Genovese basil / Sweet basil (Ocimum basilicum) growing guide

Quick facts

Category: herbs soft
Difficulty: beginner
Days to harvest: 40 to 60 days
Harvest type: cut leaves, plant regrows for repeated harvests
Spacing: 25 cm between plants

Environment

Temperature: 18–28°C
pH: 5.5 to 6.5
EC (hydroponic): 1 to 1.6 mS/cm
Daily light: 18 to 25 mol/m²/day

Climate and zones

USDA zones: 10 to 13 (winter low around -1°C or warmer)
Frost tolerance: frost sensitive (dies at first frost)
Season: warm (summer crops, frost-sensitive)

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

Genovese basil works in:

deep water culture (rafts)
NFT channels
vertical / aeroponic tower
media bed (ebb and flow)
wicking bed
drip / Dutch buckets
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 (genovese basil 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	0.8
vegetative	2	1	2	1.4

Companion-growing notes

High transpiration. Reservoir level will need regular top-ups during fruiting or flowering.

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 single most popular hydroponic herb crop worldwide. EC 1.0-1.8 mS/cm. pH 5.5-6.5. Temperature: 20–28°C (critical: below 15°C causes chilling injury, blackened leaves, and growth arrest). High light (DLI 15-25 mol/m2/day; basil is one of the most light-demanding herbs). Grows well in NFT, DWC, Kratky, drip, and vertical systems. From seed to first harvest: 4-5 weeks. Pinch the growing tip above the second set of true leaves to promote branching; each pinch doubles the number of growing tips, creating a bushier plant with more harvestable leaf area. Continue pinching every 2-3 weeks. Remove flower buds immediately: once basil flowers, leaf production slows and flavor changes (becomes more bitter). Nitrogen is the key nutrient for leaf production; maintain adequate N throughout the crop. Fusarium wilt (Fusarium oxysporum f. sp. basilicum) is the most serious disease in hydroponic basil; use resistant varieties ('Nufar', 'Prospera') in commercial operations. Downy mildew (Peronospora belbahrii) is an increasingly common problem; good airflow and resistant varieties help. For home growers, Genovese basil in a DWC or Kratky setup is the classic first hydroponic crop.

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.

Cultivar	Type	Days	Notes
Genovese	open-pollinated	60	The DOP-protected Italian variety from Liguria, the traditional pesto basil. Large smooth oval leaves, intense sweet anise-clove flavor. Slow to bolt compared to most basils.
Aroma 2	open-pollinated	65	Improved Genovese with stronger fusarium resistance. Slightly smaller leaves, same flavor profile. The commercial greenhouse standard in much of Europe.
Lettuce-leaf	open-pollinated	65	Crinkled leaves up to 10cm across (lettuce-sized rather than basil-sized). Milder than Genovese, less intense pesto but useful for wrapping and layering whole leaves in sandwiches.
Spicy Globe	open-pollinated	60	Compact tight-mounding form, tiny pointed leaves on a 25-30cm sphere. Ornamental in containers, flavor slightly more peppery than Genovese. Naturally late to bolt.