How to Cold Stratify Milkweed Seeds in 5 Steps

The Monarch butterflies will soon be leaving their overwintering grounds in Mexico and start their epic journey North! Last year, they started to leave en masse around March 5th. Historically, they start to arrive in Nebraska in late May-June. That means that it is important to have mature milkweed plants for the Monarchs to lay eggs on when they arrive! I like to cold stratify my Milkweed seeds now so that I can plant them indoors by the beginning of April, and move them outside in May. This will give them ample time to grow large enough to feed the monarch larvae. You can purchase your milkweed seeds here.

Materials Needed: - 1 Qt Ziploc Bag - Sharpie - 10-20 Milkweed Seeds - A paper towel

Step 1: Dampen a paper towel and lay it on a flat surface.

Run the paper towel under the faucet, and gently wring it out so it is damp but not dripping with water. Too much water may cause the seeds to mold inside the bag.

Step 2: Sprinkle milkweed seeds evenly on paper towel It is best to sprinkle the seeds on one side of the paper towel so that when you fold it over, the seeds don't overlap.

Step 3: Fold paper towel into quarters

This will allow the paper towel to fit nicely inside the bag.

Step 4: Place paper towel into Ziploc bag, seal, and label. I like to label the bag with the common name, scientific name, and when I put the bag into the fridge. It may be a good idea to set a reminder on your phone so you don't forget about them.



Step 5: Place the bag into the fridge for 30-60 days. Find a place in your fridge where they won't be disturbed or crushed. I like to put the bag into a tupperware container. The ideal temperature for the seeds is 33–38°F. *If seeds start to sprout, remove immediately and place in soil near a sunny window. If the seeds begin to mold, compost and try again! I have found that this cold/wet stratification period increases the germination of my milkweed seeds. It is also a great activity to do with children to teach them about the life cycles of native plants. Stay tuned for the next blog on 'How to Start Milkweed Seeds Indoors'.


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