What to plant in August

What to plant in August

A practical UK guide to sowing in the glut month - what still goes in, what fills the gaps left by lifted crops, and why an empty August bed costs you all winter.

August is the month the garden gives everything back. Courgettes are arriving faster than you can eat them, the beans are climbing over the top of their canes, tomatoes are ripening on the vine, and there is a bowl of something on the kitchen table every single day. It is the most rewarding month of the year, and it is also the month almost everybody stops sowing.

That is the trap. While you are picking, whole beds are emptying out. The onions come up, the garlic comes up, the early potatoes come out, the broad beans and peas finish. By the end of August a plot that was full in June can be half bare, and once the light goes in September nothing you sow will amount to much. The gardeners who eat well from November to April are the ones who kept a seed packet in their pocket through August.

If July was about the last of the summer sowings, August is the pivot. Half of it is harvest and storage, and half of it is next season. Both matter (RHS August jobs).

What vegetables can I sow in August?

More than most people think. Spring cabbage, winter lettuce, oriental leaves, rocket, corn salad, land cress, winter spinach, perpetual spinach and chard, turnips, radish, spring onions, overwintering onions from seed, kohlrabi, and a range of herbs can all be sown in August. The soil is warm and damp, germination is fast, and the crops that go in now are the ones you eat when the shops are charging most for them.

Spring cabbage is the classic August sowing and the single most valuable thing you can put in this month. Sow 1 to 2cm deep in modules or a seed bed in the first three weeks of August, transplant in late September or early October at 30cm spacing, and you cut fresh greens from March into April, right in the middle of the hungry gap (RHS cabbage guide). April, Duncan, Wheelers Imperial and Pixie are all reliable. Plant them a little closer than the packet says and you can cut every other one as spring greens before the rest heart up.

Oriental leaves are at their absolute best sown in August. Pak choi, mizuna, mustard (Red Frills, Green in the Snow), komatsuna and Chinese cabbage all bolt if you sow them in spring, because lengthening days push them to seed. Sow them as the days shorten and they behave. 1cm deep, 20 to 30cm apart for full heads, or scatter thinly and cut as baby leaves in four to five weeks. Net them, because flea beetle will pepper the leaves with holes otherwise.

Winter lettuce goes in from early August. Sow on the surface, barely covered, and thin to 20 to 25cm. Choose the hardy types rather than the summer ones: Winter Density, Arctic King, Valdor and Winter Gem will stand outside in most of the UK and crop through into spring under a cloche. Sown now they establish while the soil is warm, which is the whole point.

Rocket is happier in autumn than it ever is in summer. Sown in August it grows fast, tastes less fiery, and bolts far more slowly. Sow thinly, 1cm deep, thin to 15cm, and cut leaves from four weeks. Keep sowing until mid-September.

Corn salad (lamb's lettuce) and land cress are the two crops that will still be feeding you in January. Both are properly hardy. Corn salad goes in 1cm deep, thinned to 10cm. Land cress tastes like watercress, self-seeds happily, and shrugs off frost. Neither is fast, which is exactly why they need sowing now rather than in October.

Winter spinach should be sown in the second half of August. Varieties like Giant Winter and Medania are bred for it. 2 to 3cm deep, thin to 15cm. It puts on growth through September and October, sits out the worst of the winter, then grows away hard in February and March when nothing else is moving.

Perpetual spinach and chard can still go in during early August. 2cm deep, 30cm spacing. Sown now they crop through autumn, survive the winter, and produce again in spring. A single August sowing can feed you for eight months.

Turnips are worth a final sowing in the first two weeks of August. 1 to 2cm deep, thin to 10 to 15cm. Pull them at golf-ball size in six to eight weeks. You can also sow turnips thickly and simply cut the tops as turnip greens through winter, which is an old trick and a good one.

Radish is still the fastest thing in the garden and remains useful right through August. 1cm deep, 3 to 5cm apart, four weeks to the plate. Late in the month you can also sow winter radish like Black Spanish Round or mooli, which take ten to twelve weeks and store in the ground.

Spring onions sown in August need to be the overwintering types. White Lisbon Winter Hardy is the standard and it works. Sow in clumps of six to eight seeds, 25cm apart, 1cm deep, and you will be pulling them next April and May.

Overwintering onions from seed go in from mid-August to early September in most of the UK. Senshyu Yellow and Radar are the varieties to look for. Sow 1cm deep and thin to 10cm. They will be ready to lift in June, several weeks before spring-planted sets. If sowing feels like a faff, order Japanese onion sets now and plant them in September or October instead.

Kohlrabi can be squeezed in during the first week of August. 1cm deep, 20cm apart, eight to ten weeks to a tennis-ball-sized bulb. Any later and it will not size up.

Dwarf French beans are a gamble worth taking in the south in the first few days of August. 5cm deep, 15cm apart, roughly eight weeks to first pods, which puts you at the very end of September. If you get an early cold snap you lose them. In the Midlands and further north, do not bother.

Herbs are easy wins now. Coriander and chervil both prefer the cooling weather and will not bolt the way they do in June. Parsley sown in August gives you leaves through winter if you cover it with a cloche. All three go in 1cm deep, thinned to 15 to 20cm.

What should I sow now to eat over winter?

The crops that carry you through the cold months are salads and leaves, and August is their sowing window. Spring cabbage, winter lettuce, corn salad, land cress, oriental leaves, winter spinach and chard sown now will still be giving you something to cut in January and February (RHS winter vegetables).

The thing to understand is the ten-hour rule. Once daylight drops below about ten hours a day, which happens in early November across most of the UK, plants effectively stop growing. They sit there, alive, and you harvest from them, but they put on almost no new growth until the light returns in February. Everything you eat in December was grown in September and October. That is why a sowing on 10 August and the same sowing on 10 September produce completely different results.

So the practical rule for winter is simple: get it in the ground by the end of August so it has September and October to bulk up.

Cover is the other half of it. None of these crops need heat, but they hate wet leaves and battering rain. A cloche, a cold frame, or an unheated greenhouse or polytunnel does not raise the temperature much, but it keeps the rain off, and that is the difference between a lettuce that stands until March and a lettuce that rots in December. If you have a greenhouse that emptied out when the tomatoes finished, clear it in September and fill it with winter salad. Fleece over hoops is the cheapest version and works nearly as well.

How do I make the most of beds emptying in August?

Fill them within days, not weeks. Onions and garlic come out in July and early August, potatoes are lifted, broad beans and peas finish. Those gaps are the biggest growing opportunity of the year, and left alone they will be a mat of weeds by October (RHS succession sowing).

You have three options for every empty bed, and you should be picking one deliberately rather than defaulting to nothing.

One: sow a fast catch crop. Radish in four weeks, rocket and cut-and-come-again salad in four to five, oriental leaves in five, turnips in six to eight. After onions and garlic the ground is usually clean and easy to rake down, which makes it ideal for small seed.

Two: sow the winter crop that belongs there. Spring cabbage after the potatoes. Winter lettuce and corn salad after the peas. Overwintering onions after the beans. This is the highest-value option, because it turns a gap into food in March.

Three: sow a green manure. This is the one most people skip and it is a genuinely important August job. A green manure is a crop you grow to feed the soil rather than yourself. It covers bare ground, stops nutrients washing out over winter, suppresses weeds, and adds organic matter when you cut it down.

For an August sowing:

• Phacelia - fast, beautiful, brilliant for bees if you let some flower. Broadcast at roughly 2g per square metre. Not frost hardy in a cold winter, which is fine, it dies down and mulches itself.

• Field beans - hardy, nitrogen fixing, good on heavy soil. Sow 5cm deep, 15 to 20cm apart. Dig in or cut down in spring.

• Grazing rye - the toughest overwinterer, superb at holding soil together and mopping up nitrogen. Broadcast at 15 to 20g per square metre. Cut it down four weeks before you want to sow into the bed.

• Crimson clover - nitrogen fixing, sow by mid-August so it establishes before the cold.

Cut green manures down before they flower and set seed, and either dig them in or leave them on the surface as a mulch if you are no-dig. Either way, you go into spring with soil that is in better shape than the day you emptied the bed.

What should I be harvesting in August?

Everything. August is the glut, and the skill this month is less about growing than about not wasting what you have grown.

Courgettes need picking every two to three days at finger to hand length. Miss a couple of days in August and you have a marrow. Keep picking and the plant keeps producing, which is either the good news or the bad news depending on how many you planted. If the glut has beaten you, grate and freeze the surplus in bags, ready for soups and cakes, or slice and griddle it and keep it in oil.

Runner and French beans must be picked every two or three days for the same reason. A pod left to swell tells the plant it has done its job and cropping slows. Surplus beans freeze well after two minutes in boiling water and a plunge into cold.

Tomatoes are ripening now. Keep removing side shoots on cordon types, and around mid-August pinch out the growing tip two leaves above the top truss so the plant puts its energy into ripening what it has rather than making more.

Cucumbers, sweetcorn, peas, salad, early apples, plums and blackberries are all coming in through the month. Sweetcorn is ready when the tassels go brown and a pressed kernel runs milky. Eat it the same hour if you possibly can.

Onions and garlic need curing, not just lifting. Once the foliage flops and yellows, ease them out and dry them somewhere warm, airy and out of the rain for two to three weeks until the necks are papery. Cured properly, onions keep until spring. Lifted and thrown in a bag, they rot by October.

Maincrop potatoes start coming out from late August. Wait until the haulm has died back, leave them in the ground a fortnight to set their skins, then lift on a dry day and store in paper or hessian sacks in the dark.

There are three other jobs that pay you back next year and are easy to forget while you are picking. Peg down strawberry runners into pots of compost now and you have free plants for a new bed in autumn (RHS strawberry guide). Save seed from your best open-pollinated plants, letting a couple of good lettuces, beans or tomatoes go to seed rather than pulling them. And order garlic and autumn onion sets now for planting in October and November, because the good varieties sell out by September.

What flowers can I sow in August?

Hardy annuals, and this is the tip most people miss. Calendula, cornflower, larkspur, poppies, ammi, nigella and scabious sown in the last two weeks of August will germinate in warm soil, put down a proper root system through autumn, sit out the winter as small tough plants, and then flower four to six weeks earlier and considerably bigger than anything you sow next spring (RHS plants for pollinators).

Sow direct where they are to flower, thinly, at about 1cm deep, and thin in spring rather than autumn. On heavy wet soil, sow in modules instead and overwinter them in a cold frame, because it is winter wet rather than winter cold that kills them.

The other flower jobs this month are ordering and planning. Spring bulb catalogues are out now and the best daffodil, tulip and allium varieties go early. Order in August, plant daffodils and alliums from September, and hold tulips back until November when the soil is cold enough to reduce the risk of tulip fire. Autumn-flowering bulbs like colchicum and autumn crocus need planting now if you want them this year.

What is too late to start in August?

Most of the summer garden. Do not waste seed, compost or bed space on these.

• Winter brassicas - Brussels sprouts, purple sprouting broccoli, kale, savoy cabbage and overwintering cauliflower all needed sowing by June. The window has closed. Buy young plants if you can still find them.

• Maincrop carrots - not enough season left to make a root worth pulling.

• Beetroot - borderline in the first week of August in the south, pointless after that.

• Sweetcorn, courgettes, squash and pumpkins - long-season crops that needed to be in by June.

• Runner and climbing beans - too late everywhere.

• Peas - a very early August sowing of a fast variety in the far south might just make it. Everywhere else, no.

• Leeks and parsnips - both needed sowing in spring.

• Garlic - not too late, but too early. Wait for October and November.

• Tomatoes, peppers, chillies and aubergines - not a chance from seed.

August sowing reference table

Depths and spacings based on RHS vegetable sowing recommendations.

What should I do first if August has caught me out?

If the beans and courgettes have taken over your life and you have not sown a thing since June, pick three jobs and do them properly this week.

• Sow spring cabbage. One tray of modules, twenty minutes, and you are eating fresh greens in March when everyone else is buying them.

• Sow a tray of oriental leaves and winter lettuce. Fast, forgiving, and they turn your empty September beds into salad.

• Broadcast a green manure over anything you are not going to plant. Ten minutes with a bag of phacelia or rye beats six months of weeding.

Then do the storage jobs properly. Cure the onions and garlic somewhere dry and airy, lift the maincrop potatoes on a dry day and get them into the dark, and freeze what you cannot eat. A glut wasted in August is a shopping bill in January.

Knowing which bed emptied when, and what actually went back into it, is the difference between guessing and having a system. myPatch tracks your beds, your sowings, and your local weather, so next August you already know what came out, what should go in, and how long you have got.

August is not the end of the growing year. It is the start of the next one.