Lotus

Quick facts

Category

roots bulbs

Difficulty

intermediate

Days to harvest

180 to 365 days

Harvest type

continuous production over weeks or months

Spacing

120 cm between plants

Environment

Temperature

18–32°C

pH

6 to 7.5

EC (hydroponic)

1.2 to 2.5 mS/cm

Daily light

20 to 30 mol/m²/day (strict, will fail outside this range)

Climate and zones

USDA zones

5 to 11 (winter low around -29°C or warmer)

Frost tolerance

very hardy (survives deep cold)

Season

warm (summer crops, frost-sensitive)

Viable growing environments:

• outdoor year-round (in zone)
• outdoor in growing season (annual)
• heated greenhouse

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

Lotus works in:

• media bed (ebb and flow)
• soil bed

Root mass is very heavy - thin-channel systems (NFT, vertical towers) can't hold this crop mechanically, hence the system list above.

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 (lotus 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 potassium. 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 unique aquaponics crop grown directly in the fish system water or in large containers connected to the system. Requires a large, shallow container (60 L, 30 cm wide, 20–30 cm deep) filled with heavy, clay-based aquatic planting media to anchor the rhizome. The container is submerged or partially submerged with 10–20 cm of water above the media surface. Temperature: 22–32°C (tropical; the rhizome survives winter dormancy in zones 5+ if the water doesn't freeze solid, but active growth requires warmth). Full sun (DLI 18-30 mol/m2/day; lotus needs very strong light for flowering and rhizome development). Plant tubers horizontally in early spring, barely covered by media. Growth emerges as floating pads, then aerial leaves, then flowers. Harvest rhizome sections in autumn after the leaves die back, or in early spring before growth resumes. Each plant produces 1–3 kg of rhizome annually once established. For aquaponics, lotus is one of the few crops that can grow directly in the fish tank water, making it a natural integration with tilapia or koi systems.

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