Lettuce
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Overview:
There are basically four types of lettuce namely; Cos, Loose-leaf, Crisphead often referred to as Iceberg lettuce, and Butterhead, although many of these have now been crossed with each other to give a variety of lettuce types each with traits of the texture and colour of the parents.
Lettuce dislike hot conditions making them a suitable salad vegetable to grow in the variable summer weather of the UK.
They will bolt if the weather becomes too hot or if there is a shortage of water.
They are suited to most types of soil providing it remains moist but not water logged, and idealy it is not too rich in nutrients.
This attribute makes it a useful subject for growing as a follow on crop after a previous crop has been harvested.
Similarly they can be grown between slow growing vegetables that don't mature till late in the year.
Another advantage is in these situations some shade can be offered during the hottest parts of the day.
All one must remember is that the lettuce plants will be in competition for moisture with the adjacent plants so extra watering may be required.
Lettuce can take about 12-14 weeks from sowing to maturity.
With prudent sowings, and the use of various varieties, lettuce can be available for a large part of the year.
Lettuce is a shallow rooted plant, meaning it will require regular watering otherwise it will bolt or turn bitter.
Typical Growing Season
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Cultivation:
Week 1:
Check plants growing under cover for grey mould (botrytis) or slug damage.
Week 11:
To get an early spring crop, sow seeds in 75mm (3") pots, ¼ trays or cell trays filled with of potting compost to grow on undercover.
Temperatures need to be considered when sowing, too warm temperatures 21°C+(70°F+) can inhibit germination, and seeds can sit dormant or germinate erratically.
Germination should take about 4-5 days.
Week 13:
Thin out, or prick out seedlings into individual pots and place them in a frost free cold frame.
Week 18-19:
If conditions allow plant out seedlings 300mm (12") apart in rows 400mm (16") apart (avoid firming in too vigorously).
Sow seed insitu if soil conditions allow.
Lettuce will grow in most soil types, adding organic matter a few weeks prior to planting helps to retain moisture, a shortage of which can encourage premature bolting.
Planting out in light shade will also help.
Rake in a topdressing of a general fertiliser at 100gms (4oz) per sq metre when planting out.
Week 23:
Make successional sowings every two to three weeks to prolong the growing season.
Note: Lettuce seed should be stored in the fridge between sowings.
Water plants regularly in hot weather.
In hot, dry summers sowing may pose germination problems when sown in situ.
Try sowing in modular trays and transplant the plugs when two or three true leaves develop.
Week 37:
Sow a pinch of seeds of a hardy winter variety in 75mm (3") pots of proprietary potting compost.
Germination should take about one week to ten days.
Week 40:
Thin out, or prick out seedlings into individual pots and place them in a frost free cold frame.
Aternatively sow a couple of seeds in each module of a cell tray and thin seedlings to leave one, then place them in a cold frame.
Week 42:
Plant out seedlings into their final positions in greenhouse border, frames or under cloches.
Soil should be well-drained and given a light dressing of a balanced, general fertiliser at a rate of about 90/120gm (3-4oz) per sq m to get plants established before winter.