Tatsoi
Brassica rapa subsp. narinosa
Also known as: Spoon mustard, Spinach mustard, Rosette pak choi, Tat soi, Tah tsai
Quick facts
- Category
- leafy greens
- Difficulty
- beginner
- Days to harvest
- 30 to 50 days
- Harvest type
- cut leaves, plant regrows for repeated harvests
- Spacing
- 20 cm between plants
Environment
- Temperature
- 4–24°C
- pH
- 6 to 7
- EC (hydroponic)
- 1.2 to 2 mS/cm
- Daily light
- 12 to 17 mol/m²/day
Climate and zones
- USDA zones
- 3 to 10 (winter low around -40°C or warmer)
- Frost tolerance
- very hardy (survives deep cold)
- Season
- cool (spring and fall crops)
Viable growing environments:
- outdoor year-round (in zone)
- outdoor in growing season (annual)
- unheated greenhouse / hoop house
- heated greenhouse
- indoor (heated home)
- indoor hydroponics under grow lights
USDA zone bounds reflect outdoor year-round survival. Anywhere outside the bounded zone range, this crop still grows as an annual in the warm months (outdoor_seasonal), under cover (greenhouse), or indoors under lights.
Growing systems
Tatsoi works in:
- deep water culture (rafts)
- NFT channels
- media bed (ebb and flow)
- wicking bed
- soil bed
Growing media
The substrate the roots sit in. Choice depends on the system (clay pebbles don't fit NFT channels; rockwool isn't used in media beds) and the crop (tatsoi works in the media listed below).
| Medium | pH effect | Water retention | Bacterial surface |
|---|---|---|---|
| Rockwool (Mineral wool) | alkaline until pre-soaked | very high | low |
| Expanded clay pebbles (LECA) | neutral / inert | low | high |
| Coco coir (Coconut coir) | slightly acidic | high | moderate |
| Net pot, no medium (Bare-root) | - | - | - |
| Soil-based mix (Potting soil) | varies by source | high | high |
Bacterial surface area matters for aquaponics: clay pebbles, lava rock, and pumice double as biofilter substrate. Low-surface media (rockwool, perlite, pea gravel) work in hydroponics but need a separate biofilter in aquaponics.
Nutrient demand by stage
NPK ratios are relative weights at each growth stage; the nutrient mix calculator scales them to absolute grams or ml. EC targets shift through the plant's life: seedlings need a much lighter solution than fruiting adults.
| Stage | N | P | K | EC target (mS/cm) |
|---|---|---|---|---|
| seedling | 1 | 1 | 1 | 0.7 |
| vegetative | 3 | 1 | 2 | 1.6 |
Companion-growing notes
- Heavy uptake of calcium. Co-grown crops with the same demand will end up deficient even at "correct" EC. Plan around this in shared reservoirs.
Aquaponics suitability
Compatible with typical aquaponics nutrient profiles. Fish waste provides enough nitrogen for healthy growth; supplemental potassium, calcium, and iron may still be needed depending on fish stocking density.
Care notes
A fast, easy, cold-tolerant hydroponic green. EC 1.2-2.0 mS/cm. pH 5.5-7.0. Temperature: 5–25°C (one of the most cold-tolerant Asian greens; produces through winter). Moderate light (DLI 12-18 mol/m2/day). Any hydroponic system works. From seed to baby leaf: 3-4 weeks. Full rosettes: 5-7 weeks. Harvest whole rosettes or outer leaves for cut-and-come-again production. The flat rosette shape makes efficient use of growing space. The dark, glossy leaves are attractive in salad mixes. Succession plant every 2-3 weeks. Flea beetles are the main pest. Tatsoi's cold tolerance makes it one of the best crops for winter hydroponic production in minimally heated greenhouses. For commercial growers, baby tatsoi in salad mixes adds visual contrast and a mild Asian green flavor that customers enjoy.
Verified against: rhs-uk. Last reviewed 2026-05-15.