistic garden setting — hand-picking after dark is still one of the more reliable controls in a small courtyard or container garden.
Should I feed my plants in August?
Containers, hanging baskets and repeat-flowering plants benefit from a weekly high-potash liquid feed to keep them blooming into autumn. Established shrubs and perennials in the ground need little or no extra feed this late in the season, since soft new growth now is more vulnerable to the first frosts.
Boma Garden Centre is at 51–53 Islip Street, Kentish Town NW5 2DL, with pot-grown biennials, late-summer bedding, colchicum corms, compost and feed to see your garden through to autumn. Order for delivery across the M25, or come in and speak to the team about anything that needs attention before the season turns.
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