How to grow lettuce from seed
Lettuces fall into three groups—cabbage, cos and loose-leaf. The cabbage
kinds are subdivided into crispheads and butterheads. Those sold by the greengrocer are almost always butterheads
because crispheads do not travel well and wilt rather quickly after harvesting. The cos varieties have long, boat-shaped, very crisp leaves and they are preferred by many for their fine flavor. Loose-leaf lettuces are more popular in the United States than here, although one American variety, 'Salad Bowl', is liked by many gardeners.
Any check to steady growth is liable to result in rather poor lettuces. Water is very important, but the soil must be sufficiently porous to allow for good drainage. Although late summer lettuces will tolerate the shade cast by rows of taller vegetables, earlier sowings demand an open, unshaded site. The soil should have been dug well during the winter digging programme and organic manures in the form of farmyard manure, garden compost or spent hops applied generously. These manures are invaluable in helping to retain soil moisture. If he is able to have use of greenhouse cold frames and cloches, the good gardener is able to raise lettuces for at least six months of the year. The production of winter and early spring lettuces is not easy and these crops are a challenge to the gardener. Certain hardy varieties for April cutting may be over-wintered in the open in favourable areas, but much depends on the winter weather following the autumn sowing.
Outdoor sowings may be made in March in the south-west and during the first two weeks of April in other areas. Here again, cloches are useful. Sow as thinly as possible in 2.5cm (1in) deep drills spaced 40cm (15in) apart. Keep down weeds by hoeing and thin the seedlings to 30cm (1ft) apart when three or four leaves have formed. The thinnings from March, April and May sowings may be used to make further
A sowing made in late July provides lettuces in November and December but here again, the weather plays an important part. The rows need cloche protection from October onwards. For early spring supplies, sow in the cold frame in September and, subsequently, replant the seedlings in the greenhouse or in frames. Alternatively, sow in the greenhouse in early October and transplant when the plants have four leaves. Deep planting at any time is unwise. It is particularly dangerous where lettuces are to be over-wintered. Over-crowding must also be avoided and correct ventilation is very important.
Birds often peck at lettuce seedlings and plants. A few strands of black cotton fixed above the rows prevents this trouble. Although present-day cos varieties are reputed to be self folding, better hearts form if the plants are tied rather loosely with raffia or soft string. Loose-leaf varieties are less prone to bolt than cabbage and cos plants. Instead of cutting the whole plant, leaves are picked as and when required from loose-leaf varieties.
Among the very many varieties on offer, the following may be relied upon for worthwhile crops.
For outdoor sowings from March until July 'Sutton's Improved', 'Unrivalled', Trocadero' , 'Webb's Wonderful', 'Giant White Cos', 'Salad Bowl'. To stand the winter out of doors 'Stan-stead Park', 'Arctic King', 'Brown Cos'