Carrot

Quick facts

Category

roots bulbs

Difficulty

intermediate

Days to harvest

60 to 80 days

Harvest type

single harvest then replant

Spacing

5 cm between plants

Environment

Temperature

7–24°C

pH

6 to 6.8

EC (hydroponic)

1.6 to 2 mS/cm

Daily light

14 to 22 mol/m²/day

Climate and zones

USDA zones

3 to 10 (winter low around -40°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

Carrot 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 (carrot 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.

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 moderately challenging hydroponic root crop requiring deep, loose growing medium. The taproot needs 15–25 cm of unobstructed, fine-grained substrate (perlite, vermiculite, or washed sand) to develop straight. Any stones, compacted areas, or obstructions cause forking. Standard water-culture systems (NFT, DWC) cannot grow carrots; media beds or deep containers are necessary. EC 1.5-2.5 mS/cm. pH 6.0-6.8. Temperature: 15–24°C (cool-season crop; above 28°C, roots become pale, fibrous, and bitter). Moderate light (DLI 12-18 mol/m2/day). From seed to harvest: 65-80 days for standard varieties, 50-60 days for baby types ('Adelaide', 'Atlas'). Sow seeds directly into the growing medium (carrots don't transplant well because the taproot is disturbed). Thin seedlings to 3–5 cm spacing. Harvest when the root tops are 1.5–2 cm diameter at the soil line. Short and round varieties ('Paris Market', 'Thumbelina') are better suited to shallow media beds than long varieties ('Imperator'). The greens (carrot tops) are edible and flavorful: use in pesto, chimichurri, or as a herb garnish. For aquaponics media beds, carrots grow well alongside other root crops in the same bed.

Notable varieties

A starting shortlist of cultivars worth knowing about. Not exhaustive: the seed catalogs list hundreds of named varieties. These are the ones home growers commonly choose between.

Further reading

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