The SeeddeeS® Winter Guide: Starting seeds indoors during the cold months
Why your garden already begins while it’s still cold outside. When the wind howls around the house and the last leaves have been cleared away, most gardeners think: “Let the garden rest until March.”But what if we told you that the real preparation for a blooming spring actually starts right now? Exactly: indoors!
With just a few simple steps, you can already awaken seeds during winter and that truly gives you a head start on the new gardening year.
Don’t want to forget anything? We’ve also brought all the steps together in a handy checklist, which you can download at the bottom of this blog via the link.
Why start seeds indoors in winter?
You might think: It’s too cold to grow anything.
Yet starting seeds indoors is the smart way to achieve longer growth, stronger plants and earlier harvests.
• You give your plants a head start before the real growing season begins
• Cold, diseased soil, frost and birds have no chance indoors
• You extend your gardening enjoyment — even during winter
Tip: Look at your seeds and your last frost date to determine when to start indoors.
(In our downloadable checklist, we guide you through this step by step.)
What do you need?
Before we dive into the technique, let’s cover the basics:
Good light source
In winter, sunlight is scarce. A sunny windowsill helps, but an LED grow light is even better — it gives your seedlings exactly the light they are missing.
Warmth (you may need it!)
Most seeds germinate best at around 18–24°C. In colder rooms, a heat mat under your trays can work wonders.
Light and air
Don’t just place your trays under light; make sure there is also ventilation so your seedlings don’t grow tall and weak.
Seed mix and pots (SeeddeeS®)
Use fine, airy seed-starting soil — not garden soil — and make sure your containers have drainage.
Step-by-step: How to sow indoors
(These steps can also be found clearly in our downloadable SeeddeeS® Winter Checklist.)
1. Choose the right seeds
Not all plants are ideal candidates for early indoor sowing. Some root vegetables and cold-loving plants are better sown later or directly outdoors.Good for indoors: peppers, tomatoes, herbs, some flowers and slow-growing vegetables – read here how to pre-sow tomatoes in winter.
Better later or directly outdoors: carrots, dill, coriander and parsley.
2. Fill and sow
Fill your tray with light seed-starting soil. Sow according to the instructions on the packet — thinner is better than too dense.
3. Water with care
Keep the soil moist, but not soaking wet. Light misting or bottom watering works best.
4. Warmth and light are key
Without enough light, most seeds won’t survive winter. Place your trays under grow lights or in a warm spot.
5. Label everything
It sounds simple, but you don’t want to forget what is growing where later on.
6. Wait patiently
Some seeds sprout within a few days — others take a bit longer. Patience pays off.
Get more out of your winter sowing project
Set up a grow light schedule
12–16 hours of light per day is ideal when daylight is limited. This encourages strong, healthy growth.
Ventilate your seedlings
Air circulation prevents mold and strengthens stems. Think of a small fan or letting in fresh air occasionally.
Hardening off: let them adapt
When spring finally arrives, plants can’t go straight outside. Let them gradually adjust to sun, wind and cooler nights.
Can it be even easier?
Yes! Some gardeners sow outdoors in mini greenhouses made from old milk cartons, a small winter-sowing ecosystem. This method is called winter sowing and lets nature do part of the work.
SeeddeeS® Winter Tip
Winter seed starting is not only practical; it’s cozy.
Place a tray on the table, make a cup of hot chocolate, and watch the tiniest sprouts begin their journey.
Want to keep everything easily at hand?Download the SeeddeeS® Winter Checklist for indoor seed starting here
Because your garden doesn’t begin outside.
It begins the moment you start dreaming about it.