Q. I ordered some seeds and noticed on some of the packets the planting instructions called for stratification. What is this and how do I do it? – Alistair M.
A. Stratification is a mechanism that mimics the natural process that most perennial seeds go through before they can germinate. If the seed immediately germinated, then the growing conditions would not be ideal for the plant to survive. The period of dormancy assures that the seeds will be viable come warmer weather and better growing conditions. Most native perennial plants will set their seed and then the seed goes through a period of dormancy. If left to its own, the seed would go through a fall and winter season with cold and moist conditions.
The easiest method of stratification is to direct sow your seeds. This method is considered a natural stratification as it simulates what would happen in nature without any human intervention. Sow your seed in late fall or early winter on a weed-free site. Then monitor for moisture and watch for germination as spring approaches.
The cold-moist method is by far the most common form of stratification. This treatment uses a growing medium and your refrigerator. A paper towel, coffee filter, or sand can serve as a growing medium. You will also need resealable plastic bags or containers. Check the seed packet to see how long your seeds need to be cold and moist. Then begin the stratification process that many days before you want to sow your seeds.
The coffee filter or paper towel method works best if you are planting the seed cells or containers. Soak the seeds briefly to ensure they are moist. Drain the seeds into a fine-screened sieve lined with a paper towel or coffee filter. Be sure to allow the seeds to drain well, otherwise the seeds will rot. The paper should be moist but not soggy. Remove the paper towel or coffee filter from the sieve and arrange the seeds in a single layer. Carefully fold the paper and place it in a resealable plastic bag or sealable plastic container. Label with the start and end date. Place the sealed bag or container in a spot in the refrigerator that maintains 33 to 41 degrees. The deli
drawer is an ideal spot. Check the container weekly to make sure the paper has not dried out or is too soggy. After the required number of days has elapsed or if you see that the seeds are beginning to sprout, plant immediately in seed cells or containers.
If you plan to sow your seeds in rows outdoors use the sand method. Again, as with the coffee filter method, calculate the day you should start stratification. Put about 1/3 to ½ cup of fine sand into a bowl and add a small amount of water. Start with two teaspoons and add small amounts to the sand so that you can form into a ball. Add about 1/8 ounce of seed, more or less, depending on the size of the seed and mix with the sand. As with the paper towel/coffee filter method, place the sand ball in a plastic bag or plastic container and refrigerate. Be sure you label it with the start and end date. Check weekly and be sure the sand does not dry out. Once the number of days of stratification is complete, plant in your prepared rows. If seeds germinate more quickly than you expect, plant in containers and grow indoors until spring and then plant when the chance of freezing has passed.
Be sure to check the seed packet or research the stratification requirements before you buy your seeds. Many native seeds require the cold-moist method as detailed in this article. Some seeds need light after their stratification. Further, a small number of seeds such as those in the Callirhoe family of poppies or Ceanothus americanus, New Jersey Tea, require a hot water treatment before the cold moist method. Some seeds need two periods of cold-moist stratification, such as Arisaema triphyllum, Jack-In-The Pulpit and Ilex verticillata, Winterbery Holly. They can take up to two years to germinate. So, again, check the seed packet to ensure success in starting your perennials.
In our area we are lucky to have a long growing season, so even if you start stratification now you should be able to raise your seedlings to maturity. If the stratification requires over 90 days, you will probably have better success by waiting until this fall to sow the seeds in the outdoors where they will undergo the damp and cold that they need and germinate next spring.
If all else fails, there are two plant sales at the Carroll County Ag Center where you can find a wide selection of plants ready to put in your garden. The West Georgia Chapter of the Georgia Native Plant Society plant sale is on April 18. On that same day, and just a short walk from the plant sale, the Master Gardener’s Art in the Garden is at the Buffalo Creek Demonstration Garden. The other plant sale that you don’t want to miss is The Master Gardener Mother’s Day plant sale on May 9.
If you have more questions about horticultural issues, contact a Master Gardener Extension Volunteer at the UGA Cooperative Extension Carroll County Office at 900 Newnan Road in Carrollton at 770-836-8546 or via email at ccmg@uga.edu.
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