Starting seeds indoors is genuinely one of the best things you can do on a balcony, patio, or windowsill. You'll save money compared to buying plug plants, access far more varieties than your local garden centre stocks, and there's something deeply satisfying about watching something grow from a tiny seed. Spring is absolutely the right time to begin, especially if you're new to it.
Making the Most of Your Available Light
Light is the biggest factor in successful seed starting indoors. Most edible plants need at least 6 hours of direct sunlight daily. If your balcony or patio faces south, you're in luck—that's where the strongest light lands in the UK. East or west-facing spaces work too, though you'll get fewer hours. North-facing? Don't worry. Leafy greens like lettuce, spinach, and herbs like parsley are genuinely content with partial shade and just 3–4 hours of sun.
If natural light is genuinely limited where you are, a seed starting tray with built-in LED lights is a practical investment. Run it for 14–16 hours daily and your seedlings will thrive indoors regardless of season or location.
Start Cheap, Scale Up Later
You absolutely don't need fancy equipment. Yoghurt pots, egg cartons, or even toilet roll tubes work perfectly as seed containers—just drill or poke a few drainage holes in the bottom. Small terracotta pots hold about 50ml and are ideal for individual seedlings without taking up much space.
For compost, buy a good peat-free blend like Westland multi-purpose and stretch it further by mixing in perlite or coarse sand. You'll improve drainage and save money. Collect rainwater in a bucket or butt instead of using tap water—plants prefer it and it costs nothing.
Seeds are dramatically cheaper than plug plants. A multi-pack herb and vegetable seed collection costs around £10 but gives you 1,700+ seeds. One packet of tomatoes or courgettes costs £2–3 and produces far more plants than you'd ever buy as plugs.
The Mistakes Everyone Makes (And How to Avoid Them)
Overwatering kills more seedlings than anything else. The soil should be moist but never waterlogged. Let the surface dry slightly between waterings—use a fine mist spray bottle for delicate young seedlings rather than pouring water on them.
Never use garden soil from outside. It compacts easily, drains poorly, and carries pests and diseases. Potting mix is designed to stay light and fluffy. Similarly, containers that are too small restrict root growth and force you to water constantly. A 7–8cm pot is plenty for most seedlings.
Leggy, thin seedlings stretching towards the light tell you they're not getting enough brightness. Move them closer to a window or add supplementary light. Yellow leaves usually mean either overwatering (check drainage first) or nutrient deficiency—a balanced liquid feed sorts that out quickly.
Keep it Simple at First
Start with just one or two crops. Basil, lettuce, and parsley germinate reliably and grow quickly—perfect confidence-builders. Once you've got a seedling or two thriving, you'll feel ready to expand. Label everything with bamboo plant labels so you don't forget what's what. It sounds obvious, but losing track of which pot contains which variety is surprisingly easy.
Container size matters for your space. A south-facing windowsill might hold 15–20 small pots comfortably. A balcony corner could fit a proper seed tray or two. Work within what you've actually got room for rather than cramming everything in and spreading your attention too thin.
Water carefully with a small indoor watering can, pinch herbs regularly once they've got a few true leaves to encourage bushiness, and don't be afraid to move pots around if something isn't thriving in its current spot. Most of this is just common sense paired with a bit of trial and error—and that's where the learning happens.