Red Crispy Lettuce — DutchGreenhouses

The crispy head in red, where colour development is part of the grade

Red crispy is the red-pigmented counterpart of the green crispy head, sold wholehead and into mixed-leaf packs where its colour is the reason it is there. Colour intensity is part of the specification, not a bonus, and it develops in response to light rather than to nutrition.

What the crop needs

The crop is short-cycle and hydroponic. It carries the same density and tipburn considerations as green crispy, with the added requirement that the head colours evenly. Light reaching the outer leaf is what drives pigment, so spacing and any shading strategy affect the grade directly rather than only the growth rate.

What the greenhouse has to do

Colour is part of the grade here, and colour is a light response. A red crispy head that finishes pale is downgraded whatever it weighs, so the light plan is specified for pigment development as well as for growth, and the screening strategy has to give the crop the light it needs without the heat load that comes with it.

The rest is dense-head lettuce. The crop turns quickly, so density, the recirculating water system and the harvest route decide annual output. Because a batch is cut as one unit, unevenness across the floor shows up as split colour within a single harvest — which makes even transmission worth more here than in a green type.

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

Red 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

Red 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