Growing Milkweed and other Asclepias from Seed

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Perennial Asclepias seeds need to go through a cold stratification period. Cold stratification is very important for the germination and growth of Milkweed, Swamp Milkweed and Butterfly Weed. It mimics natural winter conditions a seed must go through in order to break the seeds dormancy cycle. Stratification is a cold, moist time period that triggers the seed’s embryo to grow and expand. This will break through the now softened seed coat and go in search of sun and nutrients. Nature spreads the seeds in fall by wind. The seeds land on top of the soil, sit there all of winter freezing and thawing, moist and dry, and then germinate in spring. The natural freezing and thawing of the soil creates little cracks in which the milkweed seeds get wedged in. We need to mimic nature to germinate the seeds. Several ways:

1. Scatter seeds where you want them directly in the garden in late fall. Do this late enough so they do NOT germinate until spring as temps warm the soil.

2. Plant the seeds in pots outside in late fall/early winter. Place pots on ground in a protected location from winter wind but somewhere where it will be exposed to rain, snow and cold. In spring, move pots to a sunny location and keep moist if spring is very dry. Seeds should sprout when soil warms.

3. Mimic nature by chilling the seeds yourself in spring. Lay seeds on a moist paper towel and place inside a Ziploc bag. Place in the refrigerator for 45-60 days. Once this process is finished, plant 1-2 seeds in a cow pot 2/3rds filled with seed starting soil. Add a pinch of granular kelp, sprinkle soil on top and lightly press down. Place cow pots in a water proof tray and add water to the tray to water from the bottom up. This prevents fungus. Add just enough water so soil looks damp. Never allow pots to sit in standing water. Place tray on a heat mat with a dome cover and they should germinate in 7-10 days. After most of the tray has germinated, take dome cover off and place in bright window or under a grow lamp. Seeds need plenty of light and warmth now. Turn trays if seedlings lean toward light and “pet” your plants to mimic wind daily for stronger stems. Water in ½ strength organic plant magic every 2 weeks until planting in the ground.

After chance of frost is well past us and the ground has warmed, transplant the seedlings outside when they are 3-6” tall, in the cow pot so the roots are not disturbed. Place the tray outside in the shade for a week before planting in the ground. Try to plant on a cool or cloudy day so the plants have a chance to acclimate. Milkweed does best in a sunny, open area. Water after planting and then only once a week at most for a few weeks, then stop. Milkweed does not like supplemental water once established. Be sure the entire cow pot is under the soil and add an inch of mulch to the garden bed around the seedlings. If it looks like the plant dies-it may be going through shock. Do not worry—after a couple of weeks, it should sprout new leaves. The first season, the plant will not flower. The second season it may!

In an effort to provide horticultural information, these educational documents are written by Nancy DuBrule-Clemente and are the property of Natureworks Horticultural Services, LLC. You are granted permission to print/photocopy this educational information free of charge as long as you clearly show that these are Natureworks documents