How to Winter Sow Milkweed in 7 Easy Steps
If you want to grow milkweed from seed, winter sowing is one of the easiest methods. Join farmer and native plant enthusiast Briana Yablonski to learn how to winter sow milkweed in a few easy steps.

Contents
When I talk to others about native plants, milkweed is one of the first plants new gardeners mention. This genus of plants has stepped into the spotlight in recent years due to its ability to support dwindling monarch butterfly populations and feed other pollinators.
If you want to add a few butterfly-attracting plants to your garden, starting from seeds is one affordable and easy option. However, it’s important to know that many milkweed seeds need exposure to cold before they can germinate. That’s why winter sowing is a great option for milkweed.
If you’re unfamiliar with winter sowing or have questions about the details, keep reading. I’ll cover the basics of this seed-starting practice and explain how to use it to grow healthy flowers.
What is Winter Sowing?

Winter sowing involves planting seeds outdoors during the winter. This process is ideal for seeds that require a period of cold stratification before they can germinate. After the seeds experience the cold required to break dormancy, they’ll germinate when the weather warms.
You can practice winter sowing by sprinkling seeds directly on the ground or planting seeds in small containers that mimic greenhouses. The latter is often preferred for small gardens since it helps keep seeds moist and protects tender seedlings from the cold.
When Is the Best Time to Winter Sow Milkweed?

The goal of winter sowing is to expose your seeds to the cold temperatures necessary to break dormancy. The necessary cold stratification period varies between milkweed species and various geographic populations, so not all seeds require the same amount of cold exposure. In fact, some species will germinate without any cold stratification.
However, there’s no harm in exposing them to cold temperatures. So, if you’re not sure how much cold exposure your specific species requires, aim to expose them to at least four weeks of temperatures before 40°F (4°C).
No matter where you live, you can winter sow milkweed seeds in December or January. If you live in a colder growing zone, such as zones 3-6, you can also sow in February or early March. The goal is to ensure they receive at least a month of temperatures below 40°F (4°C).
Obtaining Seeds

If you don’t already have milkweed seeds on hand, it’s time to get some. You can either purchase seed packets or collect seedheads from mature plants. The best time to collect them is in the late fall when you notice the pods are dry.
Many people think butterfly weed is a single plant, but this genus of plants (Asclepias) actually contains hundreds of species, many of which are native to North America. I recommend choosing a species that’s native to your area and well-suited to thrive in your garden’s sun exposure and soil moisture.
Here are some popular types of milkweed for North American gardeners.
- Showy milkweed (Asclepias speciosa): This milkweed is native to the western United States and produces round clusters of light pink flowers. It thrives in full sun and moist soil.
- Common milkweed (Asclepias syriaca): Native to the eastern half of the US, common milkweed sends out wide, oblong leaves and spherical clusters of pink flowers. It can thrive in disturbed sites and poor soil but prefers full sun.
- Butterfly weed (Asclepias tuberosa): You may also hear people call this plant pleurisy root, butterfly flower, or orange milkweed. It produces large, flat clusters of bright orange flowers and thrives in full sun.
- Swamp milkweed (Asclepias incarnata): As its name suggests, swamp milkweed requires moist to wet soil. It can tolerate full sun or partial shade and is native to the eastern US.
- Narrowleaf milkweed (Asclepias fascicularis): This drought-tolerant milkweed is native to the western US. It prefers full sun to partial shade and produces small round clumps of dusty pink flowers.
Find and Prepare a Suitable Container

If you winter sow milkweed outdoors, it helps to plant them in a cozy environment that traps moisture and heat. Fortunately, numerous household containers work well for this purpose.
Milk jugs are the most popular option, but you can also use plastic soda bottles or yogurt containers. As long as the container is clear plastic, can hold two inches of soil, and has a top that allows moisture to enter and escape, it will work just fine.
Once you have a suitable container, start by poking drainage holes in the bottom. These holes are essential for ensuring the soil doesn’t become water-logged. If you’re working with a narrow-top container like a milk jug or soda bottle, cut the container in half so you can easily fill it with soil and seeds.
If you don’t want to fuss with a DIY container, you can also use seedling trays topped with humidity domes. The trays will allow excess water to drain, and the domes will trap heat and moisture.
Fill the Containers with Soil Mix

Choose a well-draining soil mix that you would use for starting seeds. The mix should allow excess water to drain in order to prevent root rot and damping off. Therefore, you should avoid using native soil that’s heavy in clay.
Add two to three inches of soil to the bottom of each container. This mix will help keep them moist throughout the winter.
Sow the Milkweed Seeds

Once your containers are filled with soil, it’s time to add your milkweed seeds. Sprinkle a few on top of the soil, spacing each one about an inch apart. It’s okay if you sow extra—you can always thin crowded seedlings later.
Cover with a quarter inch of soil mix and then gently tamp. Water the soil until it’s moderately moist but not soaking wet.
If you cut your container in half, place the top half back on top, then tape the side to secure it. Place the lids on wide yogurt containers, then poke a few holes in the lids to allow water and light to enter.
Make sure you label your containers with the milkweed variety after planting. I also like to label my containers with the sowing date.
Place the Containers Outdoors

Your seeds are ready to go! All that’s left to do is place them outdoors and wait.
Choose a sunny location that receives natural rainfall. The sun will warm the soil, and rain and snow will help keep the soil mix moist.
Although these mini greenhouses are mostly hands-off, I like to check the containers at least once a week. The soil should feel moist but not wet, and the containers should remain upright. If you notice the wind is knocking them over, you can prop them up using bricks or other heavy objects.
Watch for Seedlings to Emerge

Although milkweed seeds may require cold to germinate, they won’t sprout until warm weather arrives. Depending on your climate and the variety, you can expect to see seedlings emerge sometime between March and May.
When you see the sprouts emerge, leave the container where it was. The top will continue to trap heat and moisture, allowing the milkweed to thrive. However, you can remove the top once the danger of frost has passed.
If the seedlings are closer than one inch apart, you should thin them. You can either pull or cut out unwanted plants or up-pot the seedlings to their own containers.
Transplant When the Weather Warms

Once your seedlings have three sets of true leaves, they’re ready to head to their final home. Although milkweed can tolerate frosts, I like to wait until the danger of frost has passed before planting. If you plant earlier in the season, you can use row covers to protect the plants from cold temperatures.
Make sure to keep the soil moderately moist as the plants settle into their new homes. They may grow slowly for the first few weeks, but their growth will jump once longer and warmer days arrive.