Water spinach

Quick facts

Category

leafy greens

Difficulty

beginner

Days to harvest

35 to 50 days

Harvest type

cut leaves, plant regrows for repeated harvests

Spacing

15 cm between plants

Environment

Temperature

20–32°C

pH

5.5 to 7

EC (hydroponic)

1 to 2 mS/cm

Daily light

14 to 22 mol/m²/day

Climate and zones

USDA zones

9 to 13 (winter low around -7°C or warmer)

Frost tolerance

frost sensitive (dies at first frost)

Season

year-round tropical (needs consistent warmth)

Viable growing environments:

• outdoor in growing season (annual)
• 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

Water spinach 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 (water spinach works in the media listed below).

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.

Companion-growing notes

• Heavy uptake of nitrogen. Co-grown crops with the same demand will end up deficient even at "correct" EC. Plan around this in shared reservoirs.
• High transpiration. Reservoir level will need regular top-ups during fruiting or flowering.

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 supremely productive warm-weather hydroponic/aquaponic green, but with legal restrictions in the US. Check federal and state regulations before growing. EC 1.5-2.5 mS/cm. pH 5.5-7.0. Temperature: 25–35°C (tropical; frost kills the plant). High light (DLI 16-25 mol/m2/day). The semi-aquatic nature makes it ideal for NFT, DWC, and raft systems where roots are in constant water contact. Also grows directly in fish tank water or in flooded media beds. From cutting to first harvest: 3-4 weeks. Growth is extremely vigorous in warm, nutrient-rich water. Harvest by cutting the top 20–30 cm of growing tips; the plant resprouts rapidly from every cut node. Continuous harvesting every 1-2 weeks keeps the plant productive. For the classic stir-fry: cut stems into 5 cm pieces, stir-fry over very high heat with garlic, chile, and fermented bean paste or shrimp paste for 60-90 seconds. The stems should still be slightly crunchy. The productivity in warm aquaponics systems is unmatched by any other leafy green.

Legality

Some edible crops are regulated as noxious weeds or invasive species in regions outside their native range. This table reflects the rules as of the verified date on each row; verify with your local agriculture or environmental authority before planting, especially for outdoor systems.

Further reading

• Best crops for hydroponic beginners
• The Kratky method: grow lettuce with zero electricity