Growing milkweed plants from seeds by Thomas D. Landis
1. 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
a tea ball. Put the bag of seeds in pan in the kitchen sink
and let the cool water bubble through the seeds for about
30 to 45 minutes (Figure 1A) and down the drain.
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
Figure 1A
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. The idea is “moist,
but not wet”.
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 1B
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 a couple of months,
or when they begin to germinate (C).
2. Sowing options for milkweed seeds
2.1 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.
2.2 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.
2.3 Seed balls. These mixtures of clay and compost protect the seeds from weather or
predators. When outplanted in the Fall, seed balls 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 to 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: http://seedsinaball.com/.
Figure 2A
Figure 2B
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 2C
3. Other tips - Plant in
sunny locations. Milkweed plants can spread by rhizomes, so growing them in raised beds or
large containers is best. Irrigation during the first season isn’t absolutely necessary but will
results in larger, healthier plants. If you aren’t going to collect seeds, clipping the wilted flowers
will keep the plants blooming later in the season. Clipping seed pods (“follicles”) before they
mature will prevent milkweed seeds from blowing all over.