Water caltrop

Environment

The bounded range this crop tolerates. Strict on light; outside the DLI band, yields drop sharply.

Climate and zones

USDA zones

5–11 (winter low around -29°C)

Frost

frost hardy

Season

warm (summer, frost-sensitive)

Growing systems

Root mass: moderate.

Growing media

Nutrient demand by stage

NPK ratios are relative weights. EC targets shift through the plant's life.

Aquaponics suitability

Care notes

A unique aquatic crop grown in still or slow-moving water, potentially integrable with aquaponics. The plant grows in water 30–150 cm deep, with leaves floating on the surface and roots anchored in bottom substrate or hanging freely. Temperature: 18–30°C (warm-season). Full sun (DLI 18-25 mol/m2/day). Propagate by planting the horned seed cases in containers of muddy substrate submerged in the growing water; the plant spreads by runners across the surface. Harvest the nut-bearing fruits in autumn when the horned cases are firm and dark, and boil the nuts for 30-45 minutes to cook the starchy interior, since raw water caltrop can carry the intestinal fluke Fasciolopsis buski in areas where the parasite is endemic, so always cook thoroughly. For aquaponics it could be grown in fish tanks or connected ponds, but Trapa natans is highly invasive and should never be grown where it could escape into natural waterways; check local regulations, as it is prohibited in many jurisdictions.

Legality

Further reading

• Getting started with hydroponics: which system to build first
• Understanding nutrient solutions: N-P-K, micronutrients, and why your lettuce turned yellow