Starting seeds indoors is the key step that gives you a head start on the whole season. Tomatoes, peppers, cucumbers and many other crops need this warm indoor start in Central Europe because the outdoor season is simply too short for them. With strong, well-grown seedlings you'll be harvesting weeks earlier than from seed sown direct outdoors.
When to start
Each crop has its optimal sowing time. Starting too early leads to leggy, weak seedlings. Starting too late means losing precious time.
- Peppers and chillies — mid-February (they need the longest growing season)
- Tomatoes — early to mid-March
- Cucumbers and courgettes — mid-April (they grow fast and dislike being moved)
- Cabbage, kohlrabi, cauliflower — March
- Lettuce — March to April (can also be sown direct outdoors)
What you'll need
The basic kit for starting seeds indoors is simple and inexpensive:
- Seed compost — a specially formulated fine compost with low nutrient levels. Don't use ordinary garden soil — it's too heavy and may contain pathogens.
- Seed trays or containers — seed trays, module trays or recycled yoghurt pots (with holes in the base). For pricking out, 8–10 cm pots.
- A clear cover — cling film or a plastic lid to retain moisture during germination.
- A spray mister — for gentle watering without disturbing the compost surface.
Sowing step by step
Fill the seed tray with compost to a depth of about 5 cm. Gently firm it and water it thoroughly. Allow excess water to drain away.
Spread the seeds on the surface 2–3 cm apart. Press gently and cover with a thin layer of compost — about 0.5 cm for tomatoes and peppers; for fine seeds (lettuce) simply press them lightly onto the surface. Mist gently with the spray bottle.
Cover the tray with film or a lid and place somewhere warm. The optimal germination temperature for most vegetable crops is 22–25°C. Don't place the tray directly on a radiator — overheating will damage the seeds. A table next to a radiator or a high shelf works well.
After germination
As soon as the first seedlings appear (3–10 days depending on the crop), immediately remove the cover and move the tray to the brightest spot you have. Lack of light is the single most common cause of leggy, weak seedlings.
Lower the temperature after germination to 18–20°C. Cooler conditions combined with plenty of light encourage compact, sturdy growth. Ventilating the room is important — fresh air reduces the risk of damping off disease.
If your windowsill faces north or east, consider supplementary lighting. LED grow lights cost very little and dramatically improve seedling quality. Run them for 12–14 hours a day.
Watering seedlings
Keep the compost evenly moist but never wet. Overwatering causes damping off — a fungal disease that topples seedlings at soil level. Water from below: stand the tray in a shallow dish of water for 10–15 minutes, then pour away any excess. Or use the spray mister.
Pricking out
When seedlings have produced their first true pair of leaves (not the seed leaves — the first "real" jagged leaves), it's time to prick them out into individual pots.
Prepare 8–10 cm pots filled with seed or all-purpose compost. Carefully ease a seedling out with a pencil or small fork, and hold it by a leaf (never by the stem — the stem is fragile). Make a hole in the new pot, lower in the seedling and gently firm the compost.
Plant tomatoes and peppers deeper than they were sitting — right up to the seed leaves. Roots will form on the buried portion of stem and the plant will be stronger. Cucumbers and courgettes dislike disturbance — sow them direct into individual pots from the start.
Hardening off
Two weeks before the planned planting-out date (around 1 May), start hardening off the seedlings. Initially put them outside in a sheltered spot for 2–3 hours — out of direct sun and wind. Gradually increase the time outdoors and the exposure to sunlight.
A seedling transplanted straight from indoors to outdoor conditions without hardening off will go into shock — leaves will scorch in the sun, stems will snap in the wind. The one or two weeks spent hardening off is an investment that pays back many times over.
Common problems
Leggy seedlings — insufficient light. Add supplementary lighting or move closer to the window. Leggy tomato seedlings can be planted deeper at pricking out.
Damping off — a fungal disease caused by overwatering and poor airflow. Water less, ventilate more. Preventively, you can dust the compost surface with a thin layer of vermiculite.
Yellow leaves — nutrient deficiency. Seed compost is intentionally lean so it doesn't scorch young roots. After pricking out, start feeding every 10 days with a diluted liquid fertiliser (half the recommended dose).
Starting seeds indoors is a skill that improves with practice. Every season teaches you something new. Don't be disheartened if the first attempt isn't perfect — even professional growers started with weak, struggling seedlings.