Last edited on August 25, 2025. View history
Choy Sum
A variety of cabbage
How to sow choy sum: Direct seed outdoors
Sun requirement for choy sum: Plant in Partial Sun
Choy Sum, or Yau Choy, is a cool season vegetable in the Brassicaceae family. It has large flat leaves, slender stems, and tiny yellow flower buds. All parts of the plant can be eaten - leaves are added raw to salads, and the whole plant can be steamed or stir-fried. It's flavor is a cross between spinach and cabbage, and it is sometimes described as a milder, less bitter version of Broccoli Raab. Green varieties are not frost-tolerant, but purple ones can withstand temperatures below 0°C. It is sometimes called Yu Choi when harvested without flowers, and Yu Choi Sum when harvested with flowers.
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- seed packet
Choy sum facts
Lifespan
Height × spread
35cm × 35cmRow Spacing
15cmCrop 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 choy sum, the FAO EcoCrop database gives a lowest growing temperature of 7°C and a shortest growing cycle of 60 days at its best temperature, about 750 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 choy sum 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 choy sum
- Sow seeds in trays 5 weeks before planting out
- Dig compost into the bed 1 week before planting out
- Harden off the seedlings 1 week before planting out
- Firm the soil well around the stems at planting out
- Net against cabbage white butterflies at planting out
- Set or refill beer traps for slugs and snails at planting out every week
- Water regularly at planting out every week
- Check leaves for caterpillars 2 weeks after planting out every week
- Feed with a nitrogen fertiliser 4 weeks after planting out
- Cut heads once they feel firm at first harvest
- Pull out the stalks 4 weeks after first harvest
How members grow choy sum
Sunniness
Planted from
Plant choy sum with
bush bean
german chamomile
cumin
blue lake bean
Photos
Photos
Choy sum crops
Video
Where choy sum grow
Only plantings by members who have set their locations are shown.
What people are saying about choy sum
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Who's planted choy sum
- Skud Thornbury mini-greenhouses · Ballarat, Victoria,...
- juliet Back garden · London, UK
Choy sum harvests
Nobody has harvested this crop yet.
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Time to harvest
If sown now, expect a first harvest in about 60 to 200 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 Brassica oleracea var. capitata L. [Alef.]
| Family / Taxonomy | Magnoliopsida Dilleniidae Capparales Cruciferae |
|---|---|
| Killing temperature | growth: -1 °C, rest: -10 °C |
| Life form | herb |
| Life span | biennial |
| Habit | acaulescent (or rosette plants) |
| Optimal soil depth | shallow (20-50 cm) |
| Optimal soil texture | medium, organic |
| Optimal soil fertility | high |
| Optimal soil drainage | well (dry spells) |
| Optimal soil salinity | low (<4 dS/m) |
| Photoperiod | neutral day (12-14 hours), long day (>14 hours) |
Learn more about choy sum
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