Crop type: Lettuce
Lactuca sativa ‘Winter Density’ (Cos Lettuce Group)
Common name: Cos lettuce ‘Winter Density’ AGM
Crop slug: lettuce
This Allotment Pro editorial draft summarises the cited RHS cultivar profile. Check the source and adjust cultivation decisions for local conditions.RHS cultivar profile
1 - Overview
‘Winter Density’ is a compact semi-cos lettuce grown for crisp, tightly packed hearts. The low heart is wrapped by protective outer leaves, giving the mature plant a sturdy, close-set appearance that sits between a small cos and a compact butterhead.
Its useful distinguishing traits are good winter hardiness and resistance to bolting. Sow in autumn for an early-spring harvest, when its ability to tolerate cool conditions extends the lettuce season beyond the usual summer crop. The RHS Award of Garden Merit marks it as a dependable garden cultivar when grown in suitable conditions.
2 - Size
- Ultimate height
- 0.1–0.5 metre
- Ultimate spread
- 0.1–0.5 metre
- Time to ultimate size
- 1 year
Plants remain compact at harvest, but adequate spacing is still important so each low heart can fill without crowding. Its small footprint also makes it useful in raised beds and protected containers.
3 - Growing conditions
- Suitable soils
- Chalk, clay, loam or sand
- Moisture
- Moist but well-drained
- Soil pH
- Acid, neutral or alkaline
Use fertile, moisture-retentive soil that drains freely. Lettuce roots are shallow, so keep moisture even throughout heart formation and avoid alternating drought with heavy watering. Incorporating mature organic matter before sowing or planting helps provide both fertility and reliable water retention.
4 - Position and hardiness
- Light
- Full sun
- Aspect
- South- or east-facing
- Exposure
- Sheltered
- Hardiness
- H2 — tolerant of low temperatures but not surviving prolonged freezing
A sunny, sheltered position supports steady growth through the cooler months. Although ‘Winter Density’ has useful winter hardiness, protect autumn and early-spring plants with cloches, fleece or a cold frame during severe conditions. Ventilate covers on mild days to reduce stagnant humidity.
5 - Colour and seasonal interest
The plant forms a compact rosette of fresh green outer leaves around a paler, crisp heart. Leaves are upright to slightly cupped, smooth and close packed rather than deeply lobed or frilled. Its main season of interest is the cool growing period from autumn into early spring. Lettuce is harvested before flowering, so a normal crop should not carry blooms or seed heads.
6 - Botanical details
- Family
- Asteraceae
- Native to Great Britain and Ireland
- No
- Foliage
- Deciduous
- Habit
- Clump forming
- Name status
- Accepted
Genus
Lactuca includes annuals, biennials and perennials with milky sap and alternate leaves. Lettuce cultivars are selected for edible leaves and hearts and are normally harvested before the flowering stem develops.
Safety
No specific handling warning is listed on the exact RHS profile. Wash leaves thoroughly, discard damaged or decaying material and follow normal food-hygiene practice before serving.
7 - How to grow
Cultivation
Grow in full sun in fertile soil that holds moisture without becoming waterlogged. Sow the autumn crop thinly and protect it as temperatures fall. Thin seedlings early to prevent crowding, maintain even moisture and keep the bed weed free by shallow hand cultivation that does not disturb the roots.
Use cloches or fleece to protect plants at the beginning and end of the season. Water at soil level, preferably in the morning, so leaves do not remain wet overnight. Harvest once the compact heart feels firm but before it elongates or begins to bolt.
Propagation
Propagate by seed. Sow a small quantity at a time for manageable harvests and avoid sowing into hot, dry soil, which can inhibit lettuce germination.
Suggested locations
- Sheltered vegetable plot
- Raised bed
- Cold frame or unheated greenhouse border
- Container at least 30cm wide and deep
Pruning
No pruning is required. Remove yellow or damaged outer leaves and harvest the complete head at maturity.
Pests
May be susceptible to slugs, snails and root aphids. Inspect beneath the low outer leaves, keep the immediate area free of debris and use suitable barriers or biological controls where necessary.
Diseases
May be susceptible to grey mould and lettuce downy mildew. Provide ventilation beneath protection, avoid crowding, water early at soil level and remove affected plants or leaves promptly.