You can get much better germination with some vegetable and flower seeds if you put them through a period of cold before planting them.
If you're having trouble germinating certain seeds it might be because you're doing every single thing right - except this one thing. Cold stratification is a period of chilling and it might be exactly what you need for your persnickety seed.
It's especially helpful if you missed the window for plants that like to be planted when it's still cold outside.
The difference it makes is amazing. This spring I experimented with chilling and not chilling a few different types of seeds including Bells of Ireland. The seeds that weren't chilled did nothing. They didn't even attempt to sprout.
The chilled seeds sprouted with an almost 100% germination rate. That's the difference a bit of cold can make.
🌱 Most seeds that require cold stratification want:
- Moisture (to simulate winter snow or damp soil)
- Cold (typically fridge temps, 1–5°C / 33–41°F)
- Time (usually 2–6 weeks depending on the plant)
And the standard method is:
- Dampen a paper towel (moist, not dripping)
- Fold seeds inside
- Place it in a labeled airtight container (jar, zip bag, etc.)
- Refrigerate
This keeps seeds from drying out or molding, and it lets the moisture + cold combo trigger germination enzymes.
Table of Contents
Plants That NEED Cold Stratification
(Without it, they probably won’t germinate at all.)
| Plant | Chill Time + Notes |
|---|---|
| Bells of Ireland | 7–14 days — Moist fridge. I did 10 days—worked great. |
| Milkweed (Asclepias) | 30 days — Moist fridge. Monarch magnet. |
| Lupines | 3–4 weeks — Moist fridge. Nicking seed coat helps. |
| Columbine (Aquilegia) | 2–4 weeks — Woodland classic. Cold makes it cooperative. |
| Delphinium | 2–4 weeks — Moist & dark fridge. |
| Pasque Flower | 4+ weeks — Moist fridge. |
| Lavender | 30 days — Moist fridge. Chill wakes it up. |
| Penstemon | 30–60 days — Moist fridge. |
| Echinacea (Coneflower) | 4 weeks — Moist fridge. Cold jumpstarts stubborn seeds. |
| Blue Flax | 3–4 weeks — Moist fridge. Cold breaks dormancy. |
| Joe-Pye Weed | 30+ days — Moist fridge. Native, but picky. |
Plants that BENEFIT From Cold Stratification
(Cold = optional but helpful. Like preheating your oven.)
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SWEET PEAS
Soak seeds for 12–24 hours to soften the seed coat then chill in a damp paper towel inside a sealed container in the fridge for 5–7 days.
Or: Just direct sow into cold, early spring soil and nature will take care of it. Maybe.
Learn how to grow them on a teepee made out of bamboo sticks.
SNAPDRAGON
1–2 weeks fridge, moist or early outdoor sowing.
You can see the variety in this list of the flowers and vegetables I grow.
POPPY
Any period of cold will improve germination and vigour. Poppies need LIGHT to germinate. Don't cover.
You can try the ice cube method.
CELERY
1–2 weeks fridge, moist. Cold triggers better, faster germination.
HELIOTROPE
2–4 weeks fridge, moist. Otherwise germination is painfully slow.
ORACH
5-7 days fridge, moist. Or sow in cold early spring soil.
When I first tried to grow Orach I could NOT get it to germinate. I guess this is why. I didn't know it needed cold.
BELLS OF IRELAND
1–2 weeks cold + moist. Without it, they’re incredibly finicky.
Stick them in the fridge. Forget them. Then plant like someone who’s done being bossed around by a tyrannical botanical narcissist. (Not Narcissus. He’s fine.)
Marguerite Roberts
Spinach! The allotment garden won't let us in till May 1st. By then, it's just too warm for spinach & lettuce. Do you have a cunning plan??!? Yes. I do have a fridge, and even a freezer.
Karen
I mean, the only cunning plan I can come up with is to plant the seed before the allotment closed last fall. 😆 ~ karen!
Norma
Marguerite, this is exactly what I do too - I leave a few spinach plants at the back of my garden to go to seed and then, after the fall clear-out, sprinkle them all over every available dirt surface. They're the first things to pop up in the spring and can be harvested just before you put your plants in the ground for the summer. It works well for me every year, no matter the weather!
Marguerite Roberts
Well, I can sure try that. I suspect that whatever spinach comes up may have bolted by the time they let us in there May 1st since there's plenty of warm weather in late April. In the two previous mild winters I did have volunteer pole beans at the alottment garden, incredibly. My taters also overwintered in a raised bed in my home garden and came up again two springs in a row. I was all set to plant dahlias in that bed then we got that near frost at the end of April. A week later up sprouted the taters. In 50 years of gardening I've never seen that. I will definitely try fall planting of spinach, though. I didn't think that was possible in this part of Canada. I'm originally from Manitoba so am still saying "Ya mean I can grow This? ..and this?! ..and This?!" after 40 years in Ontario.
Karen
Hi Marguerite! I have volunteer potatoes come up every single year. That just means I'm really bad at digging them all up in the fall. ~ karen!
Rachel
Winter sowing. It’s da bomb! Sow in January in milk jugs of soil and let nature take care of all the rest.
Karen
Hi Rachel. Yes! It's amazing. ~ karen!
Randy P
I don't do 'farming', but I did share this great info with my FB family and friends. My ex is a life-long avid gardener.
Karen
Thanks for sharing it Randy! ~ karen
Linda
What is the ice cube method? That link did not work. I have lots of poppy seeds and the perfect spot for them, if they will grow. Please share your wisdom.
Karen
The ice cube method is coming up later this week! ~ karen!
Ann
I have gardened for close to 60 years. When the internet came along it because my best gardening companion.
Even for things I have grown over and over, I look on the internet to make sure I remember everything that will help me be successful with it this year. What conditions to help it grow it's very best. I am growing a couple of new things this year and one of them, Ridolphia, needed darkness to sprout. Had I not looked up and found that out, I might have failed.
Things to look up: how to best germinate, preferred soil temps, sun exposure, soil structure such as well drained vs moisture retaining, preferred soil ph. There are so many things, that few of us can remember everything there is to know for every plant we grow.
So take my advice all, and take the time to refresh your memory every year, for every plant you grow
carla
Huh! Thank you! I didn't know poppies could benefit from cold stratification. Perhaps that is why I've had no luck scattering California poppy seeds here in California. Once a seed takes hold, the plants will self seed, but I've had a heck of a time getting them started. The link for the ice cube method is 'not found'....
Karen
Crud! Thanks I'll check it. ~ karen!
Karen
Wowzers thx so much have tried Belles of ireland so many time with no luck 🍀. Also have sprinkled literally 1000’s of poppy until i tried the ice cube method