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A picture of a Cos Lettuce

Cos Lettuce

Lactuca sativa var. longifolia 'Cos'

Also known as

Romaine Lettuce, Cut And Come Again Lettuce

Partial Shade
Easy care
Moderate watering
Tender

H1a

RHS hardiness

15°C

Minimum temperature

Expected size

Height
Spread

30cm

Max

25cm

20cm

Min

15cm

Flowering

  • spring
  • summer
  • autumn
  • winter

This plant has no fragrance

More images of Cos Lettuce

A photo of Cos Lettuce
A photo of Cos Lettuce

Cos Lettuce Overview

Cos or Romaine lettuce grows with a more upright or oval head shape, has sturdy leaves with firm ribs down their centres with dark outer leaves, slightly bitter taste and a crispy texture. It is considered to be more nutritious than crisphead lettuce and is usually the lettuce used in a Caesar salad.

Common problems with Cos Lettuce

Slugs and snails feed on the leaves, control with organic snail bait or beer traps. Aphids may be a problem, encourage beneficial predators like lady bugs and spray organic insecticide when predators are not present.

Cos Lettuce Companion Plants

How to harvest Cos Lettuce

Leaves are harvested individually or as a whole plant. The plant is ready to harvest 60 to 70 days after planting. Harvest before a central stem forms. If temperatures are too high the plant will bolt forming a central stem with flowers and eventually seeds.

How to propagate Cos Lettuce

Seed

Sow seeds in seed trays at a depth of 0.6 to 1.3cm. The optimal temperature for germination is around 20 °C. Transplant after 4 to 6 weeks.

Cuttings

If the whole plant is harvested and the base of the plant is kept in a bowl of water, the centre of the plant will continue to grow and form new leaves.

Special features of Cos Lettuce

Crop rotation

To prevent soil diseases, follow lettuce planting with dwarf beans, carrots, cucumbers, squash or basil.

Pot plant

Indoor plant

Popular to grow in greenhouses or tunnels.

Wet sites

Salads are easily to grow in a hydroponic set-up.

Other uses of Cos Lettuce

Edible

Leaves are eaten mostly raw, but can be cooked too.