"August is bone-dry"

What Seeds to Sow in August

Although August often brings thoughts of harvesting rather than sowing, don't pack away the seed packets just yet. With UK summers increasingly bringing prolonged heatwaves and dry spells, timing is everything. I am hoping for a cooler, damper period to sow, unless I wait until evening, watering the ground well to help seeds establish. The crops I sow now can provide fresh salad leaves before the first frosts, tender vegetables for autumn and winter, or overwintering crops for harvest next spring.

NB: A small range of seed potatoes for planting now for a Christmas crop is available.

I am constructing two new raised beds over summer. In one, I will be sowing salads for winter directly into the soil (or you could start in modules for planting out later), ensuring a steady supply through autumn and into early winter. My choices include hardy lettuces such as Arctic King, wild rocket, chervil, flat-leaved parsley, coriander, land cress, sorrel, winter purslane (Claytonia) and corn salad (lamb's lettuce). During hot weather, I will provide some afternoon shade and keep the soil consistently moist to encourage good germination. Or you might consider starting seeds in modules in a lightly shaded spot where it is easier to keep the compost evenly moist before planting them out.

If you enjoy stir fries, now is a good time to sow oriental vegetables. Pak choi, Chinese cabbage, mizuna, mustards and chop suey greens all perform better when sown in late summer, as the shortening days and cooler temperatures reduce the risk of bolting. The same applies to rocket, spinach, kohl rabi and turnips, which are much happier maturing as temperatures begin to fall.

Towards the end of August, sow spring cabbages, spinach and winter-hardy spring onions, along with Japanese onion varieties such as Senshyu Yellow or Toughball, for overwintering and an early spring harvest. I will sow a selection of fully hardy crops, my favourite kale and/or chicory, winter radish (mooli), mustard spinach, Swiss chard and Perpetual spinach which will continue to provide valuable harvests through autumn and help bridge the 'hungry gap' before the first spring vegetables are ready.

With the increasing likelihood of hot, dry spells in August, a few simple techniques will help improve the germination and establishment of my seedlings.

·        Water the seed drill thoroughly before sowing, then sow into the damp soil and water gently afterwards if needed.

·        Keep the seedbed consistently moist until seedlings emerge, as allowing seeds to dry out during germination can lead to poor results.

·        If the weather is exceptionally hot, provide temporary shade with horticultural fleece, shade netting or even a simple cover raised above the seedlings to protect them from the strongest afternoon sun.

·        Thin seedlings promptly so they are not competing for precious moisture

·        Remember that slugs and snails often reappear in force after summer rain, so keep a close eye on newly emerged plants.

·        Brassica seedlings will also benefit from insect mesh to protect them from cabbage white butterflies and flea beetles.

If you've cleared ground after lifting crops, don't leave the soil bare, especially as heavy downpours following dry weather can quickly wash nutrients from exposed soil. Sow a green manure instead. Fast-growing varieties help suppress weeds, improve soil structure, retain moisture and protect the soil surface. They should be cut down before setting seed and either composted or dug back into the soil. Clover, trefoil, buckwheat, phacelia, grazing rye and winter tares each offer different benefits depending on your soil type and growing conditions.

For my heavy clay soil, grazing rye is one of the best green manures to sow now. Its extensive root system helps improve soil structure, reduces nutrient loss over winter and leaves the ground in better condition for spring cultivation. Where fertility also needs boosting, I mix it with winter tares (vetch), which fix nitrogen while the rye does the hard work of breaking up the soil.

As the other raised bed will only be vacant until late autumn, fast-growing phacelia is an excellent alternative, providing quick ground cover, valuable nectar for pollinators and roots that help improve soil tilth.

One additional tip for clay: don't dig the green manure into wet clay.

Instead, I cut it down in late winter or early spring, leave it on the surface for a week or two to wilt, then lightly incorporate it or leave it as a mulch. This is far kinder to the soil structure (and my back!) than turning over heavy, sticky clay.

August is also an excellent time to sow perennials, biennials and hardy annuals, particularly if you have a sheltered spot where young plants can establish before winter. Sow winter flowering pansies now for a display over winter, or violas to overwinter for colour in Spring. Hardy annuals such as poppies, cornflowers, calendula, Californian poppies and larkspur will bring early flowers next year. 

Although the days are beginning to shorten, the soil is still warm, making August one of the best months for quick germination. Combined with cooler nights as the month progresses, it provides ideal conditions for establishing crops that will keep your kitchen supplied well into autumn, through winter and into the first harvests of spring.

Don't be discouraged if your first sowing struggles during a heatwave. A second sowing a week or two later, once temperatures moderate, often catches up quickly and can produce the stronger crop.