In August you can still sow plenty of vegetables for a fresh autumn and winter harvest. Fast leafy crops like lettuce, spinach, rocket, radish, chard and Asian salad leaves will be on your plate in around six weeks. Overwinterers such as lamb’s lettuce, winter purslane and winter spinach go in now for harvests from October right through to early spring (Velt, Tuiniertijd). With lettuce and spinach, do pick proper winter varieties, because those handle the cold far better (Velt).
Plenty of people think the veg garden season is more or less over by August. Nonsense. You are not just harvesting flat out, you can refill your empty patches straight away. I (Fred) spent years making the mistake of leaving my beds bare after the summer harvest. Such a waste. With a few packets of seed and the right timing, you will be picking fresh leaves from your own garden deep into winter. In this article you will read exactly what you can still sow now, how deep, at what temperature it germinates, and when you harvest.
What can you still sow in August?
Broadly speaking there are two groups: fast autumn crops you harvest this year, and overwinterers you sow now but that only really deliver in spring. It pays to keep that difference clear in your head, because most gardening sites lump them together.
Fast autumn harvest (ready in about six weeks): loose-leaf lettuce, rocket, spinach, radish, chard, turnip tops, garden cress, and Asian leaves such as pak choi, mizuna, tatsoi and mustard (Moesmeisje, Makkelijke Moestuin).
Overwinterers for autumn through to early spring: lamb’s lettuce, winter purslane, winter spinach, winter lettuce varieties, and chard (Tuiniertijd, Velt).
Planting out (module-raised plants you can still put in now): winter kale, winter cauliflower, endive, kohlrabi and winter leeks (Moesmeisje, Moestuinweetjes).
August sowing table: depth, germination temperature and harvest
Below is the full table you will not find on the other sites: for each crop, whether you sow direct or plant out, the sowing depth, the germination temperature and when you harvest. The sowing depths are general rules of thumb (fine seed shallow, larger seed slightly deeper); germination temperatures come, where known, from the table by Moestuinmania.
| Crop | Sowing | Sowing depth | Germination temp. | Harvest | Hardy? |
|---|---|---|---|---|---|
| Radish | direct | ~1 cm | 10-20 °C | 4-8 weeks | no, autumn crop |
| Rocket | direct | ~1 cm | cool is best | ~6 weeks | partly, picks into winter |
| Spinach (winter variety) | direct, from mid-Aug | ~2 cm | 16-18 °C | autumn, and March-April | yes (winter variety) |
| Lamb’s lettuce | direct | ~0.5-1 cm | 10-15 °C | Sept-January | very hardy |
| Winter purslane | direct | shallow | cool | Oct-March | very hardy |
| Chard | direct | ~2 cm | 12-18 °C | ~6 weeks of picking | moderate |
| Lettuce / loose-leaf | direct or raise in modules | shallow, needs light | 15-20 °C | ~6 weeks | winter varieties yes |
| Garden cress | direct | very shallow | cool | 2-3 weeks | no |
| Turnip tops | direct | ~1-2 cm | cool | a few weeks | moderate |
| Pak choi / mizuna / tatsoi | direct | ~1 cm | cool | 6-8 weeks | moderate |
| Endive | plant out | shallow | – | autumn | moderate, frost-sensitive |
| Kohlrabi | plant out | ~1 cm | – | autumn | moderate |
| Winter kale | plant out | ~1.5 cm | 13-20 °C | Sept-March | very hardy |
Source for germination temperatures: Moestuinmania. Radishes need roughly 50 to 60 days to mature (Allezadenkopen). Kale is usually sown back in May or June; in August you put the young plants out (Tuiniertijd).
What should you stop sowing in August?
Just as important: what to leave alone now. Heat-loving fruiting crops like tomato, courgette, cucumber, aubergine, pepper and climbing or dwarf beans are off the August sowing list.
The reason is simple. Those crops need a long, warm growing season to set fruit and ripen it, and they are not frost hardy. After August there are too few warm, bright days left before the first night frost arrives. At best you will get a few flowers, but no ripe harvest. That is why in August these crops sit in the harvesting section of the garden calendar, not the sowing section (Gardeners World).
In short: August is the month of leafy greens and hardy types, not summer fruits.
Why is my lettuce germinating so badly in August?
This is the question almost nobody answers, and it is exactly what ruins so many August sowings. Lettuce seed hates heat. Above 25 °C lettuce seed goes dormant: it stays alive, but refuses to germinate until things cool down (Gardeners World). That is called thermodormancy. At the other end, it needs at least 6 °C to germinate at all (Gardeners World).
So on a warm August day with soil temperatures above 25 °C you simply get no seedlings, no matter how well you sow. Your seed is not bad, it is too hot.
Here is how to get around it:
- Sow at the coolest moment. Sow in the evening, once the soil has cooled, and keep the seed drill moist and cool (Velt).
- Sow in the shade. Put your lettuce bed in the shade of a taller crop, or stretch shade netting over it. A sheltered, shady spot also helps against bolting (Moestuinweetjes).
- Raise plants somewhere cool. Sow into a seed tray in a cooler spot, indoors or in the shade, then plant the young plants out.
- Sow shallow. Lettuce seed needs light to germinate. Cover it with a thin layer of sieved compost and water from below, so you do not wash the seed away (Gardeners World).
Keep the soil moist for every August sowing until everything is up. A dried-out seed drill is the most common mistake of the month.
Overwinterers: sow now for early spring
Alongside the fast autumn harvest, August is the moment to set your spring up in advance. You sow these types now, they overwinter as small plants, and they burst into growth in March and April, long before your new sowings do anything.
- Lamb’s lettuce: sow from late July to September, harvest from September to January (Tuiniertijd). Very hardy and reliable. The easiest winter vegetable there is.
- Winter spinach: sow from August to early October, harvest in March and April after the winter (Tuiniertijd). Choose a proper winter variety.
- Winter purslane: sow in August and September, harvest from October to March (Tuiniertijd). Tender, mild leaves exactly when little else is growing.
- Winter lettuce (winter variety): sowing in mid-August gives small, frost-hardy plants that come through the winter well and form a head in May and June (Gardeners World).
A handy rule of thumb: let your overwinterers go into winter small. A small, hardened-off plant handles frost far better than a big, soft one. Sowing too early or too thickly works against you.
And think about what you still plant in autumn too: garlic goes in the ground from mid-September to mid-November for the best bulbs, harvested from early summer (Makkelijke Moestuin). Winter onions are hardy down to around -15 °C (Makkelijke Moestuin).
How do you protect your autumn and winter vegetables from frost?
Many of the types above are hardy, but a bit of protection extends your harvest considerably and keeps the leaves more tender. Leafy greens are more vulnerable than sturdy brassicas, so cover those sooner (Tuiniertijd).
- Fleece (horticultural fleece): a light, breathable cloth that lets air, light and water through while forming a buffer against frost (Tuiniertijd). Push bamboo canes into the soil and drape the fleece over them like a little tent, so it does not flatten the plants (Gardeners World).
- Low tunnel: stretch the fleece loosely over hoops so it does not rub against the leaves. Snow on top acts as extra insulation; only brush it off vulnerable young plants (Tuiniertijd).
- Cold frame: ideal for young hardy plants and autumn sowings. In October you can still fit lamb’s lettuce, winter purslane, winter lettuce and garlic into a cold frame for a fresh winter harvest (Groei.nl).
Cover in good time. Do not wait until the first hard night frost is forecast and the temperature is already dropping; prevention beats cure (Gardeners World).
What does sowing in August cost?
Not much, and that is exactly the charm. A packet of vegetable seed usually costs between 2 and 4 euros, and you often use it across several seasons (Welkoop). Leafy greens and root crops tend to sit at the lower end of that range, with pricier organic varieties going up to around 6 euros.
Beyond that all you need is some fleece if you want to protect things, and that lasts for years. For a few tenners of seed and fleece you get fresh vegetables from your own garden for half the winter. Work out what a head of lamb’s lettuce or a bag of baby spinach costs in the shop.
Common mistakes when sowing in August
The traps almost everyone falls into:
- Sowing too late. After August the days shorten fast and growth drops off. Waiting until September costs you harvest. Sow your fast leafy greens now.
- Sowing lettuce in full sun and heat. Above 25 °C lettuce seed will not germinate (Gardeners World). Sow cool, in shade, or raise plants first.
- Letting the seed drill dry out. The biggest killer of August sowings. Keep it moist until everything is up (Velt).
- Choosing the wrong variety. Ordinary summer spinach or summer lettuce will not make it through winter. Pick proper winter varieties (Velt).
- Not harvesting in time. Leafy greens bolt or turn tough if you wait too long. Pick regularly (Makkelijke Moestuin).
- Sowing overwinterers too thickly or too early. Big, soft plants freeze sooner than small, hardened ones. Go into winter small.
- Still wanting to sow heat-lovers. Tomato, courgette and beans will not make it now. Leave them be.
Frequently asked questions about sowing in August
Can I still sow carrots in August?
For a proper carrot it is usually too late, as it needs a long growing season. Radish (a fast relative) works fine though: it is ready in 50 to 60 days (Allezadenkopen). Turnip tops and autumn turnips are still possible too.
Which vegetable is easiest to sow in August?
Lamb’s lettuce and radish. Lamb’s lettuce is almost impossible to kill, very hardy, and delivers from September to January (Tuiniertijd). Radish is ready in no time. Perfect starter crops.
Do I need to buy winter varieties or will ordinary seed do?
For spinach and lettuce you want to carry through the winter: buy proper winter varieties. Those handle the cold far better than summer varieties (Velt). For the fast autumn harvest it matters less.
Why is my August sowing not coming up?
Usually one of two things: too warm (lettuce seed will not germinate above 25 °C) or too dry (the seed drill has dried out). Sow cool and keep the soil moist until everything is up (Gardeners World, Velt).
When should I cover with fleece?
As soon as real night frost is expected, and sooner for vulnerable leafy greens than for sturdy brassicas (Tuiniertijd). Cover in good time, not once it is already freezing (Gardeners World).
Can I still sow in September?
Some overwinterers, yes, such as lamb’s lettuce and winter purslane, and in a cold frame you can even manage a bit in October (Groei.nl). But you want most fast leafy greens in the ground in August, while the soil is still warm and the days are long enough.
Want to lay out your autumn veg garden neatly with sturdy planters or raised beds, so covering is easy and the soil stays warm for longer? At Fred’s DIY Plans you will find clear building plans for raised beds and garden projects you can put together yourself. Handy for giving your August sowings a good, warm start. Have a look around and build your own veg garden.