A 32-cell tray is the density a propagator picks when the seedling is expected to stay in the tray long enough to build a real root ball. The cells on this tray measure 53 x 53 mm at the rim and 27 x 27 mm at the base, 65 mm deep, holding roughly 1000 cc of growing medium each. That is four to five times the volume of a 200-cell plug. The result is a seedling that leaves the tray with an intact root system instead of a bare taproot, and a transplant that does not stall for a fortnight after it is set out.

The tray body is 540 x 280 mm, so it sits two across a standard 1.1 m bench and fits the same carrier rails as the rest of our planting tools range.

The 53 mm rim gives enough surface area to thin by hand without disturbing the neighbouring cell. A workable rate for this cell size is one to two seeds per cell for large-seeded crops such as cucumber, melon and squash, and a pinch of eight to ten for brassicas and tomatoes that are later singled. Depth follows the usual rule of two to three times the seed diameter, which puts most vegetable seed 8 to 12 mm below the surface in a cell this deep.

Because each cell holds its own volume of medium, water does not run from cell to cell the way it does on an open bench. Capillary matting or an ebb-and-flow bench under the tray gives even moisture without wetting the foliage, and the 65 mm depth means the medium column stays damp at the base even if the surface dries between irrigations.

Direct sowing wins on labour and on crops that resent root disturbance. A multi-cell tray wins when the growing season is short, when the soil is still cold, or when the seed is expensive enough that a failed germination in the field is a real loss. At 32 cells the tray sits in the middle: fine enough to raise a transplant that establishes quickly, coarse enough that filling, sowing and lifting stay quick jobs with a bench dibber rather than a plug popper.

Transplant survival rests on how much medium travels with the root. A 32-cell seedling carries roughly a litre of it, which is why growers use this size for courgette, pumpkin and early tomato, and for tree and shrub liners that are moved on once rather than twice.

This tray is one model in a range that runs from 32 to 288 cells, all on the same 540 x 280 mm footprint, so a bench layout does not change when the crop changes. Cell count, wall thickness and carton quantity for every model are given in the table below. Wall thickness is the variable that decides how many seasons a tray gives under UV and handling; the figures listed are measured per model and carton packing is quoted per thickness.

Standards for propagation trays and the growing media they are filled with are set out by FAO in its horticultural guidance, and commercial practice is reported each month by Greenhouse Grower.

Q: Why 32 cells rather than a finer plug tray?
A: Because the seedling is meant to grow on in the tray. A 1000 cc cell lets a root ball form, so the plant lifts cleanly and does not check after transplanting. Finer trays are for short holding periods before pricking out.

Q: How many seeds go into each cell?
A: One to two for large seed such as cucumber and squash, a pinch of eight to ten for brassicas and tomato that will be singled later. Sow two to three times the seed diameter deep, which is 8 to 12 mm for most vegetable seed.

Q: Will the cells dry out at different rates across the tray?
A: Not if the tray stands on capillary matting or an ebb-and-flow bench. Each cell holds its own medium, so water moves up from below rather than across the surface, and the 65 mm depth keeps the base damp between irrigations.

Q: Can the same tray be used for more than one season?
A: Yes, with care. Service life depends on the wall thickness you order, from 0.5 mm up to 1.1 mm, and on how the trays are stacked and washed between crops. Thicker walls resist the flexing that cracks thinner trays.

Q: Does it fit standard bench rails?
A: The tray is 540 x 280 mm, so two sit side by side on a 1.1 m bench. The range is built on that same footprint from 32 up to 288 cells, so rails and irrigation do not change when the crop does.