By Thomas D. Landis
Seed treatments before sowing
Milkweed seeds need to be rinsed in running water to clean away any fungus spores, so put the seeds in a small mesh bag or make one by using a paper punch to put holes in a small zip-lock plastic bag. Put the bag of seeds in the bottom of a pail and then just let water vigorously flow past the seeds and out the top of the bucket for about 30 to 45 minutes (Figure 1A). If you have just a few seeds, you can just do this in a pan in the kitchen sink and let the bubbling water run down the sink.
Native plant seeds, including many milkweeds, are dormant and require a cold, moist period before they can germinate; this exposure happens naturally during winter. Stratification is a nursery term that describes the combined use of moisture and cold temperatures to overcome seed dormancy. Sandwich stratification is the best procedure for small amounts of seeds. Use a single sheet of industrial paper towel or a stack of kitchen towels and moisten them completely. Drain off the excess water by vertically holding one end of the towel .
Then, place seeds one layer deep on 1/4 of the paper towel surface, spreading the seeds evenly across the moist paper towel so that they do not contact each other. This will help prevent the spread of mold to other seeds. Fold the paper towels over the seeds (Figure 1B), and place the sandwich into a clear, plastic zip-lock type bag and put them into a refrigerator. Check occasionally to ensure seeds are moist and not moldy. If mold develops, remove the sandwich, open it, and rinse the seeds under cool, running tap water. Wash out the zip-lock type bag with warm water and soap. Spread seeds onto a new stack of moistened paper towels, put the sandwich back into the bag, and refrigerate. Keep checking the seeds every week or so until they begin to germinate (Figure 1C).
Figure 1 - Milkweed seeds need to be cleansed in a running water rinse (A), and then stratified under cold and moist conditions (B). Seed should be sown after they just begin to germinate (C).
Sowing options for milkweed seeds
Direct seeding. You can plant milkweed seeds in the fall or winter so that they will undergo natural stratification before germinating the following Spring. It’s still a good idea to cleanse the seeds with a running water rinse before sowing, and then covering the seeds with the thin mulch. Milkweed seeds should be sown shallowly - less than ½ inch.
Sowing germinants. If you stratified your milkweed seed, you can just sow them as they germinate (Figure 1C). Place each germinant into Jiffy pellet (Figure 2A) or sow then directly into the soil and cover with a light mulch. Jiffy pellets allow young plants to be transplanted without damage to the root system.
Seed balls. These are a good option because they permit precise placement and protect the seeds from weather or predators. When placed in the Fall, allow for natural stratification. Make a mixture of clay and screened compost with enough water until it achieves a cookie dough texture. Adding a small amount of powdered mycorrhizal inoculum is a good idea (Figure 2B). Roll the mixture into small balls, make a dent and then add 2-5 milkweed seeds and reform into a ball. Plant the seedballs in the fall just below the soil surface and cover with a light mulch (Figure 2C). Water initially and then as needed until seedlings are established. You can purchase seed balls or ingredients from the following website or on Facebook: seedsinaball.com.
Figure 2 - Seeds can be sown in Jiffy pellets (A), direct seeding, or seedballs (B). Sown seeds or seeballs should be covered with a light mulch to protect seeds and conserve moisture (C).
Figure 1A
Figure 1B
Figure 1C
Figure 2A
Figure 2B
Figure 2C
