12 Tips for Beginning Seed Gardeners

Raising plants from seed is cheaper than buying seedlings, gives you varieties no nursery stocks, and is not difficult once you know which few things actually matter. Most first-year failures come down to the same handful of causes: sowing at the wrong time for your climate, sowing too deep, letting the mix dry out, or not giving seedlings enough light. Get those right and the rest is detail.

1. Start with what you will actually eat

It is tempting to sow one of everything. Resist it. Pick four or five things your household eats regularly and that suit your climate and the season you are in, and grow those well. A small bed producing lettuce, silverbeet, spring onions and herbs you use every week beats a big bed of things nobody finishes.

2. Read the packet before you open it

The back of a seed packet answers most beginner questions: sowing depth, spacing, whether to sow direct or raise in punnets, days to germination, and the season it suits. It is the single most useful thing to read and the most commonly skipped.

3. Sow for the season, not for the day the seed arrives

Seed keeps. A packet that lands in June is not an instruction to sow in June. Work back from your last frost for warm-season crops, and from the first real heat for cool-season crops. Australia spans six rough climate zones and they do not share a calendar: cool and alpine (Tasmania, Ballarat, the southern tablelands), temperate (Sydney, Melbourne), Mediterranean (Perth, Adelaide), subtropical (Brisbane), tropical (Darwin, Cairns) and arid (Alice Springs, Mildura). What suits Hobart in September suits Darwin at a completely different time of year, if at all.

4. Use a seed raising mix, not garden soil

Garden soil compacts in a punnet, drains badly and brings weed seed and disease with it. A proper seed raising mix is fine, light and low in nutrients, which is what a germinating seed wants. Seeds carry their own food supply, so a rich mix is unnecessary and can burn fine roots.

One safety note that is worth taking seriously: dampen bagged mix before you handle it so it does not raise dust, wear a mask and gloves, and wash your hands afterwards. Potting and seed raising mixes can carry Legionella longbeachae, which causes Legionnaires' disease when the dust is breathed in.

5. Sowing depth is the one that catches everyone

The rough rule is to sow at about twice the seed's own width. That means a broad bean goes in a few centimetres down, and a lettuce or celery seed barely gets covered at all. Some seed, including lettuce, celery and many small flowers, actually needs light to germinate, so it goes on the surface and is only pressed in. Sowing small seed too deep is the most common reason a tray never comes up.

6. Keep the surface damp, and water from below

A seed that starts to germinate and then dries out is dead, and no amount of later watering brings it back. Keep the surface consistently moist until seedlings emerge, using a cover or a sheet of glass if the tray dries quickly. Once they are up, water by standing the tray in shallow water and letting it drain, which keeps stems drier and reduces the risk of damping off.

7. Feed the soil, and know your browns from your greens

Good compost is the cheapest improvement you can make to a garden bed. If you make your own, the balance to aim for is roughly equal parts by volume of carbon-rich "browns" and nitrogen-rich "greens".

• Browns are dry and carbon-rich: dry leaves, straw, shredded cardboard and paper, woody prunings, sawdust from untreated timber.
• Greens are moist and nitrogen-rich: grass clippings, kitchen scraps, fresh weeds, manure.

Grass clippings are a green, not a brown, which is a common mix-up. A heap that is all clippings goes slimy and smells; a heap that is all dry leaves sits there and does nothing for a year.

8. Light matters more than you expect

Long, pale, floppy seedlings leaning towards a window are not short of warmth, they are short of light. A sunny windowsill gives light from one side only, so turn trays daily, and move seedlings off any heat source once they have germinated. Warmth without light is exactly what produces weak, stretched plants.

If you use a grow light, keep it close, within roughly 5 to 15 centimetres of the seedlings for most LED units, and run it around 14 to 16 hours a day.

9. Harden off before planting out, and do it in the right direction

Seedlings raised indoors have never met wind, direct sun or a cold night. Put them straight into a garden bed and they stall or burn. Hardening off means increasing their outdoor exposure gradually, not reducing it.

Over about a week, start with an hour or two outside in a sheltered, part-shaded spot, then lengthen the time each day and move them into more sun and wind. Bring them in at night for the first few nights if it is cold. By the end of the week they should be outside all day and overnight, and ready to plant. Plant out on a still, overcast day or in the late afternoon rather than into the middle of a hot one.

10. Match the pot to the plant

A seedling in an oversized pot sits in more wet mix than its small root system can use, and that is a good way to rot it. Pot on in stages instead, moving up a size as roots fill the current container. Whatever you use, it needs drainage holes. Reused punnets are fine, just wash and dry them before the season starts.

11. Sow a little, often

Forty lettuces that mature in the same fortnight is a glut, not a harvest. Sow a short row or half a punnet every two to three weeks through the season and you get a steady supply from the same bed. This works especially well for lettuce, radish, rocket, beans and spring onions.

12. Label everything, and expect to lose some

Write the variety and the sowing date on a label at the moment you sow. You will not remember, and two punnets of brassica seedlings look identical. Keeping a simple note of what you sowed and when, and what worked, is how you get better each season faster than any book will teach you.

Some sowings will fail. That is normal, it happens to everyone, and it is usually one of the causes listed above rather than bad luck or bad seed.

Frequently asked questions

Why are my seedlings long and floppy?

Not enough light. Move them somewhere brighter or lower a grow light closer, and take them off any bottom heat once they are up.

Should I start seeds indoors or sow direct?

Root crops such as carrots, parsnips and radish resent transplanting and are best sown direct. Tomatoes, capsicum, chilli, brassicas and most flowers transplant happily and benefit from an early start indoors.

How long does seed stay good?

It varies a lot. Tomato and brassica seed keeps for years in a cool, dry, dark spot, while parsnip and onion seed is best bought fresh each season.

Do I need a greenhouse?

No. A greenhouse or cold frame extends your season and gives seedlings shelter, which is genuinely useful in cold districts, but a bright windowsill and a covered tray raise perfectly good seedlings.

My seeds did not come up at all. What went wrong?

Check four things in order: sowing depth, whether the mix dried out, whether the soil was warm enough for that crop, and how old the seed was. Those account for most failures.

Related growing guides

• A step by step guide to starting seeds indoors
• Sow to the Seed, Not to the Spade: How Deep Seeds Really Want To Go
• Stop planting seedlings straight from the windowsill
• Damping off: what it is and how to prevent it

Ready to plant? Browse our Vegetable Seeds, Herb seeds and Flower Seeds.