Growing herbs indoors on a balcony, patio, or windowsill is genuinely one of the easiest wins for a beginner gardener—and spring is absolutely the right time to start. Shop-bought herbs wilt in days; ones you've grown taste fresher and cost a fraction of the price. But I've seen plenty of people kill their seedlings within weeks by making the same handful of mistakes. Here's what actually works, from someone who's been there.
Get the Light Right
This is the big one. Most herbs and edible plants need at least 6 hours of direct sunlight daily. In the UK, a south-facing windowsill or balcony is your golden ticket—you'll get the strongest light there. If you're working with a north or west-facing space, don't panic: leafy greens like lettuce, spinach, and coriander cope fine with 3–4 hours of direct sun, though they'll grow slower.
If natural light is genuinely limited, a simple LED grow light running 14–16 hours a day will replace sunlight entirely and costs far less than you'd think. Position it about 15–20cm above your seedlings and adjust as they grow.
Choose Containers That Actually Drain
The second mistake is using containers without proper drainage holes, or filling them with a potting mix that holds too much water. Waterlogged roots kill more indoor plants than anything else—root rot sets in fast and there's no fixing it once it starts.
For herbs on a budget, terracotta pots are reliable: they're porous, affordable, and you can pick up small terracotta pots in packs of 10 for under £12. Make sure each one has at least one drainage hole at the base. For a slightly hands-off approach, self-watering planters work brilliantly for herbs—they keep moisture consistent without you obsessing over watering frequency. The reservoir sits beneath the soil and releases water as needed.
Use a good peat-free compost (most garden centres stock it now), and if you're reusing old compost, refresh it with fresh material—tired compost compacts and drains poorly.
Don't Neglect the Third Mistake: Inconsistent Care
Once seedlings are established, consistency matters more than perfection. Yellow leaves usually signal overwatering or a nutrient shortage—check drainage first, then water less frequently. Leggy, stretched seedlings mean they're reaching for light: move them closer to your brightest window or add a grow light.
Pests like aphids do sometimes appear indoors, especially near windows. A quick blast with a mist spray bottle removes most of them before they spread. A fine mist spray bottle is worth having anyway—it's useful for humidity and damage-free watering of delicate seedlings.
Practical Habits That Actually Work
- Pinch herb seedlings regularly (once they have 4–6 leaves). This stops them flowering too early and forces branching, so you get bushier plants with more harvestable leaves.
- Harvest from the top down—snip the stem tips to encourage side shoots. Never strip a plant bare in one go.
- Group pots together on your windowsill. They create a slightly warmer, more humid microclimate that seedlings actually prefer.
- Label everything with bamboo plant labels as you sow. You'll forget what's what within a month, I promise.
- If using self-watering planters, let the reservoir empty occasionally—it prevents salt buildup that can stunt growth over time.
Start with resilient herbs like basil, parsley, coriander, and mint. They're forgiving, fast-growing, and genuinely transform what you can cook with. Once you've cracked those, branch out to leafy greens. Spring is the perfect window to get going—you've got the light, the warmth is coming, and you'll be harvesting in 4–6 weeks.