Last edited by shiny on November 07, 2026. View history
Cos Lettuce
A variety of lettuce
How to sow cos lettuce: Direct seed outdoors, thin to 20cm when seedlings are 3cm tall
Sun requirement for cos lettuce: Plant in Partial Sun
Lettuce is a cool weather crop and high temperatures will impede germination and/or cause the plant to bolt (go to seed quickly). Some hybrid cultivars have been bred to be more heat-resistant.
- 5
- plantings
- 2
- harvests
- 0
- seed packets
Cos lettuce facts
Lifespan
Grown for
leaf harvested 2 timesCrop cycle
Max altitude
Optimal light
What are growing degree days?
A plant grows with warmth, not with days. A growing degree day is one day's worth of useful warmth: how many degrees the day's average temperature is above the lowest temperature the crop grows at. Add them up from planting and you know how far along the crop is, whatever the calendar says.
Say that lowest temperature is 10°C. A day averaging 17°C gives 7 growing degree days. A day averaging 8°C gives none, as it is too cold for the crop to grow. That is why the same lettuce takes about 50 days in a summer and 90 in an autumn: it needs the same total warmth either way.
For cos lettuce, the FAO EcoCrop database gives a lowest growing temperature of 5°C and a shortest growing cycle of 35 days at its best temperature, about 403 growing degree days to a first harvest.
Where you've told us where your garden is, we use this and the weather there to predict when your cos lettuce will be ready to harvest. We don't use it for how long a plant lives or when it finishes: we go by what members have logged for that.
Growing cos lettuces
deterring pests
- place tilted jars of yeast+warm water (or beer) as slug traps at planting out every month
Growing lettuce
- Sow seeds in trays 3 weeks before planting out
- Dig compost into the bed 1 week before planting out
- Water regularly at planting out every week
- Weed around the seedlings 2 weeks after planting out
- Sow another batch for a continuous harvest 4 weeks after planting out every month
- Start picking the outer leaves at first harvest
- Pull out plants that have bolted 6 weeks after first harvest
How members grow cos lettuces
Sunniness
Planted from
Harvested for
Plant cos lettuces with
bell pepper
spring onion
elephant garlic
bonnie bell sweet pepper sfg
Photos
Photos
Cos lettuce plantings
Video
Where cos lettuces grow
Only plantings by members who have set their locations are shown.
What people are saying about cos lettuces
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Who's planted cos lettuces
- shiny The Deck · Wellington, NZ
shiny
Cos lettuce harvests
-
shiny harvested 3.
almost 2 years ago
-
shiny harvested not specified.
almost 9 years ago
shiny harvested 3.
Find cos lettuce seeds
There are no seeds available to trade on Growstuff right now.
- Purchase seeds via Ebay
- Sign in or sign up to list your seeds to trade.
Time to harvest
If sown now, expect a first harvest in about 35 to 85 days.
From the growing cycle in the FAO EcoCrop database, which is the same wherever it is grown.
Ecological requirements
Data from the FAO EcoCrop database for Lactuca sativa var. capitata L.
| Family / Taxonomy | Magnoliopsida Asteridae Asterales Compositae |
|---|---|
| Killing temperature | growth: 0 °C, rest: -1 °C |
| Life form | herb |
| Life span | annual, biennial |
| Habit | acaulescent (or rosette plants) |
| Optimal soil depth | shallow (20-50 cm) |
| Optimal soil texture | medium, light |
| Optimal soil fertility | moderate |
| Optimal soil drainage | well (dry spells) |
| Optimal soil salinity | low (<4 dS/m) |
| Photoperiod | short day (<12 hours), neutral day (12-14 hours) |
Learn more about cos lettuces
Resources outside Growstuff.
