Many perennials have a hard coating that helps protect the outer shell from breaking and sprouting too early. We’ve all experienced an unseasonably-warm spell in the middle of January or February — this mechanism helps prevent the seeds from being tricked into coming out of dormancy until it’s just the right time. The natural cold stratification needed for germination can be forced with just a few materials, water, a refrigerator, and patience.
Cold Stratify Seeds: Gather Materials
Cold stratification is an extremely easy process and once you’ve done it once, you’ll no doubt get the hang of it. The first step is to gather the materials needed, all of which can be found in your home, tool shed, or with a quick trip to the hardware store.
Materials for Cold Stratification:
- Seeds
- An all-purpose sand mixture and/or Peat Moss
- Paper Towels
- Water
- Plastic Ziploc bags
- A Sharpie for labeling
- Mixing containers or bowls
- Refrigerator or cold room
Sand and/or Peat Moss/Water Method
- Place a 1/4 cup of sand or peat moss in a mixing bowl. Slowly add water until you can form a ball
- Add your desired seed amount to the mix.
- Place the mixture in a Ziploc bag and seal. Shake the seed around inside the bag to mix the seed with your mixture.
- Label the variety and date clearly on the bag.
- Place in the refrigerator for 1 month 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.
Paper Towel Method
- Soak your seeds for 1-2 hours.
- Strain the seeds using a mesh filter, paper towel, or coffee filter.
- Spread seeds out in a single layer on the paper towel.
- Wrap a dry paper towel around the damp paper towel to help keep things moist but not too wet (which could become moldy).
- Place in a Ziploc bag and seal.
- Label the variety and date clearly on the bag.
- Place in the refrigerator for 1 month 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.
COLD STRATIFY SEEDS: PLANTING
The time you need to keep your seeds in the refrigerator depends on the variety. Most varieties should take about 4-5 weeks. Once there’s no more chance of frost in your area, take your seeds out of the fridge and spread seed on bare soil as normal. The simple, quick process of cold stratification helps the seed germinate quicker and grow more readily in your garden bed.
