Lettuce

Butterhead Lettuce.

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

Soft leaves, short journeys

Butterhead is mostly water, and the small remainder is the reason it is on the plate: vitamin C, potassium and folate, eaten raw and none of it cooked away. A soft leaf is a leaf full of water, which is the same thing that makes the type pleasant to eat and difficult to move.

Softness sets the clock. The head bruises where it is handled and wilts where it waits, so every extra transfer, crate and cold-store day shows on the outer leaves a buyer looks at first. What is lost is condition rather than content, but condition is what a wholehead is graded on.

Distance decides how much of that is spent before the head arrives. A greenhouse near its market moves the crop from cutting to shelf in one short chain, with fewer transfers and less time in the box. Trimmed outer leaves are the waste line on a soft type, and a short chain is what keeps them on the head.

Nutrition facts

Lettuce, butterhead, raw

Per 100 g

Energy: 13 kcal
Fat: 0.22 g
Carbohydrate: 2.23 g
Sugars: 0.94 g
Fiber: 1.1 g
Protein: 1.35 g
Sodium: 5 mg
Potassium: 238 mg
Vitamin C: 3.7 mg

Source: USDA FoodData Central, FDC 168429

Butterhead is the soft-leaved wholehead lettuce sold with its outer leaves intact, and it is the type most European buyers picture when they specify lettuce. The leaf is tender and bruises easily, so handling from harvest to pack decides as much of the grade as growing does.

What the crop needs

The crop is short-cycle and hydroponic, planted and cleared many times a year. The head has to close evenly without becoming so dense that the inner leaves cannot transpire, which is the condition tipburn develops in. Spacing, cycle length and the climate at the end of the cycle are the levers, and the system layout decides how many cycles the building actually delivers.

What the greenhouse has to do

Butterhead is soft, and softness is fragile. The head bruises in handling and loses condition quickly once cut, so the distance from the furthest row to the cold chain is a layout decision rather than a logistics problem to be solved after the house is built.

The rest follows the cycle. A short-cycle crop turns many times a year, so the house is a throughput machine: planting density, the recirculating water system and the harvest route decide annual output more than any single setpoint does. Air movement earns its own line, because tipburn follows transpiration at the leaf margin and even air through the canopy is the control for 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.

Crop data Butterhead lettuce

Day climate

Air temperature: 21–22.7 °C¹
Relative humidity: 60–80 %¹
Daily light integral: 11.5–13.2 mol/m²/d¹
Photoperiod: 14–17 hDutchGreenhouses practice
CO₂ concentration: 1000–1100 ppm¹

Irrigation and root zone¹

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

Sources (1)

WUR, 2018, WPR-813 — Lettuce on water under glass with LED E067

Sourced rows carry their references; system rows are DutchGreenhouses practice. Neither is a specification — setpoints are calculated per greenhouse, crop and location.

Questions

Butterhead 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.

Other lettuce
varieties.

Repeat harvests. Consistent head quality and size. The class you sell decides the plant load, the harvest rhythm and the house.

Green Crispy Lettuce

Green crispy is the dense, crunchy-leaved lettuce sold both as a wholehead and into processing, where the leaf holds its texture after cutting.

Green Oakleaf Lettuce

Green oakleaf lettuce is a lobed, soft-leaved head grown for leaf shape rather than for weight.

Lollo Bionda Lettuce

Lollo Bionda is the green Lolla lettuce, with a tightly curled leaf margin and bought for appearance rather than for weight.

Lollo Rosso Lettuce

Lollo Rosso is the red Lolla lettuce, where the tightly curled leaf margin and the red pigmentation are both the product.

Red Crispy Lettuce

Red crispy is the red-pigmented counterpart of the green crispy head, sold wholehead and into mixed-leaf packs where colour intensity is part of the specification.