August is a great time to sow seeds and plant young plants in the UK. On the vegetable patch, sowing and planting out now will keep your cropping season going, providing you with short-term harvests of salad leaves and other quick-growing crops such as radishes, along with longer-cropping plants like winter cabbages. For veg that need a bit of time to crop well, planting in August will ensure plants get plenty of sunshine and warm temperatures before autumn sets in.
In ornamental borders and cuttings patches, August is a great time to get ahead and plan for the following year. Sowing hardy annuals now will give you an early crop of flowers in spring, while biennials sown in August will flower by the following summer.
Bear in mind that, while warm August temperatures are perfect for aiding seed germination, the water table is lower so you may need to provide additional water to seedlings and newly planted plants.
Vegetables to plant in August
Hardier than they look, lettuces can be overwintered in greenhouses and beneath cloches, for picking leaves from April through to June.
Sown in late August, spinach can provide a crop of young leaves in October and then enter dormancy over winter, ready to provide a fresh crop of leaves in early spring. survive harsh frosts and rain. Sow direct in well-prepared, fertile soil, and cover with a low cloche when temperatures start to fall.
Fast germination makes oriental leaves satisfying to sow, whether direct in soil or in modules for planting out. The latter method works better in wet summers (slugs may eat rows of seedlings in a night). Sow three seeds per module, and thin to one or two plants. Cover with a cloche as temperatures begin to fall in autumn.
Watch Monty Don sow oriental leaves in this clip from Gardeners’ World:
- How to sow winter salad crops
- Buy modular seed trays on Thompson & Morgan
- Buy oriental leaves seed mix from Thompson & Morgan
Wild rocket sown in early August will provide you with a crop of fresh leaves before winter, and then lie dormant until March, when it will put on new growth. Salad rocket stands the best chance of surviving frosts if sown in late August. It also offers more leaves in winter than wild rocket, but often bolts in April.
Corn salad is a delicious leaf crop that crops throughout winter. Sow direct in well-prepared soil and cover with a cloche when temperatures start to drop. Corn salad roots are shallow, so water regularly if under cover or in otherwise dry conditions.
Onions don’t germinate well in temperatures regularly above 20°C, so bear this in mind when sowing in August. Either sow direct in rows outdoors, with seed covered by 2cm of soil, or in modules, with up to 10 seeds in each, for a harvestable ‘clump’ in spring.
Turnips are best sown direct and then thinned. Sow seeds sparingly because, although they’re tiny, they all seem to germinate and subsequent growth is rapid. Thin in late August or early September. Module-sown seed can be thinned to two or three roots in each, for planting out in late August. Fleece or mesh help keep pigeons, butterflies and cabbage root fly at bay.
Hardy chicory can be sown from February to September for a long cropping season, so continue sowing in August for a harvest over winter. Start the seeds off in a seed tray, before planting out in a sunny spot.
Spring cabbages can be sown direct outdoors, or indoors in modules to be planted out later, while winter cabbages grown from seed in previous months should be planted out now. Protect from cabbage white caterpillars and pigeons using fine netting suspended 1m off the ground to protect hedgehogs, or a bespoke cage.
Chard can be successionally sown throughout spring and summer, but August is your last chance to make a sowing for a winter crop. Sow direct in shallow drills or in pots of moist, peat-free compost.
Japanese onions are bred to withstand winter cold and now is the time to sow them. Cultivars to sow and grow include ‘Senshyu’ and ‘Radar’.
- Buy Japanese onion seeds from Crocus
Sow kohlrabi as soon as you can in August, for a late harvest in October. Both the leaves and swollen stems can be eaten – enjoy them roasted, stewed or raw.
Flowers to plant in August
Pot marigold (Calendula)
Colourful and easy to grow, Calendula can be sown in August and September, for flowers in the following spring. They’re hardy, so simply direct sow them where they are to flower, either in shallow drills on the ground or in pots.
- Buy Calendula seeds from Thompson & Morgan
As with pot marigold, you can sow cornflowers (Centaurea cyanus) in August for May flowers. Cultivars to sow and grow include ‘Black Ball’, which has deep chocolate-coloured blooms, and ‘Blue Ball’. Sow direct in shallow drills in the soil or on the surface of moist, peat-free compost in pots.
- Buy cornflower seeds from Thompson & Morgan
Forget-me-nots (Myosotis sylvatica) can be sown throughout the summer months and into September. A useful ground cover plant for shade, they make a fine companion plant with tulips, and will readily self-seed once established. Sow in seed trays for planting out in spring or direct when you want them to grow.
Despite their vivid, exotic appearance, California poppies, Eschscholzia californica, are hardy annuals, and will survive a winter outdoors. Simply sow where you want them to flower, wither in shallow drills in well-prepared beds or on the surface of moist peat-free compost in pots.
- Buy California poppy seeds from Thompson & Morgan
Wild carrot or Queen Anne’s lace (Daucus carota) looks magnificent as part of a wildlife garden. Choose a sunny, well-drained spot for this biennial and sow in well-prepared soil where you’d like it to flower.
- Buy wild carrot seeds from Crocus