As spring approaches and the cold of winter wanes, gardeners all over start getting anxious about getting those seeds and seedlings in the ground to be ready for a beautiful flower garden or veggie patch. Last frost dates are noted, and research is done on what each type of seed needs to reach its full potential.

What Is Cold Stratification?

Many seeds, especially annuals, can simply be planted in the ground after the last frost of spring and have plenty of time to do their thing before the first frost of autumn rears its head. However, some seeds, especially native perennials, don’t always work this way. In particular, wildflowers that self-seed at the end of summer need their seeds to be shielded from frost and/or unseasonably warm spells that might trick seeds into germinating too early. These seeds go into a state of dormancy called cold stratification until they are ready to reemerge, on time, come spring.

Many people have started to see the benefits of growing native wildflowers in their gardens. Growing native wildflowers helps to promote local biodiversity and sustain populations of local birds and insects. Research has shown that some native trees can support the existence of hundreds of local creatures, while imported non-natives might support only a small handful. Some butterflies are often on the hunt for specific flowers to feed on and lay eggs on, and with the depletion of natural habitats and green spaces, this is proving a challenge.

In a bid to start giving back to the land, gardeners, both seasoned and amateur, hunt seed packets filled with wildflowers mixes, echinacea, milkweed, black-eyed-Susans, or St. John’s wort. With all the good intentions in the world, some seeds will have very low germination success without having been through cold stratification. While seeds that have fallen to the earth directly from their parent plant the previous year will experience this cold stratification naturally, seeds from a seed packet won’t have and need a little helping hand.

Luckily, this cold stratification process is something that can be fairly easily replicated.

How Can I Cold Stratify My Perennial Seeds?

Source: Growit Buildit/YouTube

If you have some perennial wildflowers seeds that you want to see sprout in the spring, you have two options. You can sow your seeds at the beginning of winter, safe in the knowledge that your seeds experience the depths of cold weather and naturally cold stratify. However, if spring is already approaching and your seeds are still in the packet you bought them in, there is a way to force this process.

There are two ways you can recreate this process. One is by using sand, and the other is by using a paper kitchen towel. The paper towel method is the overall easiest method as it works for all sizes of seeds. Some of the tiniest seeds will get lost in the sand, and it will be impossible to retrieve them.

  • Paper Towel Method: Take a square piece of paper towel and dampen it with a spray bottle of water. You don’t need to saturate the towel, just moisten it. Next, on one-quarter of the towel, sprinkle your seeds. Don’t go more than one layer deep with your seeds. Fold the paper towel around your seeds so that they are enveloped. Put the paper towel into a ziplock bag and label it with the type of seed you have inside and the date. Next, pop the bag into the fridge for 4-6 weeks.
  • Sand Method: This is a good method for larger seeds that can easily be picked out of the sand come planting time. Put some sand into a pot and spray it with water. The sand should be moistened entirely but not so wet that the sand will not clump together in your squeezed hand. Next, put a good handful of sand into a ziplock bag and add in your seeds. Make sure that the seeds are completely covered by the sand. Close the bag, label it with the variety of seed and the date, and pop it into the fridge for 4-6 weeks.

After the cold stratification process is over, you can plant the seeds according to the instructions on the seed packet. This process will greatly improve the germination rate of certain varieties of perennial plants, especially native wildflowers. Use this method, and you will have yourself a beautiful garden that will delight you and the pollinators!

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