A lot of people are surprised to find that seeds require special treatment in order for them to germinate properly. Many times, we must replicate what happens in nature to ensure proper sprouting. This is called cold stratification.
What is seed stratification?
Cold stratification is imitating the natural dormancy period a seed would experience in nature during the winter months in order to promote proper sprouting.
Basically, you're simulating a natural process to make the seed think it's safe to come out of the ground.
Do all seeds need cold stratification?
The requirement for cold stratification often comes as a surprise when reading over the seed packet and seeing "requires 2 to 7 weeks of cold treatment before planting". Uh... the seed catalog didn't tell me that?
So, you skip over it, plant the seeds anyway, and the results are less than spectacular.
That being said, obviously, not all seeds require this special treatment. But, when they do require it, they require it. You'll be disappointed in the growth if you just try plopping them in the ground. At least... until next spring.
Deciduous and evergreen perennials, many cold hardy herbs, wildflowers, and even some cool season biennials can benefit from cold stratification.
Seeds that require cold stratification
- Fruit trees that require chill hours (ex. apples, peach, cherry)
- Deciduous trees (ex. oak, walnut, maple)
- Poppies
- Columbines
- Echinacea
- Milkweed
- Lavender
- Verbena
- Catmint
- Oregano
- Anise Hyssop
- Butterfly Bush
How to Cold Stratify Seeds
Now that we know some seeds require cold stratification, you'll be happy to know that it's a very easy process to accomplish.
For small seeds, such as those of a wildflower, you will simply wrap them in a moist (not sopping) paper towel, put them in a baggie, keep the baggie open, and set them in the back of your refrigerator.
For larger seeds that will be a bit easier to locate, you can moisten some coconut coir or peat, put them in it in a zipper bag, leave the bag open and place it in the back of your refrigerator.
You'll want to keep the paper towels or the coconut coir moist, but not sopping and you'll want to make sure that it's getting plenty of fresh air and not growing mold.
I pull my bags out every couple of days, inspect them for mold, and let them get a bit of fresh air before I put them back in the fridge.
I place my seeds in the very back of the top shelf of our refrigerator (that's the coldest spot in ours).
Once you've cold stratified long enough, you can plant your seeds in the seed starting mix. Once they reach the ideal temperature, they will sprout believing spring has, indeed, sprung and it's their time to shine.
Dry seed stratification
While most seeds do best with moist treatment and it's ideal for almost all varieties we homesteaders grow, if you're like me and short on time... you can try dry seed stratification.
This is simply taking that packet of seeds, putting them in the refrigerator, and waiting until planting time. Sometimes this method works fantastic, sometimes... not as much, but if you don't want to fuss with paper towels and coconut coir and maintaining finicky seeds... go for it.
How long to stratify seeds
The length of time for cold stratification is going to vary based on the variety. Many times, the information is located on the seed packet, if it isn't, study the particular plant to get a general idea of how long.
A good rule of thumb for most seeds is going to be 4 to 6 weeks. But, that's just a general rule... not cut into the stone. The hardier the plant is, the longer they need cold treatment.
Outdoor Stratification
You can also stratify seeds in the great outdoors. To do this, though, you need to start in the fall.
You can either place them in a pot, cover them with some coconut coir, and put them in a shady location, or alternatively, you could put them in the garden.
If you put them directly in your garden, I recommend planting them as late in the fall as you can and using row covers so they don't get eaten.
If you put them in a pot and have a random warm day, you'll have to either put the pot in the refrigerator or put it in a cold garage, etc.
With this method, you'll still have to occasionally water it if it starts to get a bit dried out and watch for mold...
As long as we know what we are dealing with, those seed packets aren't so confusing, right? Cold stratification is really pretty simple, just need to plan in advance so we have enough time to make those seeds happy so we have a happy garden!
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Susu says
Finally found to way to start echinacea germination. Thanks 👍🌷
Danielle McCoy says
Glad you found it helpful! Have fun growing echninacea!