Why Won't My Seeds Germinate?

Empty seed trays are disheartening, but it is almost always one of a handful of fixable things. Most germination failures come down to temperature, moisture, sowing depth or simply old seed — sort those and the seedlings follow.

Ranked causes and fixes

Work down this list in order — the first two cause the most empty trays.

1. It's too cold. This is the number one reason seeds sit and do nothing. Most veg need warmth to trigger germination: tomatoes and peppers want 18–21°C, and even hardy crops sulk below about 7°C. A cold windowsill, an unheated greenhouse in March, or chilly outdoor soil will all stall things. The fix: bring seed trays indoors to a warm spot, use a heated propagator for heat-lovers, and outdoors simply wait. In a cold spring, hold off direct-sowing until the soil warms — late April or May for most things.

2. Too wet or too dry. Seeds need steady, even moisture — not a bog, not a desert. Waterlogged compost starves seeds of air and rots them; this also invites damping off, which kills seedlings just as they emerge. Compost that dries out, even once, can kill a germinating seed in hours. The fix: keep compost damp like a wrung-out sponge. Water trays from below where you can, and cover with a clear lid or a freezer bag to hold moisture until they're up.

3. Sown too deep. A buried seed exhausts its energy before it reaches the light. As a rule, sow at roughly twice the seed's own depth — fine seed like lettuce barely needs covering, while a bean goes 3–5cm down. The fix: check the packet, and when in doubt sow shallower rather than deeper.

4. Old or poorly stored seed. Viability drops with age, and heat or damp speeds the decline. Parsnips are notorious — buy fresh each year. The fix: use seed within its packet date, store spares somewhere cool, dark and dry, and if you're unsure, do a quick test (see below).

5. It's a naturally slow crop. Sometimes nothing is wrong — you're just impatient. Radishes and beans are up in days, but carrots, parsley and parsnips routinely take two to three weeks. The fix: label your sowings with the date, check the packet's expected timing, and give slow ones their full window before giving up.

How to get reliable germination

Get these four right and most seeds come up without fuss.

• Warmth. Start tender crops indoors on a warm windowsill or in a propagator. Use the planting calendar to sow at the right time, and don't rush outdoor sowing in a cold spring.
• Even moisture. Pre-moisten your compost before sowing, cover trays to lock in humidity, and never let them dry out. Lift the cover once seedlings appear so they don't sit damp.
• Correct depth. Twice the seed's depth, no more. Firm the compost gently so seeds make good contact, and barely cover the fine stuff.
• Fresh seed and good compost. Buy seed for the current season and sow into fresh, fine seed or peat-free multipurpose compost — lumpy or tired compost gives patchy results.

If you sowed into open ground and suspect slugs rather than germination, check the slugs and snails guide — they can clear a row of seedlings overnight, leaving bare soil that looks like nothing came up. And if seedlings do appear but grow pale and floppy, that's a light problem covered in leggy seedlings.

Once you've got reliable germination cracked, the rest of the season gets a lot easier — head back to the start a vegetable garden guide for what comes next, from potting on to planting out.

PS: when in doubt, sow a few extra. Seeds are cheap, and a spare row is the simplest insurance against a patchy result.