Radish
Raphanus sativus
Also known as: Spring radish, European radish, Garden radish, Rabano
Quick facts
- Category
- roots bulbs
- Difficulty
- beginner
- Days to harvest
- 25 to 35 days
- Harvest type
- single harvest then replant
- Spacing
- 5 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
- 2 to 10 (winter low around -46°C or warmer)
- Frost tolerance
- frost hardy (handles regular 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
Radish works in:
- 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 (radish works in the media listed below).
| Medium | pH effect | Water retention | Bacterial surface |
|---|---|---|---|
| Soil-based mix (Potting soil) | varies by source | high | high |
| Coco coir (Coconut coir) | slightly acidic | high | moderate |
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 | 2 | 1 | 2 | 1.8 |
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
The fastest root crop for hydroponic systems. Media beds or containers with 8–12 cm of loose substrate for standard salad radishes (deeper for daikon types). EC 1.2-2.0 mS/cm. pH 6.0-7.0. Temperature: 10–22°C (cool-season; above 25°C, roots become pithy, hollow, and excessively peppery). Moderate light (DLI 12-18 mol/m2/day). From seed to harvest: 22-30 days for standard salad radishes, making them the fastest root crop available. Direct seed (radishes don't transplant well). Thin to 3–5 cm spacing. Harvest when the root top is 2–3 cm diameter at the soil line; delay causes cracking, pithiness, and increasing heat. Succession plant every 2 weeks for continuous supply. The greens are edible and peppery; use in salads, pesto, or sauteed like turnip greens. Watermelon radish ('Red Meat') takes longer (50-60 days) but produces a stunning, Instagram-worthy cross-section. For aquaponics media beds, radishes are the ideal quick-gratification crop between longer-season plantings.
Verified against: rhs-uk, university-of-arizona-ccac. Last reviewed 2026-05-15.