What to Plant in August: Your UK Garden Guide

August has a reputation as the month when British gardening winds down. It is exactly the opposite. What you sow and plant over the next four weeks decides whether your plot is still feeding you in December, and whether your borders start next spring with a bang or a shrug.

The trick is understanding what August actually offers: warm soil, shortening days and, usually, a real risk of drought. Warm soil germinates seed fast. Shortening days mean anything you sow must reach a usable size before growth stalls in late October. And dry ground means most August failures are watering failures, not sowing mistakes.

The August Sowing Rules

Vegetables to Sow in August

Leafy Crops and Winter Salads

This is where August earns its keep. Sown now, these crops crop from October right through to spring, and many will stand outdoors unprotected in most of the UK.

• Winter lettuce - 'Winter Density' and 'Arctic King' are the traditional UK standbys. Sow early August, thin generously.
• Spinach - 'Giant Winter' or 'Medania'. Sow from mid-August once the fiercest heat has passed to avoid bolting.
• Swiss chard and perpetual spinach - 'Bright Lights' or plain 'Fordhook Giant'. Possibly the most forgiving winter crop there is.
• Rocket and mustards - far better sown now than in spring, as cooler nights stop them running to seed.
• Pak choi and mizuna - fast, productive and genuinely happier in autumn conditions.
• Corn salad (lamb's lettuce) and land cress - the toughest of the lot, cropping through frost and snow.

Roots and Brassicas

• Turnips - 'Snowball' or 'Purple Top Milan' will size up in six to eight weeks.
• Winter radish - mooli and 'Black Spanish Round' store well and are a genuinely different crop from summer radish.
• Spring cabbage - 'Durham Early' or 'Wheeler's Imperial' sown early August, transplanted in September for an April harvest.
• Oriental turnip greens and kale - a final sowing in the first fortnight for baby leaves through autumn.
• Spring onions - 'White Lisbon Winter Hardy' overwinters for an early spring pull.

Green Manures for Empty Ground

Any bed you cannot fill with a food crop should go under a green manure rather than sit bare through winter rain. Sow phacelia, field beans, winter tares or grazing rye from mid-August. They suppress weeds, protect soil structure and are dug in or cut down in spring.

August Vegetable Sowing Table

Fruit to Plant in August

August is genuinely the best month of the year for one job in particular: strawberries.

• Strawberry runners planted in August have time to establish a root system before winter, which means a full crop next June. Wait until spring and you will get a token handful. Peg runners from existing plants into 9cm pots, sever once rooted, then plant out 35-45cm apart in fresh ground.
• Container-grown fruit bushes - gooseberries, currants and blueberries can go in now provided you commit to watering them until autumn rain arrives.
• Summer-fruiting raspberries - cut out the canes that just fruited and tie in the new ones. New canes are best planted from November.

If blueberries are on your list, plant into peat-free ericaceous compost rather than garden soil - our complete UK blueberry growing guide covers pH, containers and why rainwater matters so much.

Onions, Garlic and Overwintering Sets

From late August, autumn-planting sets become available and can go straight into prepared ground. They root through autumn, sit out the winter and are ready weeks ahead of spring-planted stock.

• Autumn onion sets - 'Radar', 'Senshyu Yellow' and 'Electric' are the reliable UK choices. Plant from late August into September, 10cm apart, tips just showing.
• Overwintering garlic - hardneck varieties need a cold period to split into cloves properly. Late August is early but workable in northern gardens; most of the UK plants from October.
• Japanese onion seed - can be sown direct in late August in milder regions.

Ground for onions wants to be firm, free-draining and not freshly manured. If your soil is heavy, work in grit or plant into a raised bed - waterlogging over winter is what kills autumn sets, not cold.

Flowers to Sow and Plant in August

Biennials for Next Spring

Biennials sown in July and August produce the cottage-garden spring display everybody wants and almost nobody plans for in time. Sow now, grow on in a seedbed or modules, and plant into final positions in September or October.

• Wallflowers - 'Blood Red', 'Persian Carpet'. Scent and colour from March.
• Foxgloves - 'Excelsior' or the native Digitalis purpurea for a shadier spot.
• Sweet William - a classic June cut flower, sown a year ahead.
• Honesty, forget-me-not and Iceland poppies - all straightforward from an August sowing.

Hardy Annuals: The Best-Kept Secret

Hardy annuals sown in late August overwinter as small plants and flower four to six weeks earlier next year - on considerably bigger, sturdier plants than anything spring-sown. Sow direct where they are to flower, or in modules under cover in colder regions.

• Calendula, cornflower, larkspur, nigella, ammi and orlaya - all excellent from an autumn sowing.
• Sweet peas - sow in deep pots or root trainers late August into September and overwinter in a cold frame.
• Poached egg plant and poppies - simply scatter where you want them and leave well alone.

Bulbs and Perennials

• Autumn-flowering bulbs - colchicum, autumn crocus and nerines go in now for flowers within weeks.
• Madonna lilies - one of the few lilies that wants planting in August, shallowly.
• Order daffodils, alliums and crocus now for September planting. Tulips are the exception and wait until November.
• Divide bearded irises - lift congested clumps, split the rhizomes and replant with the top surface exposed to the sun.

Herbs to Sow and Take Cuttings From

• Parsley - an August sowing gives you leaves right through winter, especially under a cloche.
• Coriander and dill - much less prone to bolting sown now than in midsummer.
• Chervil and winter purslane - both genuinely cold-hardy and cropping when little else is.
• Rosemary, sage, thyme and lavender - take semi-ripe cuttings now. They root readily in August warmth.
• Pot up chives, mint and parsley to bring onto a windowsill before the first frosts.

Looking After August Sowings

Germination is the easy part in August. Keeping seedlings alive through a dry, hot fortnight is where most people lose the crop.

• Water the drill, then sow, then cover. This puts moisture exactly where the seed sits.
• Shade newly sown drills with a plank, fleece or netting until the seedlings appear - then remove it immediately.
• Slugs are worse in late summer than in spring. Protect brassica and lettuce seedlings from day one.
• Net brassicas against cabbage white butterflies, which are at peak numbers now.
• Thin ruthlessly. Crowded autumn seedlings rot rather than grow once the wet arrives.

Regional Timing Across the UK

Jim's Thoughts

August sowing is the least glamorous job in the gardening year and easily the highest-return. Half an hour spent filling the gap left by your broad beans is the difference between a plot that looks sad from October and one that is still producing salad on Christmas Day. Sow early in the month, water the drills properly, and let the shortening days do the rest.