Planting Common Milkweed for Optimal Germination

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We started our milkweed garden in 2017 with the hope of attracting Monarch Butterflies to our garden. In the first season our milkweed took off and we raised about 20-25 monarch butterflies. After that season we were hooked and started planting common milkweed in other parts of our garden with the hope of attracting more butterflies.

Common Milkweed can be easy to grow from seed but it can also be a challenge. It can be a challenge because milkweed requires cold stratification to break dormancy. If you want to direct-sow milkweed seeds into your garden the best time to plant your seeds is in the fall. If you are planting milkweed seedlings you will want to plant them in the spring after the danger of frost has passed.

For a fall sowing scatter your milkweed seeds in your garden, press them into the soil and walk away. For winter planting, we have found great success in planting the seeds in milk jugs. And then transplanting the seedlings into the garden in the spring.

Once you find the method that works for you and your garden you will have great success in planting milkweed and attracting butterflies to your garden. Let’s dive into the details of how to plant milkweed seeds in your garden, but first why is milkweed important?

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Why Plant Common Milkweed

Common milkweed (Asclepias syriaca) is a native herbaceous perennial that appeals to butterflies—especially the monarch butterfly. Asclepias is the only plant family that serves as the host plant for monarch butterfly egg laying. The monarch larvae, the hatchling caterpillars, feed exclusively on milkweed leaves. Without milkweed, there can be no monarch butterflies.

When should common milkweed be planted?

Plant seedlings in the early spring after the danger of frost has passed and direct-sow seeds in the ground in the late fall.

Most native milkweed seeds require cold stratification in order to germinate and grow into healthy plants. What does that mean?

Cold Stratification is a cold, moist period that breaks seed dormancy. In nature, this process occurs in winter, keeping seeds from germinating until conditions are more ideal in the spring. Milkweed and other perennials (plants that live for several years) are more likely to require cold stratification. Cold stratification is very important for the germination and growth of native milkweeds.

Without prolonged exposure to cold temperatures, your milkweed seed is unlikely to sprout. In the wild, seed dormancy is usually overcome by the seed spending time in the ground through a winter period and having its hard seed coat softened by frost and weathering action. By doing so the seed is undergoing a natural form of “cold stratification”.

How Far Apart Do You Plant Common Milkweed?

Plant common milkweed about 18 inches apart; their rhizomatous roots will quickly fill in the space between plants. Your biggest maintenance challenge will probably be in containing them.

Learn More About Containing Milkweed by reading HERE.

3 Ways to Plant Milkweed Seeds

Fall Sowing

If you live where it freezes in the winter, late fall is a good time for direct sowing milkweed seeds outdoors. The benefit is that nature provides the winter conditions needed to stratify the seeds and expose them to cold and moist conditions. The alternating freeze and thaw of winter helps break down the seed coat and starts the growing process. Once the sun comes out and the ground is warm in the spring, the seeds will germinate on their own.

  1. Prep the soil by removing all existing growth and debris, 2-3 weeks before planting
  2. Plant your milkweed seeds just after the first frost
  3. Scatter seeds on the bare ground
  4. Compress the seeds into the soil with your hands or by walking on the seeds
  5. Do not cover the seeds with soil, they need light to germinate
    Water the seeds to set

Winter Sowing

Winter sowing is another method that allows Mother Nature to cold stratify milkweed seeds. Winter sowing is the process where seeds are sowed outdoors in the winter, typically in milk jug, or any other plastic container with a lid. The plastic containers act like a mini greenhouse and prevent the seeds from drying out and protect the seeds from hungry critters. Winter sowing works best in USDA Zones 4-8.

  1. Collect and wash milk jugs (discard the cap)
  2. Drill 5-6 ½” holes in the bottom of the milk jug
  3. Slice the jug in half right below the handle, leave the handle attached!!
  4. Pack 2”-3” inches of wet soil in the bottom of the milk jug
  5. Scatter seeds on top of the soil and compress the seeds into the soil wit your hand/finger
  6. Tape the jug back together with duct tape
  7. Label the jug
  8. Set jugs in a sunny spot. Rain and snow will enter through the cap hole creating condensation. Spray with water if dry. (the jugs become a greenhouse)
  9. Open the jugs in the spring to transplant into your garden. Once seeds have sprouted if you have opened the jug protect your seedlings from frost.

Spring Sowing

If you want to wait until spring to plant your seeds you will need to be sure that you cold stratify your seeds inside the refrigerator for at least 45 days. The simplest is to put seeds in moist soil or peat and store in an old refrigerator. If you don’t want soil in your refrigerator, you can also layer seeds between moist paper towels in a plastic container or Ziploc bag in your crisper, keeping them cold for a minimum of three weeks and up to three months.

  1. Dampen a paper towel with water and pour milkweed seeds into the middle
  2. Fold the seeds into the wet paper towel
  3. Place the paper towel with seeds into a container
  4. Place the container in the refrigerator for 4-6 weeks

You can get a head start and plant the seeds indoors in containers after they have been cold stratified in the refrigerator. Milkweed seeds can be direct sown in spring, but transplants have better success. Fill pots or trays with light, well-drained soil. I strongly suggest using Pro Seed Starting Mix that contains MYCOACTIVE, a proprietary formula to stimulate vigorous growth. Add the seeds and press down onto the soil. You do not need to cover the seeds but if you do, do so with just an eighth of an inch of soil. Keep soil moist and pots in a sunny, warm spot or under grow lights until the seeds germinate.

The seeds will take approximately 10 days to germinate. Once there are four true leaves on the seedlings (the seedlings will be approximately three inches tall), the plants can be transplanted into your garden once the danger of frost has passed.

Most milkweed species do best in full sunlight, so choose an open area with lots of sun so clear a patch in a sunny spot, giving each plant plenty of room to spread its roots. Water frequently until your plants are established.

Does Milkweed Need to Be Planted Every Year?

Milkweed should be planted/transplanted in the spring. It is a perennial and will come back every year but the plant will need all year to prepare for the coming winter. Milkweed planted in the fall will likely not survive the winter.

Are you ready to dive into the world of Raising Monarch Butterflies? Then you need the Raising Monarch Butterflies Guide! It will walk you through every step of raising Monarch Butterflies and help you troubleshoot problems along the way.