Tatsoi (Brassica rapa var. rosularis)
2 sources cited · Verified
The short answer
- Plant
- Mid March to late August
- Site
- 5+ hours of sun, soil pH 6–7.5
- Biggest risk
- Brassica downy mildew
In the UK, tatsois go in the ground mid March to late August.
Tatsois (Brassica rapa var. rosularis) — annual or biennial grown as an annual.
Timing is the decision that matters most in the UK: there are 4 separate regional sowing windows, ranging from mid March in Southern England to mid March in Scotland.
Core growing advice on this page is checked against named horticultural and university-extension sources — see References.
Regional Planting Calendar
| Region | Sow |
|---|---|
| Southern England | mid March to late August |
| Midlands | mid March to late August |
| Northern England | mid March to late August |
| Scotland | mid March to late August |
Southern England - detail & sources
GrowVeg gives a spring plus late-summer two-window pattern rather than UK-specific dates; a window spanning both is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Midlands - detail & sources
GrowVeg gives a spring plus late-summer two-window pattern rather than UK-specific dates; a window spanning both is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Northern England - detail & sources
GrowVeg gives a spring plus late-summer two-window pattern rather than UK-specific dates; a window spanning both is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Scotland - detail & sources
GrowVeg gives a spring plus late-summer two-window pattern rather than UK-specific dates; a window spanning both is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
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.
Diseases
Pests
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
When should I sow tatsois in the UK?
In Southern England, from mid March. In Scotland, wait until mid March. Treat these as a guide rather than a fixed date — the governing rule is to sow only once frost risk has passed and temperatures are reliably warm enough.
When do I sow tatsois?
Sow mid March to late August.
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
Most of the advice on this page comes down to timing and spacing — sowing at the right moment, rotating beds, and giving plants enough airflow. The UK Garden Planner lays your plot out month by month so those decisions are already made before the season starts.
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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.