Winter sowing is one of the best-kept secrets in the garden — and once you try it, you'll wonder why you ever waited until spring.
How it works
Seeds are sown into mini outdoor “greenhouses” — think repurposed milk bottles or clear takeaway containers — during the coldest months of the year. The seeds sit outside, exposed to natural freeze-thaw cycles, and germinate exactly when conditions are right, just like they would in nature.
No coaxing. No timing guesswork. Nature handles it.
Why it works so well
- Many seeds actually need cold stratification to germinate — winter sowing gives them exactly that, naturally
- Seedlings grown this way are tough from day one — no hardening off needed
- You free up precious indoor space and windowsills
- It’s low-maintenance — nature does most of the work
- You get earlier, stronger plants than waiting for a warm spring day
How to get started
- Grab a clear container with a lid — milk bottles, takeaway containers, or salad boxes work perfectly
- Add a few centimetres of potting mix
- Sow your seeds, water lightly, and seal the lid
- Pop it outside in a spot that gets some light and rain — and wait 🌧️
- Check in spring — you’ll be amazed at what’s sprouted
A note on germination rates
Sometimes seeds can be slow to sprout — or germination rates lower than expected — and that’s completely normal. A few things that can affect it:
- Seed age and storage — seeds stored in warm, humid conditions lose viability faster. Keep them cool, dark, and dry.
- Soil temperature — many seeds won’t germinate until the soil reaches a certain warmth. Cold stratification helps some, but others need heat to trigger germination.
- Sowing depth — tiny seeds need light to germinate and shouldn’t be buried. A light press into the surface is all they need.
- Moisture levels — too wet and seeds can rot; too dry and they won’t wake up. Aim for consistently moist, not soggy.
- Patience — some varieties are naturally slow. Give them time before writing them off. 🙏
If you’re getting patchy results, try sowing a few extra seeds per cell to improve your odds, and don’t be afraid to resow if nothing’s happened after 4–6 weeks.
Not ready to winter sow? No worries!
If you missed the autumn window — or you have seeds that are raring to go right now — sowing indoors under heat or on a warm, sunny windowsill is a brilliant option. A heat mat makes a huge difference for warmth-loving varieties.
A useful tip: keep pinching seedlings back as they grow. It might feel counterintuitive, but it encourages bushier, more robust plants that will reward you come spring. 🌸
Don’t forget to harden off! Unlike winter-sown seedlings — which are already tough from being outside — indoor-raised seedlings need a gradual introduction to the outdoors. Start with an hour or two on a mild day, then slowly increase their outdoor time over one to two weeks before planting out. This prevents transplant shock and sets them up for success.
A quick note on scale
This method is perfect for home gardeners and small-scale growing — and we absolutely love it for that! If you’re running a larger garden or growing as a cut flower farmer, there are other approaches that might suit your scale better. Check out our guide to winter sowing at scale for more on that. 👇
Ready to get sowing?
Browse our range of seeds perfect for winter sowing at chbotanics.co.nz — and if you have questions about which varieties suit your conditions, we’d love to hear from you. 🌱
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