Lettuce Winter Density is best described as having the best qualities of both a butterhead and romaine. It is an extremely early Semi- Cos lettuce that produces good yields of 20 to 25cm (8 to 10in) dark green, slightly savoyed leaves with a sweet succulent flavour.

This dwarf, compact variety with dark hearts, rather like a large Little Gem, is famously slow to bolt in summer and yet quite frost resistant, it is one of the hardiest varieties available.
It is very popular for autumn sowing and can be grown all year round in cooler climates. It can also be sown directly outdoors in spring and early summer. Matures in 65 days

Winter Density are usually grown to full size before harvesting, but is becoming more popular for baby or young leaf use. It is a favourite of Mesclun growers and can frequently be found in their mixes.

• Recommended by the National Institute of Agricultural Botany.
• RHS Award of Garden Merit winner.

Prepare the site:
A rich soil is excellent for lettuce, but the crop will also do well in average garden soil. The best crops are grown in soil that is deeply enriched with well-rotted manure and is well-fertilized before planting, especially with high nitrogen--leaf-stimulating--fertilizers such as 10-8-4, cottonseed meal, or blood meal. Lettuce doesn't do well in very acidic soils, and some say the pH shouldn't be lower than 6.5.

Timing:
Lettuce is about 95 percent water. It develops rapidly if the growing season is cool and moist. It can grow from seed to salad in about 1 month in many regions, and only a little longer in others. Lettuce is a cool-season vegetable, with an ideal temperature of 10-16°C (50-60°F); it does poorly in hot weather, and is tolerant to some frost and light freezes. Cos is more heat tolerant than most. The secret of having salad leaves in spring is to sow them in late summer and the New Year, the first to overwinter and the second to provide an in-between harvest before the spring sowings become big enough to pick.

Sowing:
Sow indoors under protection: Sept to Mar or sow directly outdoors: Mar to Aug
Lettuce germinate at surprisingly low temperatures The perfect temperature for germination is 4 to 16°C (40-60°F) rates decline above 20°C (68°F). The perfect temperature for growth is 16-18°C (60-65°F)
Sow at a seed depth of 6 to 12mm (¼-½in) Seed will germinate in 7 to 14 days.

Sow seeds in short rows about 30cm (12in) apart. To do this, make a shallow trench with a cane about 1.5cm (½in) deep. Space the rows 20cm (8in) apart.
If you are sowing directly into the soil, (if you do not have a problem with slugs!), water the drill before sowing to cool the soil down. A shaded part of the garden is ideal. If birds are a problem in your garden, spread netting to prevent them eating the seed.
Tip a small amount of seed into your hand, take a pinch and spread thinly along the trench. Cover with soil, label and water. When the seedlings are about 2cm (1in) tall, thin them out to give them space to grow, 15-20cm (6-8in). Replant or eat the seedlings. Make successional sowings at 14 day intervals.

Cultivation:
In summer, a mulch of grass clippings, salt hay, clean straw, or the like, will keep the weeds out and the growing soil moist and cool. The plants need almost constantly moist ground, watering is essential if rainfall is scant. This is particularly important when the lettuces are one or two weeks away from harvesting, as dry soil now will cause the plants to put their energy into producing flowers.
The key to tender and tasty lettuce is rapid growth, however lettuce has a relatively shallow and compact root system that doesn't absorb nutrients and moisture from the soil very efficiently, which can slow the growth. To encourage fast growth, add plenty of finished compost before planting and again as a side-dressing a week or so after seedlings appear or transplants are planted. Give supplemental feedings of compost tea every few weeks until harvest.

Pests:
Aphids – Wash off minor infestations before the plants are eaten. If there is a heavy population grow nasturtiums near the lettuce, or use an organic solution.

Harvesting:
60 days to maturity. Harvest all lettuce in early morning for the maximum carotene and best taste and refrigerate immediately. Harvest as soon as they are big enough for the salad bowl. The harvest is over when a central stem starts to form. This is the signal that the plant is getting ready to bolt and the leaves start to get bitter.

Rotation considerations:
Avoid following radicchio, endive, escarole or artichoke.

Good Companions:
All brassicas (except broccoli, but especially radishes), beat, carrot, cucumber, onion family, pole lima bean, strawberry

Bad Companions:
None

Nomenclature:
Native to Western Europe and the eastern Mediterranean area, it is called cos or cos lettuce (mainly with British-speaking peoples) because it is said to have originated on the Greek island of Cos (Kos), off the coast of Turkey in the Aegean Sea.

It has been cultivated and eaten cooked or raw for almost 5,000 years and may very well be the oldest form of cultivated lettuce. Egyptian tombs reveal paintings of lettuce with long, pointed leaves, resembling romaine. It was known to the Romans, who usually ate lettuce cooked, as Cappadocian lettuce, and was called Roman lettuce due to the Romans belief in its healthful and healing properties.
It is said that in the 14th century when the Popes of the Roman Catholic Church temporarily moved from Rome to Avignon, they brought this variety of lettuce with them, calling it Avignon lettuce. The earliest English name for it was Roman lettuce, around the 17th century. The source of the English romaine is from the French laitue romaine, Italians call it lattuga romana.

A white latex oozes from its leaf base and the thicker ribs of older, larger leaves and is reflected in its Latin name ‘Lactuca’, which means milk. Lettuce juice was used as a medicine by many ancient herbalists.
According to Pliny, the emperor Augustus Caesar is said to have put up a statue to honour its healing abilities after being cured of a serious illness.
See recipes for Caesar Salad for the ultimate use of this popular lettuce.