Cauliflower / Cauli (Brassica oleracea var. botrytis) growing guide

Quick facts

Category: leafy greens
Difficulty: advanced
Days to harvest: 80 to 110 days
Harvest type: single harvest then replant
Spacing: 50 cm between plants

Environment

Temperature: 13–22°C
pH: 6 to 7
EC (hydroponic): 1.8 to 2.5 mS/cm
Daily light: 17 to 22 mol/m²/day

Climate and zones

USDA zones: 3 to 10 (winter low around -40°C or warmer)
Frost tolerance: tolerates light 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

Cauliflower works in:

drip / Dutch buckets
media bed (ebb and flow)
soil bed

Root mass is 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 (cauliflower works in the media listed below).

Medium	pH effect	Water retention	Bacterial surface
Rockwool (Mineral wool)	alkaline until pre-soaked	very high	low
Expanded clay pebbles (LECA)	neutral / inert	low	high
Coco coir (Coconut coir)	slightly acidic	high	moderate
Net pot, no medium (Bare-root)	-	-	-
Soil-based mix (Potting soil)	varies by source	high	high

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	1
vegetative	3	1	2	2.2

Companion-growing notes

Heavy uptake of nitrogen, calcium. 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

Not recommended for pure aquaponics. Fish waste alone doesn't provide enough of the nutrients this crop demands (typically potassium, calcium, or boron). It can be grown in a hybrid system where the reservoir is supplemented with hydroponic-style nutrients, but expect to dose actively.

Care notes

One of the most challenging brassica crops for hydroponics due to strict temperature requirements and sensitivity to stress. Large containers or media beds (20 cm depth). EC 2.0-3.0 mS/cm. pH 6.0-7.0. Temperature: 15–20°C during curd formation (critical; temperatures above 25°C or below 5°C cause 'buttoning' (premature, undersized curds), riciness (loose, grainy texture), and browning). The narrow temperature window is the primary difficulty. Moderate to high light (DLI 15-22 mol/m2/day). From transplant to harvest: 65-85 days depending on variety. Harvest when the curd is 15–20 cm diameter, compact, and white (or the target color for colored varieties). If yellow or purple spots appear on white curds, light exposure is the cause; check that the blanching is effective. Calcium and boron supplementation prevents hollow stem and browning of the curd. Caterpillars and aphids are common pests. For hydroponic growers, the temperature sensitivity makes cauliflower a fall/winter crop in most setups. Mini cauliflower varieties ('Snowball Y Improved', 'Snow Crown') produce smaller heads faster and are more forgiving.