• My account
  • Cart
    • Email
    • Facebook
    • Instagram
    • Pinterest
    • YouTube

The Coeur d'Alene Coop

Raising Chickens and Urban Gardening

  • Home
  • About Our Heirlooms
    • About Candace
  • Garden Consulting
  • Shop
    • NEW/RETURNING for 2025
    • NEW! Culinary Planters
    • NEW! Flowers
    • Grown from Organic Seed
    • Heirloom Tomatoes
    • Heirloom Peppers
    • Heirloom Vegetables
    • Cool Season Vegetables
    • Herbs
    • Container/Small Space
    • My Favorites!
  • CdA Coop Blog
    • Gardening
      • Soil and Compost
      • Garden Seed Series
      • Growing Tomatoes Series
      • Growing Garlic Series
    • Backyard Chickens
    • Recipes
    • Garden Glossary
      • How Often to Divide Perennials & Winter Care
      • Q/A Sheet: How to Decide What to Grow in Your Garden
      • Ripe for the Picking: A Quick List of Common Fruit and Vegetables to Ripen On or Off the Vine
      • Vegetable Plant Family Chart
      • Seed Starting Charts
  • Contact Us
You are here: Home / Gardening / Garden Seed Series / The Big Chill: How Cold Stratification Boosts Germination

January 3, 2025 By Candace Godwin Leave a Comment

The Big Chill: How Cold Stratification Boosts Germination

The transformation of a tiny seed into a thriving plant is nothing short of miraculous. Indeed, Nature holds the secrets to perfect timing, ensuring that a seed not only germinates but does so precisely when conditions are right for its survival.

Though we often think of seed planting as a simple act—sow, water, and wait—this intricate process relies on specific environmental cues. Temperature, moisture, and light are pivotal in signaling the seed’s awakening from dormancy.

tomato seedlings
Tomato seedlings need little more than warm soil, moisture, and light to germinate. But that’s not the case with all seeds.

For many seeds, the warmth and moisture of spring soil are enough to spark life. But some seeds require a cold, dormant spell before sprouting—revealing yet another layer of Nature’s magical design.

Cold Stratification: Ensuring The Time is Right

Have you ever wondered why Black-eyed Susan or Coneflower seeds fail to sprout when they hit the ground in the fall? Germination conditions are nearly perfect, yet they remain dormant.

The seed’s extended dormancy is caused by a germination-inhibiting hormone that prevents it from sprouting too soon. If they were to germinate in the fall, the seedlings would perish in the winter. It’s Nature’s way of ensuring the seed’s survival.

Many native and perennial flowers require a period of cold before they will germinate in the spring.

The hormone gradually dissipates as winter’s cold and damp conditions progress. Only after this cold period will the seeds break dormancy and germinate once conditions are favorable in the spring. This way of Nature ensuring the seed’s survival is known as cold stratification of seeds.

Chilling Out

It may surprise you to know how many perennial and native flowers, herbs, and even a few vegetable seeds require cold stratification for germination (or will have increased germination rates). The list below is not all-inclusive but provides a good overview.

Common Plants That Require Cold Stratification

  • Flowers: Black-eye Susan (Rudbeckia), Blanket Flower, Coneflower (echinacea), Chamomile, Goldenrod, Joe Pye Weed, Lobelia, Lupine, Milkweed, Pansies, Penstemon, Pincushion Flower (Scabiosa), Poppies, Primrose, Verbena, Yarrow
  • Herbs: Bee Balm, Catmint, Chives, Garlic Chives, Cilantro, Anise Hyssop, Lavender, Lemon Balm, Mint, Parsley, Rosemary, Sage
  • Vegetables: Artichoke, Asparagus, Hops, Strawberries

The recommended sowing time for many of these plants is in the fall. If you’ve tried growing these in the spring from seed or started them indoors and experienced poor germination, the reason was likely a lack of cold stratification.

Years ago, I learned this lesson the hard way with rosemary. Every attempt I made to grow the herb from seed resulted in little or no germination—a miserable failure each time. I questioned the seed’s viability. I questioned my skills as a gardener. Finally, I researched “how to grow rosemary” and discovered it required cold stratification. A lightbulb moment, for sure.

Unfortunately, few seed companies list cold stratification information on their seed packets, so I recommend researching “how to grow…” when starting unfamiliar seeds.

Methods of Cold Stratification

There are three ways to achieve cold stratification. The easiest is to let Nature take her course and sow seeds in the late fall for natural winter exposure. Once spring arrives, the seeds will readily germinate.

dried rudbeckia flower stalks in the garden
Rudbeckia seeds will naturally stratify over the winter and reseed.
You can also collect and dry the seed for cold stratification.
Seed can be directly sown in the garden in late fall to naturally stratify over winter.

With this method, wait until there’s been at least one hard frost before scattering the seeds over roughed-up soil and covering them with a thin layer of compost or finely chopped leaves.

Of course, sometimes Nature’s timeline doesn’t jive with the gardener’s. Suppose you can’t wait for seeds to overwinter in the garden, or you’ve forgotten to plan ahead and missed the fall planting window. In that case, winter sowing and refrigeration are two more ways to achieve cold stratification.

Winter Sowing Method

Winter sowing also capitalizes on winter’s cold, wet conditions for stratification, but here, seeds are planted in plastic milk jugs or other containers and placed outside.

In our region, this is often done in January and February, although seeds that require less time to stratify can be sown as late as March.

Winter sown seeds are planted in January or February.
Winter conditions will naturally stratify winter sown seeds.
Seeds will germinate in the spring when the time is right for them.

With winter sowing, there is no need to worry about frost dates or sowing timing; seeds germinate when the conditions are right, resulting in hardy seedlings that don’t require hardening.

In addition, this method can be used to sow many hardy annual flower and vegetable seeds that don’t require cold stratification.

Refrigeration Method

The most common way gardeners stratify seeds is through refrigeration. Most refrigerators hold seeds below 40°F, creating the perfect environment for chilling.

Seeds are placed in a damp paper towel or a small amount of moistened vermiculite or sand inside a plastic zip bag. The bag is not sealed completely, as the seeds need air.

rudbeckia seeds and dried seed heads
Collect and dry seeds in early fall.
Place seeds on a damp paper towel, inside a plastic bag, and then into the refrigerator.
Don’t fully seal the bag. Periodically check on the moisture of the towel.

The time spent chilling depends on the plant variety, ranging from a day to three months or more. For example, catmint seeds need very little time in the cold—about 24 hours in the freezer will do—whereas hops need up to three months to stratify.

Most seeds need about four to six weeks, but check the seed packet or search the plant’s required stratification period online.

Monitor moisture levels weekly; the towel or growing medium should remain damp but not overly wet. Once seeds go through their faux-overwintering, they will be ready to germinate. The seeds can be planted per the packet instructions for indoor seed starting or, if the timing is right, sown outdoors.

Winter’s Wonder

Cold stratification is a testament to Nature’s brilliance and resilience, ensuring that seeds awaken at the right moment to thrive. By embracing this process, you unlock the potential to grow native and challenging plants successfully (I’m looking at you, rosemary).

So, this winter, take some time to experiment with cold stratification and watch as your gardening efforts bloom into something extraordinary. Whether you’re a seasoned gardener or a beginner, this simple practice will bring a touch of magic to your garden and a sense of accomplishment to your green thumb.

Black eyed susans and coneflowers growing together in the garden

Filed Under: Garden Seed Series, Gardening Tagged With: chemical seed dormancy, cold dormancy, cold hardy vegetables, cold stratification, germination issues, germination process, native plants, perennial flowers, refrigerating seed, seed dormancy, seed stratification, stratification of seed, winter sowing

Get Garden Tips & More

« Winter Gardening: How to Grow Fresh Herbs Indoors All Season Long
Timing Is Everything: How to Plan Your Seed-Starting Schedule »

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Recent Posts from The Coop

  • How To Garden Without Pesticides: Natural Ways to Fight Pests May 2, 2025
  • Heirloom, Hybrid, GM-Oh My! Understanding These Gardening Terms April 18, 2025
  • Budget Gardening Hacks: Grow More for Less with These Simple Tips April 4, 2025

Search Our Plants Here

Shop by Category

Cart

the coop on facebook!

The Coeur d'Alene Coop The Coeur d'Alene Coop is at 2nd Street Chicken Ranch.

7 hours ago

The Coeur d'Alene Coop
Day #3 of plant pick up! Garage: full of plant orders. Greenhouse: full of plant orders. Garden: full of plants to be packed. Nine more days to go. Happy times for everyone! 🌻🌿🍅🌶🫑🥬🫛#thecoeurdalenecoop #heirloomvegetables #growyourownveggies #homegrownisbest #organicgardening ... See MoreSee Less

Photo

View on Facebook
· Share

Share on Facebook Share on Twitter Share on Linked In Share by Email

the coop on instagram!

The Coeur d Alene Coop

thecoeurdalenecoop

#thecoeurdalenecoop
@thecoeurdalenecoop
Heirloom tomatoes 🍅🍅
Organic gardening 🥕🌶
& Urban chickens! 🐔🐓

Day #3 of plant pick up! Garage: full of plant ord Day #3 of plant pick up! Garage: full of plant orders. Greenhouse: full of plant orders. Garden: full of plants to be packed. Nine more days to go. Happy times for everyone! 🌻🌿🍅🌶🫑🥬🫛

#thecoeurdalenecoop 
#heirloomvegetables 
#growyourownveggies 
#homegrownisbest 
#organicgardening
Load More... Follow on Instagram

Join the Flock!

Sign up to get gardening & chicken keeping tips delivered to your inbox.

Copyright © 2025 The Coeur d'Alene Coop · Coeur d'Alene, Idaho 83814 · Privacy Policy · Log in
Website Design: Godwin Marketing Communications LLC