Growing Lettuce in Scotland: The Complete Guide

Lactuca sativa

Everything you need to grow lettuce in Scotland, from the first March sowing to a winter variety standing through the cold months for a spring harvest. We have done the research so you don't have to.

Lettuce is one of the few crops where Scotland's climate actively helps rather than hinders. It bolts, runs to flower and turns bitter, in hot, dry weather. It also refuses to germinate once temperatures climb too high. Further south both of those are summer problems that narrow the growing window. Here, our cool summers keep the window open, and successional sowing from spring into late summer works more reliably than it does almost anywhere else in Britain.

Why Scotland suits lettuce

Lettuce wants it cool. That is the simplest way to understand this crop, and it explains nearly everything that goes wrong with it. Hot dry weather triggers premature flowering, which makes the leaves bitter and ends the crop. High summer temperatures can stop some varieties germinating altogether. In much of England these are the limiting factors that squeeze the season between spring and late summer.

In Scotland neither is a typical summer problem. The practical effect is that succession sowing, a short row every fortnight, genuinely works here from late March through to July, and a July sowing will still be producing in September when an English equivalent would have bolted weeks earlier. The trick is not to sow everything at once.

Types: loose-leaf or hearting

Lettuce types differ more than most people expect, and the choice settles how you harvest and how long the plant earns its space.

• Loose-leaf types do not form a heart. You pick a few outer leaves at a time, and the plant keeps producing new ones from the centre. They are ready in as little as four to six weeks. A dozen loose-leaf lettuces picked this way will feed a household for weeks rather than days.
• Hearting types come in three kinds: Butterhead, Cos and Crisphead. They form a dense central head and are cut whole. They take longer, around ten to fourteen weeks. Cut through the stem leaving a stump about 2.5cm tall, and it should re-sprout at least one more crop. The payoff is texture. A crisp Cos heart is worth the wait. Among hearting types, Crisphead and Cos are more resistant to bolting.
• Winter varieties are sown in September or October and stand through the cold months to crop in spring. They will not grow much over the darkest weeks, but they will hold, and a March lettuce from your own garden is one of the most satisfying things a Scottish grower can produce.

If you only grow one type, loose-leaf gives you the longest harvest from the fewest plants. A row of loose-leaf sown in succession, plus a winter variety to bridge the hungry gap, covers nearly the whole year except the darkest months.

Varieties

The type decision above matters more than the variety name. These carry the RHS Award of Garden Merit, a UK-wide award rather than a Scottish one.

Also worth considering

Soil and site

Lettuce wants fertile, moisture-retentive soil in a sunny spot. If you are sowing in mid-summer, a little light shade during the hottest part of the day is actually better. Too much heat can trigger bolting. Dig in plenty of garden compost before sowing to help retain moisture, and rake the bed level because the seed is small and shallow-sown.

The real requirement is steady moisture. Lettuce has shallow roots and will not forgive a dry spell during warm weather. The bed that stays damp is the one that produces the best crop, and in Scotland that is more often a matter of choosing a spot that holds water rather than one that sheds it.

Sowing

Sow outdoors from late March to late July for summer and autumn harvests. Sow about 1cm deep in rows about 30cm apart, and thin gradually to 15cm to 30cm apart depending on type. Loose-leaf types can be closer, hearting types need the full spacing to form a firm head. The thinnings are perfectly good to eat as baby leaves.

The rule is succession, not volume. Sow a short row every fortnight rather than one long one. A March sowing gives you the first pickings in May. A July sowing is still worth doing here, because the cool late summer will carry it into September and October without bolting. In a hot spell, sow in the evening once temperatures have dropped, and water the drill with cold water beforehand.

For an early start, sow indoors in early February, prick out into modules, and plant out in early March under cloches or fleece. That buys you the earliest lettuce of the year and keeps the seedlings safe from slugs while they are small.

Winter varieties are a different calendar: sow in September or October in a greenhouse, or outdoors under cloches in mild areas. Give them the best-drained, sunniest spot you have, because cold and wet together will kill them where cold alone will not.

Planting out

Young plants raised indoors or bought as plugs go out from spring onwards. Harden them off first. Space hearting types about 30cm apart. Too close and they will not form good hearts. Space loose-leaf types about 15cm apart. Lettuce plants take up very little room and can be tucked into gaps between slower crops like parsnips or sweetcorn, because they will be harvested before the main crop needs the space.

In spring and in colder regions, plants establish faster under cloches or fleece. Protect from slugs and snails, especially in damp weather. Early in the year birds will go for young lettuce plants too. A net or fleece is a simple fix.

Containers: lettuces grow well in pots. Use a container at least 30cm wide filled with peat-free multipurpose compost. Space the plants as above. Compost in pots dries out faster than soil, so check regularly in summer.

Watering and care

Lettuce is shallow-rooted and needs steady moisture. This is the job that earns the crop. A dry week during warm weather is the single most common cause of bolting, and once a lettuce has bolted you cannot rescue it. The best time to water is early in the morning. It sets the plants up for the day, and watering in the evening leaves the soil damp all night, which attracts slugs and encourages grey mould.

Once plants are established, a thick mulch of garden compost around them holds moisture and keeps the weeds down. Lettuce does not usually need feeding in the ground. Container plants benefit from a general-purpose organic liquid feed every fortnight through summer.

Weeding matters because lettuce cannot compete with anything that germinates next to it. Dense weeds also give slugs a place to hide and reduce air circulation, which encourages fungal problems.

The slugs, and what to do about them

Slugs are the dominant lettuce problem in a wet climate. Four things genuinely help.

• Start plants in modules. A sturdy transplant with a few true leaves can shrug off a slug attack that would wipe out a row of seedlings.
• Keep the area clear. Slugs hide in long grass, weeds and debris. A tidy bed with bare soil gives them nowhere to shelter during the day.
• Water in the morning. Wet soil at night is an invitation. Watering early lets the surface dry before the slugs come out.
• Accept some loss. A few slug-holed outer leaves on a loose-leaf lettuce will go unnoticed in the salad bowl. Tolerance is a realistic strategy in a wet country.

Harvesting

Loose-leaf types are ready about four to six weeks after sowing. Pick a few outer leaves from each plant rather than cutting the whole thing, and it will keep producing for weeks. Hearting types take about ten to fourteen weeks. Once a firm heart has formed, cut through the stem leaving a short stump about 2.5cm tall. It should re-sprout and give you at least one more smaller harvest.

Pick in the morning, when the leaves are crisp and full of moisture. A lettuce cut in the heat of the afternoon wilts within the hour. If you are not eating it straight away, stand the whole head in a bowl of cold water for ten minutes. It comes back to life. Winter varieties sit through the coldest months and start growing again as the days lengthen. The first proper harvest of the year, in March or April, is worth the bed space all winter.

Common problems

• Bolting. The plant shoots up tall and turns bitter. Caused by hot dry weather, and far less of a problem in Scotland than further south. Watering steadily through a warm spell and a little shade reduce the risk. Once it has happened, pull the plant and compost it.
• Slugs and snails. The main lettuce problem in a wet climate, covered above. Module-raised plants are the single best defence.
• Aphids can colonise lettuce, particularly under cover. They rarely kill the plant, and washing the leaves at harvest removes them.
• Grey mould (botrytis). A grey fluffy mould, usually in cool humid summers. Good spacing, keeping water off the leaves, and watering in the morning all reduce the risk.
• Nothing coming up in a warm spell. The soil is too hot. Lettuce seed goes dormant at high temperatures, which is rarely an issue in Scotland but can happen during a July heatwave. Sow in the evening, water the drill with cold water beforehand, and provide some shade.

Common questions

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