Batavian lettuce / Summer crisp lettuce (Lactuca sativa var. capitata (Batavian group)) growing guide

Quick facts

Category: leafy greens
Difficulty: beginner
Days to harvest: 50 to 65 days
Harvest type: single harvest then replant
Spacing: 25 cm between plants

Environment

Temperature: 13–26°C
pH: 5.5 to 6.5
EC (hydroponic): 0.8 to 1.4 mS/cm
Daily light: 12 to 17 mol/m²/day

Climate and zones

USDA zones: 4 to 10 (winter low around -34°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

Batavian lettuce works in:

deep water culture (rafts)
NFT channels
vertical / aeroponic tower
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 (batavian lettuce 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	0.6
vegetative	3	1	2	1.2

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

An excellent hydroponic lettuce type that combines the texture of crisphead with the ease and speed of loose-leaf varieties. EC 0.8-1.5 mS/cm (lettuce is a light feeder). pH 5.5-6.5. Temperature: 15–22°C ideal (tolerates 24–26°C better than crisphead or butterhead types before bolting). Moderate light (DLI 12-17 mol/m2/day). Harvestable in 5-7 weeks from transplant (or 3-4 weeks as baby leaf). Works in NFT, DWC, raft, and vertical tower systems. The thicker leaves have a satisfying crunch that lettuce-leaf varieties lack, making Batavian types popular with consumers who want texture in their salad. Outer leaves can be harvested progressively (cut-and-come-again) while the center continues producing, extending each plant's productive window. Tipburn (calcium deficiency at leaf margins) is less common than in butterhead types because the open head structure allows better airflow to inner leaves. Red-tinged varieties ('Lollo Rossa', 'Magenta') add color to salad mixes and command premium prices. Succession plant every 2-3 weeks for continuous harvest. A top-tier hydroponic lettuce for both home and commercial growers.

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
Nevada	open-pollinated	55	The benchmark heat-tolerant Batavian. Green ruffled heads with thick crisp ribs, holds without bolting through summer in zones 6 and below. The variety US market growers reach for when butterhead season ends in June.
Sierra	open-pollinated	55	Sister variety to Nevada with red-tinged leaf margins. Same heat tolerance, slightly milder flavor. Striking in mixed-color salad pickings.
Cardinale	open-pollinated	55	Deep red-bronze Batavian, classic French market type. Color intensifies in cool weather and softens in heat. Slightly less bolt-resistant than Nevada but a better-looking head.
Concept	hybrid	50	Modern F1 with stronger tipburn resistance than the open-pollinated Batavias. Light green tightly-folded heads, more uniform across a planting block. Common in commercial CSA mixes.
Magenta	hybrid	55	Red Batavian F1 with rosette form and a denser interior than Cardinale. Holds color better in heat and is more bolt-resistant. Useful where you want a red lettuce that won't quit in July.