Green Crispy Lettuce — DutchGreenhouses

A dense, crunchy head that suits both wholehead sale and high density

Green crispy is the dense, crunchy-leaved type sold both as a wholehead and into processing, where the leaf holds its texture after cutting. The portfolio of cultivars is unusually wide for a single lettuce type, because breeders have selected separately for wholehead sale and for high-density production.

What the crop needs

The crop is short-cycle and hydroponic. A dense head is the product and also the risk: the tighter the head closes, the harder it is for the inner leaf to transpire, and the more the climate at the end of the cycle decides whether the crop finishes clean. Spacing is a cultivar-by-product decision rather than a fixed rule.

What the greenhouse has to do

Green crispy is grown two ways — as a wholehead sold by the piece, and at high density for processing — and the house is dimensioned differently for each. Density sets plants per square metre, and that in turn sets the water system, the light requirement and the harvest method together. The decision belongs before the building, not after it.

A dense head also wants light. Heads that fill unevenly across the floor arrive at the same harvest day at different weights, and a batch harvested as one unit is graded on its worst heads. Even transmission and even air movement are what keep a batch together, which is why the screening strategy and the ventilation are specified with the density rather than around it.

DutchGreenhouses® designs the structure, climate, screening and irrigation around the lettuce type, its system and the local climate, so cycles turn at the head quality the market grades on. Get in touch to plan a lettuce greenhouse.

Butterhead lettuce

Soft, loosely wrapped leaves, and the type least tolerant of handling.

Greenleaf / Batavia lettuce

A firmer, more robust head than butterhead, and it travels better.

Romaine lettuce

The upright head, and the tipburn risk that comes with it.

Hydroponics

Substrate growing with drip supply and drain recirculation.

Climate

Heating, cooling, humidity control and carbon dioxide dosing.

Questions

Green crispy lettuce, asked and answered

Is head weight or head count the right target?

Lettuce is sold by the head, so the count reaching grade in a year decides revenue. A heavier head grown more slowly can earn less than a lighter head on a shorter cycle.

Does the cultivar matter more than the type?

For head mass, density tolerance and tipburn risk, yes. Those are cultivar properties, which is why a lettuce project is planned around a named cultivar rather than around the type alone.

What causes tipburn?

Calcium not reaching the fastest-growing leaf margins, driven by transpiration and root pressure rather than by supply. Climate control addresses it; adding calcium to the solution generally does not.

Crop data

Green crispy lettuce — reference values

Reference values from the DutchGreenhouses crop model, each traced to its Dutch source below. Ranges describe published practice across systems and seasons; a project setpoint is calculated for the actual greenhouse, crop and climate.

Day climateMedium confidence¹

Air temperature: 21–22.7 °C
Relative humidity: 60–80 %
Daily light integral: 11.5–13.2 mol/m²/d
CO₂ concentration: 1000–1100 ppm

Irrigation and root zoneMedium confidence¹

Supply EC: 1.6–1.8 mS/cm
Supply pH: 5.5–6 pH

Where these come from

WUR, 2018, WPR-813 — Lettuce on water under glass with LED. WUR research report · High confidence · E067Primary direct evidence, but one research greenhouse and four named lettuce types/cultivars. Numeric values are operating observations, not universal optima.

These are reference values, not a specification. DutchGreenhouses does not publish project setpoints; those are calculated per greenhouse, crop and location.

From the knowledge base