How to Grow Lettuce: A Practical Guide from Seed to Harvest

Lettuce is one of the easiest vegetables to grow, but there’s a little more to getting a good crop than scattering a packet of seed and hoping for the best. The main thing is don’t sow everything in one go — plant seeds every few weeks so you can keep a steady harvest.

You don’t need much space either. Lettuce is perfectly happy in the ground, raised beds, pots and window boxes. We plant a few lettuces under the runner beans early in the season or in small pots in the greenhouse.

Give it decent soil, regular water and, of course, protection from slugs, and you can be picking fresh leaves for much of the year.

When to Sow

Lettuce has a wonderfully long sowing season. You can start under cover from February or March and continue sowing outdoors through spring and summer. With suitable varieties like Arctic King and a bit of protection, you can keep going into autumn too.

The big mistake you can still make is sowing far too much at once. Twenty lettuces all reaching maturity in the same week usually results in a few plants bolting.

Sow a small amount every two or three weeks. Half a short row or a pinch of seed in a module tray is usually plenty.

During hot summer weather, lettuce seed doesn’t germinate very well and plants can easily bolt. It is best to find a cool spot for your seeds and then shade the plants in the worst of the heat.

Don't forget autumn either. Winter varieties grown under a cloche, cold frame or in an unheated greenhouse can provide leaves surprisingly late in the year. With some protection, this can also give you really early lettuce in spring.

Sowing and Growing Seedlings

I tend to start in pots, as you can plant the young plants out when they are established and stronger.

For direct sowing, make a shallow drill about 1cm deep, water it if the ground is dry and sow the seeds thinly. Cover lightly with soil and keep the area damp while they germinate.

For modules, sow one or two seeds into each cell of multipurpose compost. If both grow, keep the strongest seedling. Put them somewhere light and don't let the compost dry out.

Lettuce usually germinates quickly in reasonable conditions, often within a week.

One thing worth knowing is that lettuce seed dislikes excessive heat. During a hot spell, a tray baking in a greenhouse can actually germinate worse than one kept somewhere cooler.

Once seedlings have a few proper leaves, they're ready to plant out. Don't leave them sitting cramped in tiny modules for weeks. Young, actively growing lettuce establishes far quicker than pot-bound plants.

Planting Out and Spacing

Plant lettuce into reasonably fertile, moisture-retentive soil in sun or light shade. In spring, a sunny spot is ideal, but during summer a little afternoon shade can actually be an advantage because it keeps plants cooler and helps slow down bolting.

Spacing depends on what you're growing.

For full-sized lettuces, somewhere around 25–30cm between plants is a good starting point. Smaller varieties can be closer, while lettuces grown purely for young leaves can be much closer together.

Don't bury the centre of the plant when planting out. Keep the growing point just above soil level and gently firm the soil around the roots.

Water them in properly, even if rain is forecast. It settles the soil around the root ball and gives them a good start.

Lettuce is also brilliant for filling temporary gaps. I often squeeze a few plants between crops that won't need the space for another month or two.

Thinning and Growing On

If you've sown directly, you'll almost certainly need to do some thinning. Lettuce seed has a habit of landing exactly where the previous seed landed, however carefully you thought you were sowing it.

Thin seedlings before they become badly crowded. You can start by leaving a few centimetres between plants, then thin again as they grow until the remaining lettuces have the spacing they need.

The nice thing is that the later thinnings don't have to be wasted. Once they're large enough, young leaves can go straight into a salad.

Keep weeds down while the plants are small, but be gentle around them. Lettuce roots are fairly shallow and easily damaged.

If you're growing loose-leaf or cut-and-come-again varieties, you don't necessarily need to grow enormous individual plants. Harvesting the outside leaves regularly keeps them producing.

For heading lettuces, give them their proper space and let them develop.

And keep an eye out for plants beginning to stretch upwards. Once a lettuce decides it's going to flower, there's very little persuading it otherwise. Harvest it and make room for the next batch.

Watering and Feeding

Lettuce is mostly water, so it isn't surprising that it grows best when moisture is reasonably consistent.

Don't keep the ground permanently soggy, but try not to let plants repeatedly wilt either. A good watering during dry weather is far better than a tiny splash on the surface every evening.

Pay particular attention to lettuce growing in containers. A full pot of leafy plants can dry out remarkably quickly on a warm day.

I prefer watering the soil around the plants rather than continually wetting the leaves, particularly later in the day. Morning watering is ideal when you have the choice.

In decent garden soil, lettuce rarely needs much feeding. Adding compost or well-rotted organic matter before planting is usually enough.

Container plants eventually exhaust what's available to them, so an occasional general-purpose liquid feed can help if growth begins to slow.

Don't overdo it, though. Lettuce grows quickly by nature. Give it reasonable soil, enough moisture and room for its roots and it'll usually get on perfectly well without being fussed over.

Harvesting

The lovely thing about lettuce is that you can harvest it at almost any stage.

For loose-leaf varieties, start picking once the plants have produced a useful amount of foliage. Take a few of the larger outside leaves and leave the centre alone. The plant will carry on producing fresh growth, giving you several harvests from the same lettuce.

If you're growing a variety that forms a proper head, wait until it feels nicely filled out and cut the whole plant at soil level.

I wouldn't leave mature lettuces hanging around simply because they could become slightly bigger. Young lettuce is usually sweeter and more tender, and warm weather can turn a perfect lettuce into a bolting one surprisingly quickly.

Harvest in the morning if you can, when the leaves are cool and crisp.

And only pick what you need. One of the great luxuries of growing lettuce at home is leaving tomorrow's salad alive in the garden rather than slowly wilting in the fridge.

Common Problems

Slugs and snails are probably the biggest nuisance. Unfortunately, a young lettuce seems to be their idea of fine dining. Check around plants in the evening and look underneath pots, boards and other hiding places nearby. Protecting seedlings while they're small is particularly worthwhile — an established lettuce can survive a few nibbles, while a tiny seedling can disappear overnight.

Bolting is another common frustration. The plant suddenly stretches upwards, becomes tougher and prepares to flower. Hot weather, dry soil and other stresses can encourage it. Keep plants watered, choose bolt-resistant varieties for summer and use a little afternoon shade during very hot spells. Most importantly, keep sowing small batches so another crop is always coming along.

Aphids can gather around tender leaves and deep inside developing heads. Check plants regularly and deal with them early. A strong but careful spray of water will often dislodge small colonies.

Poor germination in summer can simply be down to heat. Lettuce seed prefers cooler conditions than many people realise, so move seed trays out of a roasting greenhouse and germinate them somewhere cooler.

You may also see rotting lower leaves, particularly when plants are crowded or conditions stay damp. Give lettuces enough space, improve airflow and remove leaves that are lying against wet soil.

Finally, don't worry about a few holes. Home-grown lettuce rarely looks as cosmetically perfect as a supermarket bag, and that's fine. Wash it, remove anything particularly chewed and enjoy the rest.