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The Great Milkweed Germination Test

The Great Milkweed Germination Test

Tips for Growing Milkweed from Seed 

One of the best ways to attract monarch butterflies to your garden and help reverse their declining numbers is to plant milkweed.  In addition to providing nectar for numerous other species of pollinators, milkweed is the host plant for monarchs.  This means milkweed provides the baby food for baby butterflies (caterpillars).  Since a hungry monarch caterpillar increases its body mass about 2000 times as it grows, the more milkweed you have, the better!

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Growing milkweeds from seed is a great (and economical) way to add more of these critically needed plants to your landscape and perhaps even produce some extra seedlings to share with friends.  While there are 73 species of milkweed in the United States, the founder and director of Monarch Watch, Dr. Chip Taylor, states “about four of these species – Asclepias incarnata (swamp milkweed), Asclepias syriaca (common milkweed), Asclepias tuberosa (butterfly weed) and Asclepias viridis (green antelope horn) – sustain 98% of the eastern population of monarchs.”

Sow True Seeds currently offers three of these species, butterfly weedcommon milkweed and swamp milkweed. Many butterfly habitat gardeners, including Nina Veteto of the Asheville based nonprofit organization, Monarch Rescue, report that monarchs typically prefer to lay their eggs on the common milkweed.

One of Sow True Seeds’ local seed producers, Kim Bailey from Fruitland, NC, conducted an experiment this spring to test different stratification times and techniques before sowing common milkweed seeds. Stratification is a process of treating seeds prior to sowing in order to trigger or improve germination.  Kim has been an avid butterfly gardener for over 20 years and knows what has worked for her in the past, but was curious to test other methods.

As an environmental educator, she also wanted to create a model science investigation for the teachers she works with.  Kim used dry milkweed seeds (as you’d receive in a packet of seeds you purchased) for the control group.  For the variables, she mixed milkweed seeds with damp vermiculite and stored them in the refrigerator for 4, 6, and 8 weeks.  She also stored packets of dry seeds in the refrigerator for 8 weeks and one in the freezer for 8 weeks.  In addition, she put a set of seeds stored in damp vermiculite in the freezer for 8 weeks.  Finally, she tried storing seeds wrapped in a damp paper towel in the refrigerator for 8 weeks.  Kim planted 50 seeds from each group on March 14, 2015. Seeds were sown in 5 rows of 10 per container, then lightly covered with soil, and placed indoors under grow lights.

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Here are the initial results, just 1 week after sowing …

buy milkweed seeds for monarch butterflies from Sow True Seed

And the final results, 2 ½ weeks after sowing …

buy milkweed seeds for monarch butterflies from Sow True Seed

Clearly, cold-moist stratification in the refrigerator (whether seeds were stored in damp vermiculite or a damp paper towel) for 4-8 weeks, produced the best germination results.  As with most experiments, the results often generate more questions.  Kim is now interested in testing whether or not milkweed seed can be successfully pre-stratified then stored dry (and for how long?) then successfully germinated. 

As of early June, some of these same tiny milkweed seedlings that were transplanted into larger containers are now about a foot tall.

Incidentally, the parent plants that produced these seeds in the fall of 2014, were visited by a monarch butterfly who flew all the way from Mexico to lay 96 eggs on their leaves on April 22, 2015.

buy milkweed seeds for monarch butterflies from Sow True Seed

OK, do you need any more motivation to plant milkweed, than this?! The eggs were then collected and distributed to local teachers and other educators to rear and release.

Kim kept just two eggs that completed their life cycle from egg to caterpillar to chrysalis to adult over the next month and were released over Memorial Day weekend, under the very curious and careful watch of her pup, Mason!


Simple Steps from Packet to Plant


You’ve got all excited and order your seeds. They arrive. You are excited all over again.


You need to stratify your seeds. Here you have two options:

  1. If you are early enough in ordering your seeds, you can trust to nature and sow your seeds in early spring and let the natural cold period break the dormancy of the seed.
  2. If you are too late (the weather has warmed up) or you think mice, rats, rabbits, birds, tornadoes, floods and drought will get to your seeds then you can ‘force stratify’ your seeds. In this case you can see from Kim Bailey’s experiments that you will get the best germination if you stratify your seeds in the refrigerator for eight weeks, either folded into a wet paper towel or mixed in with damp vermiculite.


If you went natural then wait and see. Milkweed will begin to grow as it warms up. If you artificially stratified then you’ll want to plant the seeds once you remove them from the fridge. You can either direct sow them at this point, or you could plant them in pots and transplant later (as Kim Bailey chose to do).


Now it is up to the Monarchs!

Good luck to you and the butterflies


Article Written by: Angie Lavezzo

About the Author: Angie Lavezzo is the former general manager of Sow True Seed. Beyond her professional role at Sow True, Angie's passion for gardening extends into personal hands-on experience, fostering plants and reaping bountiful harvests.