As winter lingers and outdoor soil remains cold and uninviting, savvy gardeners across the UK are already growing — indoors.
Starting seeds inside is a brilliant way to get ahead of the season. Whether you're a first-time grower or a green-thumbed veteran, this guide from Yorkshire Seeds will walk you through everything you need to start seeds indoors successfully and with confidence.
Why Start Seeds Indoors?
Indoor sowing helps you:
Get a head start on spring crops
Extend your growing season
Grow healthy, hardy transplants
Save money on buying young plants
Sow varieties that need a longer growing period (like chillies & tomatoes)
It’s also a brilliant way to stay connected to your garden during the colder months — and there’s something magical about watching fresh green shoots emerge on your windowsill!
🗓️ When to Start Sowing Indoors
Start by checking your local last frost date (usually around late March to early May in the UK, depending on region). Then count backwards from the transplanting time for each plant.
🪴 What You’ll Need
You don’t need fancy equipment to get started. Here's a basic checklist:
Essential Seed-Starting Supplies:
Seed trays, modules, or small pots
Seed compost (light and fine-textured, ideal for germination)
Yorkshire Seeds early-start seed varieties
Plant labels or markers
Clear plastic covers or a basic propagator
Spray bottle or watering can with fine rose
Sunny windowsill or grow light
🌿 TIP: Avoid heavy garden soil—it compacts easily and can carry pests or diseases.
- 📚 Step-by-Step: How to Start Seeds Indoors
1. Prepare Your Containers
Clean seed trays or modules with warm, soapy water if reused. This helps prevent diseases like damping-off.
2. Fill with Compost
Use a fine seed-starting mix. Fill containers and gently level off the surface. Avoid compacting the soil too much.
3. Sow Your Seeds
Follow the spacing and depth guide on the seed packet. Some seeds just need a light covering of compost, while others prefer light exposure to germinate.
🌱 TIP: Sow extra seeds as not all may germinate — especially for herbs and chillies.
4. Water Gently
Use a spray bottle or fine-rose watering can. The soil should be moist but not soggy.
5. Cover & Warm
Cover trays with a propagator lid, plastic dome, or cling film. Place somewhere warm (18–21°C) — a windowsill, shelf above a radiator, or a heated propagator works well.
6. Light is Life
Once seedlings emerge, they need plenty of light. Use a south-facing window or install grow lights. Rotate trays daily to prevent leggy growth.
7. Ventilate & Harden Off
As seedlings grow, remove covers for part of the day to let in air. Before transplanting outdoors, harden off by gradually introducing them to outdoor conditions over 7–10 days.
🌿 Great Crops to Start Indoors Now
Here are some of our favourites for indoor sowing in early spring:
Tomatoes – especially heritage or cherry types
Peppers & Chillies – need a long growing season
Basil, Parsley, Thyme – perfect for a windowsill herb garden
Salad Leaves – fast-growing and delicious
Leeks & Spring Onions – easy to grow in modules
Broccoli & Cabbage – great for early transplanting