Starting seeds indoors in spring is genuinely one of the best things you can do on a balcony or patio. You'll get far more variety than buying plug plants, save a decent amount of money, and there's something rather satisfying about watching something grow from a tiny seed. If you've got even a small windowsill or shelf, you can make this work.
Getting Your Light Right
Most edible plants need at least 6 hours of direct sunlight daily, and in the UK a south-facing windowsill or balcony will give you the most light. If your space only gets 3–4 hours of direct sun, don't worry — leafy greens like lettuce, spinach, and herbs like parsley will still thrive in partial shade.
If you're serious about seed starting but your space is shaded, an LED grow light running 14–16 hours daily replaces natural sunlight entirely. It sounds fancy, but honestly, even a modest setup makes a real difference.
Doing It on a Budget
You don't need expensive equipment. Repurpose yoghurt pots, egg cartons, or old plastic takeaway containers — just poke a few drainage holes in the bottom. Make your own seed compost by mixing peat-free compost with a bit of perlite or garden sand. You'll spend a fraction of what bagged seed compost costs.
Collect rainwater in a bucket or butt if you can — it's better for your seedlings than tap water and completely free. When it comes to seeds, choose a collection like the Pronto Herb & Vegetable Seed Collection, which gives you 1,700+ seeds across 21 varieties for around £10. That's exceptional value compared to buying plug plants.
Container and Compost Basics
Use pots that are at least 5–7cm deep for most seedlings. A pack of mini terracotta pots costs around £10 and will last you years. Always use proper seed compost or potting mix rather than garden soil — garden soil compacts and drains poorly, and seedlings hate that.
Fill your containers to about 1cm below the rim, water gently until moist (not soggy), then sow your seeds at the depth stated on the packet. A pack of bamboo plant labels for £5–6 is a small investment that saves you guessing which container holds which seeds three weeks later.
The Mistakes That Catch Everyone Out
Overwatering is the biggest killer. Seedlings need moisture, not waterlogging. Let the compost dry out slightly between waterings — use a fine mist spray bottle rather than pouring from a watering can, which drowns them. If you see yellow leaves, check your drainage first; overwatering causes this far more often than nutrient deficiency.
Leggy, pale seedlings stretching upwards mean they're reaching for light. Move them closer to your window or add a grow light. And here's a practical tip: don't start twenty different varieties at once. Pick two or three — perhaps tomatoes, courgettes, and basil — and nail those before expanding. Spreading yourself too thin is how things get neglected.
Troubleshooting Common Problems
If seedlings suddenly look weak or droopy, it's almost always a watering issue. Check that your pots have drainage holes and that compost isn't waterlogged. Aphids can appear on new growth — a strong spray of water blasted from a mist bottle usually shifts them without chemicals. If you're growing tomatoes and spot dark patches on the bottom of fruits (blossom end rot), it means inconsistent watering. Keep the compost evenly moist, not feast or famine.
Getting Started This Spring
The key is to focus on the fundamentals. Use a container with proper drainage, fill it with peat-free potting mix, place it where it gets the most available light, and water carefully. Keep a notebook or phone notes app to record what you've planted, when you sowed it, and germination dates — this becomes invaluable for planning next year. Most of all, don't overthink it. Seed starting is forgiving once you understand these basics, and honestly, you'll get better results than you'd expect on your first attempt.