Why is lettuce revenue counted in heads rather than kilograms?

Lettuce is sold by the head, so revenue follows the number of saleable heads a greenhouse produces in a year. A greenhouse producing heavy heads slowly can earn less than one producing lighter heads on a shorter turn, which is the opposite of how a fruiting crop is judged.

Why is a lettuce project planned around a named cultivar?

Head mass, density tolerance and tipburn risk are cultivar properties rather than type properties. The type sets head form and leaf shape; the cultivar sets what the greenhouse is dimensioned for, so the choice belongs in the brief before the design.

Crops · Leafy green

Lettuce.

Q: What decides how many cycles a year a lettuce greenhouse delivers?

The system layout more than the climate. The movement of plants through the greenhouse, the spacing changes as heads expand and the harvest and replant turnaround set the cycle count; the climate envelope itself is narrow rather than demanding.

A short cycle repeated all year, where the head is the unit sold.

Grow lettuce under glass The varieties

First, what leaves the greenhouse?

The head.
The roots. The specification.

A buyer’s specification defines the harvest. Head form, root presentation and target weight guide the choice of cultivar, final spacing and harvest stage.

Whole heads

The shape, leaf texture and packed appearance define the product. Baby leaf and cut-leaf production follow a different harvest plan.

Root ball or trimmed

Living lettuce retains its root ball—the kluit. Root-removed heads require a different harvest and packing operation. Both can be whole-head products.

Weight and space

A larger target head generally needs more growing space and/or time. Cultivar and growing conditions determine the actual relationship; weight alone cannot set plant density.

The schedule depends on the growing conditions

Same area.
A different season.

A summer schedule cannot simply be carried into winter. Local daylight, temperature and humidity influence crop development and marketable quality—and the greenhouse systems needed to maintain the plan.

Light & crop timing

Seasonal light changes the growth available each day. A longer growing stage occupies space for longer and reduces the flow of heads through the same area.

Temperature & leaf quality

Temperature, humidity and air movement need to be considered together. The aim is a consistent harvest, with climate management matched to the cultivar and season.

Water & root environment

Water quality, nutrient-solution temperature and oxygen availability matter in hydroponic cultivation. The root environment is part of the growing plan.

Technology serves the cultivation plan

Different systems.
The same starting question.

How does the method deliver the intended head, at the required pace, with a workable harvest and cleaning routine?

Soil beds

A soil-based route with bed preparation, irrigation and crop handling designed around the site. Organic certification depends on the applicable standard and the full growing practice; soil cultivation alone does not establish it.

Moving gutters · MGS

Crop movement and progressive spacing can release room as plants develop and bring work to defined stations. Moving gutters may use NFT: movement and water delivery describe different parts of the same system. The full spacing schedule, including transfer steps, is needed for a capacity calculation.

Fixed NFT channels

A shallow flow of nutrient solution supplies roots in channels. Channel layout, plant spacing, water distribution, cleaning and transplant handling determine how the growing area is used.

Floats on ebb-and-flow tables

Lettuce is held in plant carriers on tables fitted with ebb-and-flow trays. Periodic flooding supplies water to the root zone, followed by drainage. This table-based approach differs from both a thin nutrient flow in NFT channels and continuously floating rafts in a deep-water pond. Direct sowing into the carriers can change the propagation and transfer workflow. Carrier spacing, occupied table area, irrigation cycles, cleaning and harvest handling form part of the cultivation plan.

Floats on an aerated cultivation floor

A related arrangement places supported plant carriers above an ebb-and-flow cultivation floor. The floor alternates water delivery with air supply beneath the crop, connecting root-zone irrigation with air movement around the plants. This is a floor-based arrangement, with its own irrigation, aeration, hygiene and handling requirements. Its crop schedule and usable area need to be established for the intended lettuce product.

Deep-water culture

Plants are supported above nutrient solution, commonly on rafts. Raft handling, oxygenation, spacing changes and cleaning need to be considered alongside the harvest specification.

Days, not weeks

Lettuce is mostly water, and what it carries beyond that is eaten exactly as it left the plant. Vitamin C, potassium and folate sit in the leaf, and a salad is never cooked, so nothing is boiled out and nothing is added back. The leaf is both the crop and the meal.

Water is also why the head is fragile. A cut lettuce goes on living and goes on losing moisture, and it spends its own condition doing it. A fruit can finish ripening on the way; a leaf only gets older. Turgor, colour and shelf life all start running down at the hour of cutting.

That puts distance at the centre of the argument. A greenhouse near its market can cut in the morning and deliver the same day, and the head reaches the plate with most of its life still ahead of it. It can also do that in every month of the year, which is the part an open field in a hard climate cannot promise.

Nutrition facts

Lettuce, green leaf, raw

Per 100 g

Energy: 15 kcal
Fat: 0.15 g
Carbohydrate: 2.87 g
Sugars: 0.78 g
Fiber: 1.3 g
Protein: 1.36 g
Sodium: 28 mg
Potassium: 194 mg
Vitamin C: 9.2 mg

Source: USDA FoodData Central, FDC 169249

Which lettuce?
The commercial classes.

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

Butterhead Lettuce

Butterhead is the soft-leaved wholehead lettuce sold with its outer leaves intact, and the type most European buyers picture when they specify lettuce.

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.

Red Oakleaf Lettuce

Red oakleaf lettuce carries the lobed leaf of the oakleaf types with red pigmentation, and most often reaches the consumer inside a multi-type pack.

Lettuce is sold by the head, not by the kilogram, and that single fact reorganises the economics. Revenue follows the number of saleable heads a greenhouse produces in a year, so the design questions are cycle length, planting density and the share of heads that reach grade. A greenhouse that produces heavy heads slowly can earn less than one producing lighter heads on a shorter turn, which is the opposite of how a fruiting crop is judged.

What the crop needs

The crop is short-cycle and hydroponic, and it is planted and cleared many times a year. That rhythm makes the system layout as important as the climate: the movement of plants through the greenhouse, the spacing changes as heads expand and the harvest and replant turnaround all set how many cycles a year the building can actually deliver. The climate envelope itself is narrow rather than demanding.

What separates the varieties

The commercial types divide by head form and leaf shape — butterhead, Batavia, crispy, oakleaf, incised, Lolla and romaine — and increasingly by cultivar within each type. A lettuce project is planned around a named cultivar because head mass, density tolerance and tipburn risk are cultivar properties rather than type properties. Romaine carries the highest tipburn risk of the family, because its upright head encloses the fastest-growing leaf margins where air moves least.

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

The greenhouse behind lettuce