It’s increasingly difficult to find good quality, fresh lettuce in the supermarkets. Lettuce is easy to grow and with a little planning, you can eat it fresh for 9 months of the year.
There are four main types of lettuce. The first three - butterheads, cos and crispheads - form hearts at their centre and are therefore usually grown as proper heads of lettuce. They take longer to mature. The fourth type - loose-leaf - doesn’t form a heart and is therefore generally grown as a “cut-and-come-again” crop – where leaves are cut as required. Sow seeds in module trays – if you are growing heads of lettuce, sow just one seed in each module. With loose leaf types, sow 3-5 seeds per module. Lettuce needs light to germinate so don’t cover the seeds with compost. Lettuce will not germinate in temperatures above 25 degrees celsius so if the weather is warm you may need to move the trays in to cool shed for a few days until they germinate. Seedlings are ready to plant out when they have 4 or 5 leaves. Harden off well before transplanting.
Lettuce will do well in any reasonable soil, as long as it’s moisture retentive – add well-rotted manure or compost the previous winter. Lettuce is a great space filler – you can pop it anywhere you have some space. Spacing is about 20-30cm depending on the type. Plant the seedlings well down in the soil with the cotyledons (seed leaves) just above the soil level. Keep the soil around the plants weed free and water copiously in dry weather – this will help prevent them bolting. Use fleece or cloches to protect early sowings from frost.
Cos, Butterhead and Crisphead varieties of lettuce need to be left longer to develop their hearts. Cut leaves of loose-leaf varieties as soon as they are of usable size. If you cut them about 5cm from the ground they will grow back and you will be able to take a second crop in a few weeks. Harvest lettuce leaves early in the day and they will keep far longer. This is because later in the day the moisture has evaporated from the leaves and so it wilts more quickly.
Lack of water causes the plants to panic and run to seed in a desperate attempt to reproduce before they die! This is called “bolting” and it’s very bad news as the plants are too bitter to eat. Slugs eat young leaves and get in to the hearts of lettuces. Aphids (black or greenfly) can be a problem. Leatherjackets (the larvae of the Daddy Longlegs) eat through the stems of newly planted lettuce.