Green Incised Lettuce — DutchGreenhouses

A deeply cut leaf aimed at density and automated harvest

Green incised lettuce has a finely divided leaf margin that gives a distinctive texture in a pack. It is positioned by breeders towards high-density production and mechanised harvesting, which is a different commercial proposition from a wholehead sold by the piece.

What the crop needs

The crop is short-cycle and hydroponic. The claim attached to the type is that it suits close spacing and automatic harvest, and both of those are system decisions that have to be designed for: close spacing changes the climate inside the canopy, and automated harvest sets requirements for uniformity and for the growing system’s geometry.

What the greenhouse has to do

Incised lettuce is aimed at density and at automated harvest, and automation is a building decision before it is a machine purchase. Gutter or bench layout, aisle width, floor tolerance and the route to the pack area all have to suit the harvester, and retrofitting a house that was laid out for hand cutting is expensive.

Density then carries the economics. Plants per square metre set the water system and the light requirement, and a machine cuts a whole batch on one pass, so it is the least even part of the floor that decides the grade. Uniform transmission, uniform air movement and uniform water delivery are the specification the harvest method depends on.

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 incised 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 incised 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