If you haven’t tasted the luscious, freshly-picked leaves of homegrown lettuce, then you’ve really been missing out! Lettuce can offer you the freshest leaves for picking almost year-round. It’s a really great crop for beginner gardeners, but for the healthiest plants there a few essential points you’ll need to bear in mind.
If you’re looking to up your lettuce-growing game you’re in the right place, because here are some top tips for growing perfect lettuce every time…
Sowing and Planting Lettuce
Lettuce is a cool-season crop, which means they fare best in cooler, more temperate conditions. Get on and sow them nice and early!
Moisture-retentive, fertile soil is ideal. You can improve your soil by simply adding plenty of organic matter such as compost to the soil in the weeks before sowing.
Sow outside up to four weeks before your last frost. For an earlier start, sow them on your sunniest windowsill or in a greenhouse, polytunnel or cold frame. For the very earliest sowings, when there simply isn’t enough natural light to give your seedlings the energy to grow, try starting them off under growlights before moving them out to your cold frame or greenhouse towards the end of winter.
Multi-purpose potting mix is fine for sowing. Sow several seeds into small pots, then transplant the seedlings into their own pots or plugs once they’ve germinated. Alternatively, sow two seeds per plug in a plug tray. Cover them over with about a quarter inch (0.5cm) layer of potting mix, perlite or vermiculite. Gently firm the potting mix down and water it.
Once the seeds have germinated and are big enough to handle, transplant them carefully into their own individual pots or plugs of potting mix. Make a hole in the potting mix deep enough for the roots, then carefully ease the seedlings out of their pot, handling them by a leaf to avoid crushing the delicate stem. Try to retain as much potting mix around the roots as possible. Feed the roots down into the potting mix in the new pot. They can be planted up to just below their first leaves. Firm the potting mix gently around them.
If you’re growing in plugs, just use scissors to snip out the weaker of the two seedlings – these won’t need to be transplanted until the roots have filled the plugs.
Once the roots have filled the pot or plug, you either need to pot them on again or think about transplanting them outside. You can help along transplants at the start of the season by covering them with a temporary cloche made from bottomless milk cartons or plastic bottles, or with row covers. These will keep the chill off your seedlings just enough to help them acclimatise.
Continue sowing every few weeks to enjoy a steady stream of leaves – I suggest small sowings each time, so you’re not overwhelmed! Carry on sowing for as long as conditions allow. The big issue when it comes to lettuces is heat – more on that below.
'Bolting' is the fancy name for when vegetables flower prematurely, before you’ve had a chance to harvest them. In most cases bolting renders the crop inedible, and that’s certainly the case for lettuces, whose leaves turn tough as they produce a truly wince-inducing, bitter milky sap. At this point plants are only good for pulling up and adding to the compost pile.
Bolting happens all too quickly in hot, dry weather, which this cool-season crop simply cannot stand. Keep your lettuce well hydrated by watering often to keep the soil moist. In hot climates you may need to rig up some shade cloth, or grow lettuces in the shadow of taller crops such as corn, pole beans or tomatoes. Remove weeds, so there’s as little competition for moisture as possible.
Hot weather can also cause erratic germination. There are two ways around this: germinate your seeds indoors (especially in air-conditioned properties in hot climates) or – my method – sow into pre-wetted drills: make your drill, water along it, let it drain then water again, before sowing your seeds and covering over. That way you’ve got a nice, cool, damp cushion around your seeds to help them germinate.
Combat Lettuce Pests
Lettuce is generally pretty trouble free, but there are two arch nemeses that might just hamper your efforts if they’re allowed to get away with it: slugs and aphids.
The simplest way to deal with slugs is to set up slug traps. Simply sink a shallow tray or pot into the ground, with the lip just above soil level, and then fill it up with beer. Any cheap beer will do – it doesn’t even have to be alcoholic – slugs love the stuff! They drown in the beer, but probably die happy. You’ll need to inspect, empty and refill your slugs trap regularly to help reduce the local slug population.
Other ways to reduce problems with slugs is to make sure plants and properly space, and remove weeds and lying debris so there are fewer hiding places. Pick off and remove slugs from regular lurking places.
Aphids are a common sight in early summer. The best way to make a dent on the aphid population is to attract their predators. That’s hungry bugs like hoverflies, lacewings, ladybirds, and a myriad of tiny, non-stinging parasitic wasps. Try growing calendula, poached egg plant, and zinnias. One of the best plants to attract beneficial bugs is sweet alyssum, a pretty, sweet-perfumed annual that can be planted among your lettuces to dramatically reduce problems with aphids. Why? Because alyssum is irresistible to the parasitic wasps that gorge on them!
Now when it comes to harvesting you’ve got two types of lettuce: loose-leaf lettuces that don’t form a tight, close-knit head, and head-forming lettuces that do. Each requires a slightly different harvesting technique.
Loose-leaf lettuces can be harvested in one go, by cutting them off at the base, but perhaps a smarter way to harvest these types of lettuce is to cut off one leaf at a time. Just pinch off the outer leaves at the base, close to the stem, between your finger and thumb. Leave the central leaves to grow on for your next harvest.
Head-forming lettuces – that’s lettuces like Romaine and iceberg types – can be harvested all in one go. But a little tip is to harvest a few of the outer leaves young, as baby leaves, before leaving the lettuce to grow on and produce that delicious, fulsome head. Don’t leave heading lettuces too long – it will only lead to tired, bitter leaves, as if the plant has bolted.
Get your harvested leaves into a bucket or sink of water as soon as possible after harvesting. This serves two purposes. It washes the leaves so that any residual bits of soil or grit and pests can be washed off, and it will delay wilting, especially in hot weather. Leave them in the water for at least five minutes then lift them out, rinsing as you go. You can gather the leaves between your hands to flick them dry or – easier – use a salad spinner. The cleaned leaves can then be kept in plastic bags in the refrigerator and will stay in good condition for a few days.
I’m going to be growing Romaine-type lettuces this year – just the business for a satisfying salad – as well as some ‘Salad Bowl’ loose-leaf lettuces, which almost grow like weeds! What sorts of lettuce will you be growing? Share all in the comments below.