Garlic

Quick facts

Category

roots bulbs

Difficulty

intermediate

Days to harvest

240 to 300 days

Harvest type

single harvest then replant

Spacing

15 cm between plants

Environment

Temperature

4–25°C

pH

6 to 7

EC (hydroponic)

1.4 to 1.8 mS/cm

Daily light

15 to 25 mol/m²/day

Climate and zones

USDA zones

3 to 9 (winter low around -40°C or warmer)

Frost tolerance

very hardy (survives deep cold)

Season

cool (spring and fall crops)

Viable growing environments:

• outdoor year-round (in zone)
• outdoor in growing season (annual)
• unheated greenhouse / hoop house
• indoor (heated home)

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

Garlic 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 (garlic 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 phosphorus. Co-grown crops with the same demand will end up deficient even at "correct" EC. Plan around this in shared reservoirs.
• Releases compounds through the roots that can mildly inhibit other crops in the same reservoir or bed. The effect is usually subtle but worth knowing if neighbors look stunted.

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 challenging hydroponic crop because bulb formation requires specific day-length and temperature triggers that are difficult to replicate in controlled environments. Garlic cloves are planted in fall, grow through winter, and form bulbs as days lengthen in spring/summer. This natural cycle takes 7-9 months. In hydroponic media beds: plant individual cloves (pointed end up, 5–8 cm deep) in autumn. EC 1.5-2.5 mS/cm. pH 6.0-7.0. Temperature: cold tolerance through winter (garlic needs 4-8 weeks below 5°C for vernalization, which triggers bulb formation in spring). Full sun during the growing season (DLI 16-22 mol/m2/day). Hardneck varieties are better for cold-climate growers. Harvest in summer when the bottom 3-4 leaves have browned but the top 4-5 are still green. Cure bulbs in a warm, dry, well-ventilated space for 2-4 weeks before trimming and storing. Garlic scapes (the curly flower stalks of hardneck varieties) are a bonus harvest in late spring, with a mild garlic flavor excellent in pesto. For aquaponics growers, garlic in outdoor media beds follows the natural seasonal cycle and integrates well with other root and allium crops.

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