Starting seeds indoors is genuinely one of the best things you can do on a balcony, patio or windowsill. You get far more variety than buying plug plants, save a fortune, and there's something deeply satisfying about watching seedlings grow from tiny specks. Spring is the perfect time to begin, so let's walk through how to do it properly without overcomplicating things.
Light is Everything
Most edible plants need at least 6 hours of direct sunlight daily. South-facing windowsills and balconies in the UK get the most light, especially from March onwards. If your space only gets 3–4 hours of direct sun, stick with leafy greens and herbs—they're far more forgiving in partial shade.
If natural light is limited, don't panic. A simple seed starting tray with LED grow lights will do the job without breaking the bank. Run it for 14–16 hours daily and your seedlings will thrive regardless of the weather outside.
Budget-Friendly Setup
You genuinely don't need fancy equipment. Start seeds in recycled yoghurt pots, egg cartons, or newspaper pots—just drill drainage holes in the bottom. Make your own potting mix by combining peat-free compost with perlite and sharp sand; it costs a fraction of ready-made bags. Collect rainwater in a bucket or water butt—it's better for plants than tap water and completely free.
Buying seeds rather than plug plants saves you 70–80% on costs, especially if you're growing multiple plants. A multi-variety seed collection gives you options without the commitment of buying individual packets.
The Most Common Mistakes (And How to Avoid Them)
Overwatering is the single biggest killer of seedlings. The compost should feel moist but not waterlogged—let it dry out slightly between waterings. A fine mist spray bottle is brilliant for this; it gives you precise control without drowning your seedlings.
Never use garden soil—it compacts, drains poorly, and often carries disease. Stick with proper seed compost or multi-purpose peat-free compost. Use containers at least 5–7cm deep so roots have room to develop; anything smaller and you'll be watering constantly.
Start small. Pick two or three varieties you actually want to eat—basil, lettuce, and courgettes are reliable choices. Trying to manage 10 different varieties at once is exhausting and most won't get the attention they need.
Spotting and Fixing Problems
Yellow leaves usually mean overwatering or a nutrient deficiency. Check drainage first—if water pools on top, you're watering too much. Once seedlings are a few weeks old, a diluted balanced feed helps.
Leggy seedlings (tall, pale, stretching towards the light) mean insufficient light. Move them closer to a window or get a grow light. This usually fixes itself within days.
Aphids can appear on soft new growth. A strong spray of water from a watering can usually blasts them off. Blossom end rot on tomatoes is caused by inconsistent watering—keep moisture levels even and it stops.
Getting Started the Right Way
Set up your workspace with the basics: proper containers with drainage, quality compost, and the best light source you can manage. Water in the morning so foliage dries before evening (this prevents mildew). Label your pots as you sow—use a bamboo plant label set so you remember what you've planted.
Keep a simple watering schedule. Check your seedlings daily but only water when the top centimetre of compost feels dry. Most failures happen because people either drown their seedlings or neglect them entirely.
Start with one tray this year, see what works for your space and routine, then scale up next spring. You'll have fresh herbs and vegetables by early summer, and you'll know exactly how they were grown. That's the real reward.