In our article The Wonder of Seeds and Germination we discussed the different environmental needs of some seeds. In this article, we will share a more in depth look at Cold Stratification as well as specific varieties that should be stratified for optimal germination.
In nature, seeds require certain conditions in order to germinate. Seed stratification is the process where seed dormancy is broken in order to germinate. In order for the stratification of seeds to be successful, we create an environment to mimic the natural cycle. For cold stratification, we use coconut coir or sand, water and refrigerate.
Winter Sowing is the natural germination process. For this article, we are re-creating that environment in 4-6 weeks instead of several months.
At the bottom of the list, we've copied the instructions we originally shared in The Wonder of Seeds and Germination.
LIST OF HERBS TO COLD STRATIFY
Anise Hyssop
Angelica
Arnica
Bergamot / Beebalm
Betony
Butterfly Weed
Catmint
Catnip
Chamomile
Comfrey
Echinacea (purple coneflower)
Goldenrod
Larkspur / Delphinium
Lavender
Lemon Balm
Lupine
Marshmallow
Milkweed (Asclepias)
Mountain Mint (L)
Mugwort
Mullein
Phlox
Poppy
Ramps
Sage
Saint John's Wort
Self Heal
Skullcap
Stinging Nettles
Rosemary
Valerian
Verbena
Wild Strawberry
Yarrow
Artichokes
Cold stratification is an extremely easy process and once you’ve done it once, you’ll no doubt get the hang of it. The time you need to keep your seeds in the refrigerator depends on the variety, but 4-5 weeks should be a sufficient amount of time for most seed varieties.
Once there’s no more chance of frost in your area, take your seeds out of the fridge and plant as normal. The simple, quick process of cold stratification helps the seed germinate quicker and grow more readily in your garden bed.
DIY Cold Stratification
Coconut Coir or Sand & Water
- Place a 1/4 cup of coconut coir sand (or more) in a mixing bowl. Slowly add water until you can form a ball with the sand/water mixture.
- Add your desired seed amount to the sand. Mix thoroughly.
- Place sand/seed mixture in a ziploc bag or container and seal.
- Label the variety and date clearly on the bag.
- Place in the refrigerator for 4-6 weeks before planting. If seedlings start to sprout in the bag in the refrigerator, remove immediately and either plant in the ground or in pots until it’s time to plant outdoors.
6 comments
What about blueberries & other berries? Do they require up to 4 months? – should they be kept outside to simulate their growing/ winter conditions?
I would also like to know about sweet peas and nasturium since I have both to plant. Thanks
Mary what about vegetables I’ve done some with success., kalibos cabbage, squash with winter sowing in the milk jugs.
Can seeds that need cold stratification, just be put on damp paper towels and covered in fridg? Or do they need to be put in coconut coir or sand and water? What about sweet peas or nasturium? Thanks
Thank you for sharing your article on seeds that require stratification.
Can seeds, that need cold stratification, be stored (long term) in the fridge? I hadn’t seen this article, previously. I stored the seed packets in the fridge, over the winter, and recently sowed some indoor to start.