Cold Stratification & The Seeds That Love It

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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.)

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.

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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.)