Tatsoi (Brassica rapa var. rosularis)
2 sources cited · Verified
The short answer
- Site
- 5+ hours of sun, soil pH 6–7.5
- Biggest risk
- Brassica downy mildew
Tatsois (Brassica rapa var. rosularis) — annual or biennial grown as an annual.
This crop carries an unusually heavy problem load: 3 diseases, 5 pests and 0 nutrient issues are documented for it, so most of the effort in growing it well goes into prevention.
Core growing advice on this page is checked against named horticultural and university-extension sources — see References.
Diseases
Pests
Quick Facts
| Factor | Value |
|---|---|
| Soil pH | 6 - 7.5 |
| Sunlight | 5-5 hours direct sun |
| Soil texture | chalk, clay, loam or sand, deep and fertile but firm (RHS) |
| Drainage | well-drained |
| Lifecycle | annual or biennial grown as an annual |
| Edible parts | leaves |
At a Glance
Soil & Growing Conditions
Water: regular watering during summer months essential (RHS)
Soil pH range
Span reflects genuine variation between the cited authorities, not a single agreed figure.
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Sowing | 0 | Sow outdoors, seeds 2in apart barely covered with soil, or start in modules; germinates in 4-8 days at 50-80F. Sow in spring and again in late summer for a fall harvest (GrowVeg). |
| Thinning/transplanting | 3 | Thin gradually to 8in apart, or transplant module-raised seedlings once they have 5-6 leaves (RHS, GrowVeg). |
| Rosette formation | 4 | Flat, tight rosette of spoon-shaped, glossy dark green leaves develops; regular watering essential in summer (RHS). |
| Harvest | 8 | Harvestable in 45-50 days; cool weather and a light frost once mature improve flavour, while cold exposure when young risks early bolting (GrowVeg). |
Harvest & Storage
When to pick: Reaches harvestable size in 45-50 days (GrowVeg). Whole rosette can be cut, or individual outer leaves picked while the plant regrows. A light frost once mature is said to improve flavour.
Tatsoi, Rosette to Market
References
-
Sow in spring and again in late summer for a fall harvest. Plant seeds 2in (5cm) apart, barely covered with soil, thinning gradually to 8in (20cm) apart. Germinates in 4-8 days at 50-80F. Tolerates light frost, but cold exposure in spring can trigger early bolting; light frost in autumn is said to improve flavour. Reaches harvestable size in 45-50 days and can withstand temperatures down to -10C (15F).
-
Tatsoi has spoon-shaped, waxy, green leaves in a densely leaved, tight rosette; RHS files it as "rosette pak choi." Hardiness H5 (hardy in most UK locations even during severe winters). Full sun; works in all aspects (east, north, south or west-facing). Soil: chalk, clay, loam or sand; moist but well-drained; alkaline or neutral pH. Height and spread 0.1-0.5m. Time to maturity 1 year. Sow outdoors in deep, fertile but firm soil that isn't too acidic, or start in modules/seedtrays and transplant once seedlings have about 5-6 leaves; regular watering during summer months is essential. Propagate by seed. No pruning required; suitable for container and patio growing. PESTS: vulnerable to flea beetles (especially threatening seedlings), caterpillars from butterfly eggs, pigeon damage (netting required), snails, cabbage root fly, mealy cabbage aphids. DISEASES: susceptible to brassica downy mildew, white blister, and club root (particularly in previously cultivated brassica beds) -- named directly for this variety, not inferred.
2 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.
Frequently Asked Questions
What soil pH do tatsois need?
A pH of about 6–7.5. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.
What problems affect tatsois?
Our data links 3 diseases and 5 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
Almost everything on this page resolves to your own frost dates rather than the calendar — the last spring frost moves by roughly two months between zone 3 and zone 10. The USA Garden Planner works from your zone so the timing is already decided before the season starts.
Get the USA Garden Planner →Instant PDF download · Written for US growing conditions
Last verified 2026-08-29
Where To Go From Here
Take this crop from reading into a written plan for your own beds.
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.