Starting your own seeds indoors is where real gardening begins — it's cheaper than buying plants, gives you varieties you'd never find in a shop, and gets you a head start weeks before it's warm enough to sow outside. Watching those first seedlings appear on the windowsill never gets old.
Whether you want to grow tomatoes, chillies, or a tray of salad, here's how to start seeds indoors and raise strong, healthy plants.
What you'll need
- Containers with drainage — seed trays, or upcycled egg cartons, toilet roll tubes, yogurt pots, or milk jugs
- Seed compost (finer than potting mix)
- Seeds, water, and a warm, bright spot
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- Fill containers with moist seed compost and firm it gently.
- Sow at the depth on the packet — tiny seeds barely covered, bigger ones deeper.
- Water gently with a fine mist or from below, so you don't wash the seeds out.
- Keep warm — most seeds germinate best in gentle warmth, so a warm windowsill or a propagator helps.
- Cover loosely with a clear lid or bag to hold humidity until they sprout, then uncover.
Light is everything
The moment they sprout, seedlings need bright light or they turn tall, pale, and floppy. A south-facing windowsill (turned daily) or a grow light keeps them stocky and strong.
When to start seeds indoors
Timing is everything: sow too early and seedlings go leggy waiting for warmth outside; too late and you lose the head start. The simple rule is to count back from your last expected frost date using the seed packet:
- Tomatoes, chillies, peppers, aubergines: 6-8 weeks before last frost (they need the longest run).
- Brassicas and most flowers: 4-6 weeks before.
- Salad and fast greens: 2-4 weeks before, or sow in succession.
If you do not know your last frost date, a quick local search will tell you — it is the single most useful number for planning a growing year.
Growing on
Thin out crowded seedlings and keep the strongest, pot them into bigger containers as they outgrow their cells, and start feeding once they have their first true leaves.
Harden them off
About a week before planting out, put the seedlings outside for a few hours a day, increasing the time gradually, so they acclimatize to wind and cooler air. Skipping this step shocks them.
What to start indoors
Tomatoes, chillies, peppers, aubergines, basil, salad, brassicas, and many flowers all do well. Grow them on into containers or beds once the weather warms.
Sowing on your windowsill? Share your seed-starting setup in the comments at ecoxee.com — grow lights and jam-jar propagators welcome.
Keep reading: No-Dig Gardening for Beginners, A Beginner's Companion Planting Guide, and Composting for Beginners: How to Start.
