Seed Trays vs Module Trays: Which to Use

Short answer: for most beginners, module trays win. Each seedling grows in its own cell, so you lift it out as a neat plug with the roots barely disturbed. Open seed trays still earn their place for crops you sow thickly and prick out — but they take a bit more skill. Here's how to choose.

Open seed trays vs module/plug trays

The two are simply shaped differently, and that shape decides how you handle the seedlings.

Open seed trays are one shallow, undivided container. You scatter or sow seed across the surface, the seedlings come up in a mat, and you later lift each one out (pricking out) into a pot or module to grow on. They're cheap, hold a lot of seed, and let you pick only the strongest seedlings — but every plant gets its roots teased apart at least once.

Module trays (also called plug trays or cell trays) are divided into separate cells — often 6, 12, 24 or 40. You sow one or two seeds per cell, and each seedling grows in its own little block of compost. At planting time you push the whole plug out, roots intact, and pop it straight into the ground or a pot. Less faff, less check to growth, fewer losses.

When each is best

Neither is "right" — they suit different jobs.

Choose module trays when:

• You're new and want the simplest path from sowing to planting out.
• The crop resents root disturbance (see the next section).
• You want sturdy, evenly spaced plants with a predictable planting date.
• You're sowing in succession — a few cells at a time, every couple of weeks.

Choose open seed trays when:

• You're sowing a lot of one thing cheaply (a tray of mixed salad leaves, say — see growing lettuce).
• The crop transplants happily, like brassicas you'll prick out into bigger modules.
• You're confident pricking out tiny seedlings by a seed leaf, never the stem.

For nearly everything else, modules save time and seedlings. They're the kit we'd point a first-year grower to in the starter buying guide, and they pair naturally with the steps in how to start a vegetable garden.

Crops that need modules (root-disturbance haters)

Some seedlings sulk — or bolt, or simply die back — if their roots are torn during pricking out. Sow these one per cell in modules and never disturb them until you plant out the whole plug:

• Beans — runner and French. See growing beans.
• Peas — sow a few per deep module or a length of guttering.
• Courgettes, pumpkins and squash — big seeds, fast roots, easily set back. See growing courgettes.
• Cucumbers — sow singly and keep warm. See growing cucumbers.
• Sweetcorn — resents root disturbance badly; modules or deep cells only.
• Brassicas (cabbage, broccoli, kale) — happiest moved as plugs.
• Beetroot — sow a cluster per cell and plant the whole lot out. See growing beetroot.

Root crops like carrots and parsnips are the exception either way — they're best sown direct where they'll grow, because any transplanting tends to fork the root. Skip trays for those entirely.

Reusable vs biodegradable, and DIY

You'll see three broad types on the shelf:

Rigid plastic trays are the workhorse. The cheap thin ones crack after a season; sturdier moulded trays last for years if you store them out of frost and sun. Best value over time, and easy to wash and reuse.

Biodegradable pots and modules — coir, paper or fibre — let you plant the whole thing without disturbing roots, which is genuinely handy for the root-haters above. The trade-offs: they dry out fast, can wick moisture away from the compost, and some fibre pots are slow to break down and can check roots if they sit dry. Soak them well before planting and tear the rim off below soil level.

DIY and reused is free and works fine. Toilet-roll tubes make perfect deep modules for peas and beans; clear takeaway tubs become mini propagators; yoghurt pots with a drainage hole sown singly act as modules. Our guide to reusing and recycling in the garden has more ideas — for many beginners this is the cheapest, greenest start of all.

Whatever you pick, the bigger wins are warmth, light and not overwatering. Get those right and both trays will grow you strong seedlings. For the full kit list to get going, head back to the starter buying guide.