This Is the Best Way to Germinate Seeds Outside in Winter.
Sure, we’ve just locked up the garden for the winter , but within a few months you’ll be starting to grow seeds again. Some of these seeds require cold stratification , which exposes the seeds to low temperatures. People usually simulate this cold temperature cycle by leaving the seeds in the refrigerator, but you can free up space in the refrigerator by simply leaving the seeds outside, since a cold refrigerator is meant to simulate winter anyway. I’ve seen various ways to do this using empty milk containers, buckets and ice cube trays, but I recently came across a method from an Instagram gardener that I believe is much better.
If you watch how plants grow in the wild, where plants drop seeds in the fall and then grow again in the spring, you will realize that these seeds are exposed to rain, snow and cold temperatures during the winter. It’s not just that they survive this cold; some seeds literally need a cold wind to germinate in the spring. Temperatures up to 39–40 ° F are sufficient for this process, so few environments do not reach this range in winter. While there are no hard and fast rules about which seeds require this cold treatment, most flowers and herbs do, although some perennials, such as asters and nasturtiums, and some annuals, such as zinnias, do not. While most vegetables don’t do this, some, like peas and artichokes, do. While there are many lists of herbs and flowers that require stratification, none are exhaustive. However, you can often find this information on the seed package or simply search by plant name and “cold stratification.” It’s safest to assume that your perennial flowers and herbs actually need it.
In some cases, the seeds you buy in the spring may already have been cold stratified, but this is usually not the case. So for years, gardeners have been simulating this cold by using a refrigerator, and it is certainly a controlled experience—the refrigerator is kept at one temperature at all times. On the other hand, you can simply throw the seeds on the ground in the fall and let nature take its course, but this exposes the seeds to other threats such as wind, birds and other wildlife.
My favorite method is cold stratification of seeds outdoors.
But this method , featured by a gardener named Elizabeth on the appropriately namedWintersowing Instagram account, takes the best of both worlds by creating a semi-controlled environment outside for the seeds. What I like about this method is that it requires little equipment and all the materials can be reused. At a basic level, you sow a handful of seeds into potting soil in a Ziploc bag with drainage that is lifted off the ground and held upright. The seeds experience all that winter has to offer and will begin to germinate on their own when the weather is right. You can then carefully separate the sprouts and replant them. This method means that the seeds have been exposed to and survived the actual environment and weather they will grow in, meaning the germinating seeds are more resilient to your growing situation. They do not require hardening as they are grown outdoors; In spring, you can simply transplant the seedlings into the ground.
You’ll need one bag for each variety of seed you’ll be growing: Using gallon-sized ziplock bags with a slider , cut a few small slits in the bottom of the bag, as shown in this video . This is for drainage. Mark the bag (most zipper bags have a window for this) with a permanent marker. Add a few cups of potting soil and moisten the soil so it is moist, not soaking wet. You can squeeze the bag to get rid of excess water. Holding the bag upright, add the seeds to the surface of the soil. The seed package will indicate how deep the seeds should be planted, and you should still follow these directions. For example, if they say the seeds should be an inch deep, sprinkle them and then add another inch of soil on top to cover them.
You’ll need to find a place to put the bags – the space between two raised beds is ideal for this, but you can also build one using paving stones or bricks. You need two walls about a foot high that you will hang the dowels from. In her Instagram videos, Elizabeth uses marshmallow sticks instead of dowels, which can be purchased in a kit.
The bags should be left slightly open to allow rainwater and snow to get in, but should not be left completely open. Elizabeth zips the bags almost all the way up, leaving a few inches open at one end. A clothespin is attached to this end of the bag. She then slides the first dowel through the zippered end of the bag, near the top. The second dowel is laid parallel to the first, next to the other end of the bag, and the clothespin is attached to the dowel and then to the bag, effectively attaching the bag to the dowel. You can see the finished result in this post .
Leave your bags to check the weather
Regardless of whether they are covered in snow or frozen, the seeds should be fine. What should germinate will germinate in the spring . Elizabeth shows how her seeds experience the weather in her garden under a variety of conditions. The only thing you need to check is that the bags remain upright and are exposed to air through the opening in the bag.
The zippered bag acts like a tiny greenhouse, trapping moisture and temperature. In that sense, it’s a very effective place to grow your sprouts, although they will obviously outgrow their temporary digs. Most flower seedlings should survive direct transplanting from bags into soil outside. Remove the entire clump of soil from the bag that will be held together by the roots of the seedlings, and then carefully break the clump into individual plants and plant them in the ground. The bags, dowels and clothespins can be saved to be used again next year.