Bok choy
Brassica rapa subsp. chinensis
Also known as: Pak choi, Chinese cabbage, White cabbage, Pak choy, Buk choy, Bai cai, White cabbage (Chinese), Chinese white cabbage
Quick facts
- Category
- leafy greens
- Difficulty
- beginner
- Days to harvest
- 35 to 50 days
- Harvest type
- single harvest then replant
- Spacing
- 20 cm between plants
Environment
- Temperature
- 10–22°C
- pH
- 6 to 7
- EC (hydroponic)
- 1.5 to 2.5 mS/cm
- Daily light
- 12 to 17 mol/m²/day
Climate and zones
- USDA zones
- 4 to 9 (winter low around -34°C or warmer)
- Frost tolerance
- tolerates light frost
- 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
Bok choy 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 (bok choy 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 | 0.8 |
| vegetative | 3 | 1 | 2 | 1.8 |
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
An excellent and fast-growing hydroponic crop, particularly suited to Asian vegetable production. EC 1.2-2.0 mS/cm. pH 5.5-7.0. Temperature: 15–24°C (cool-season crop; bolts quickly above 26°C). Moderate light (DLI 12-18 mol/m2/day). From seed to baby bok choy harvest: 3-4 weeks. Full-sized harvest: 6-8 weeks. Works perfectly in NFT, DWC, raft, and vertical systems. The compact rosette shape makes efficient use of growing space. Succession plant every 2-3 weeks for continuous harvest. In warm conditions, choose heat-tolerant varieties ('Mei Qing Choi', 'Win-Win') that resist bolting. Nutrient demand is moderate; standard leafy green formulation works. Flea beetles and caterpillars (cabbage loopers, diamondback moth) are the main pests in open greenhouse systems; row cover or BT (Bacillus thuringiensis) spray controls caterpillars. For commercial hydroponic growers, baby bok choy is a high-value crop ($6-12/kg) with fast turnover. In aquaponics, bok choy thrives in the nutrient-rich water and grows noticeably faster than in conventional hydroponics.
Verified against: rhs-uk, university-of-arizona-ccac. Last reviewed 2026-05-15.