Planting milkweed seeds is a great way to get a lot of milkweed plants for your garden. Milkweed isn’t difficult to grow from seed and the plants are beautiful, long blooming, and support many species of pollinators, including monarch butterflies. In this article you’ll learn four easy techniques for planting milkweed seeds and get tips on caring for the seedlings. 

Why grow milkweed? 

Gardeners know the value of growing milkweed in their gardens. These are beautiful perennial plants that add bold color to the summer garden, but as the sole larval food source for monarch caterpillars they’re also a host plant. The adult butterflies lay eggs on milkweed plants and when the caterpillars hatch they begin to feed on the leaves. If you wish to create a monarch butterfly habitat, often called a monarch waystation, it’s essential to plant milkweed in your garden. 

Want to learn more about planting milkweed seeds? Watch this video:

Types of milkweed

There is a wide variety of milkweed species you can grow in your garden. It’s best to select those that are native to your region or will thrive with the growing conditions of your yard. Here are five types of milkweed popular with gardeners:

• Common milkweed (Asclepias syriaca) – Native to many parts of North American, common milkweed is a hardy perennial with large rounded pink flowers. It’s an important pollinator and butterfly plant, but be warned, it is aggressive and spreads by rhizomes, underground roots. 
• Butterflyweed (Asclepias tuberosa) – The bright orange, flat-topped blooms of butterflyweed are beloved by gardeners and pollinators. It forms large clumps in the beds and borders with the plants growing about 2 feet tall and 3 feet wide. 
• Swamp milkweed (Asclepias incarnata) – Although the name implies this is a milkweed for swamps and wet yards, this is easily grown in average garden soil. This is my go-to species of milkweed because it’s native to my northeastern region. The plants grow 4 feet tall and form 3 foot wide clumps of foliage and flowers.
• Purple milkweed (Asclepias purpurascens) – This species has pretty purple star-shaped flowers held in rounded clusters. The plants grow 2 to 3 feet tall and bloom from late spring through early summer. It spreads by rhizomes, but isn’t overly aggressive. 
• Showy milkweed (Asclepias speciosa) – Showy milkweed looks similar to common milkweed but doesn’t wander all around. The plants grow 4 to 5 feet tall and are topped with pink flower clusters in mid-summer. 

Where to buy milkweed seeds

When it comes to sourcing milkweed seeds there are couple of options. First, if you already have milkweed plants in your garden you can collect mature milkweed pods from late summer through mid-autumn. As the pods turn from green to brown, they’ll split open to expose the seeds. At this point I gather each milkweed pod by clipping it from the plant and placing it in a paper bag. Once I’ve collected all the pods, I separate the seeds from the milkweed fluff by opening each pod, grabbing the center stalk at the top end, and carefully sliding my hand down to collect the seeds. I’ll then spread the seeds on newspaper to fully dry, eventually storing them in labelled envelopes.

If you don’t have any milkweed plants or a friend who can share a few pods, order milkweed seeds from seed catalogs. Or find seed packets at your local garden centres.

Planting milkweed seeds: 4 easy techniques

As noted above, there are four techniques for planting milkweed seeds.

1. Direct seeding in autumn
2. Direct seeding in spring
3. Starting seeds indoors in spring
4. Winter sowing

Each of these has its own drawbacks and benefits. Let’s look a little closer at these four methods. 

1) Planting milkweed seeds: Direct seeding in autumn

This is the easiest method for planting milkweed seeds and it mimics the natural propagation process. In nature milkweed seeds are scattered late in the season when the seed pods split open, the seeds catch the wind, and then fly away on their fluffs. The seeds land and go through the freeze and thaw cycle of winter which naturally stratifies the seed to prompt germination. 

If you wish to use this technique for planting milkweed seeds begin by collecting them in late summer or autumn from the mature dried pods of existing plants or buy seed packets for your desired milkweed species. Direct sow the seeds after the first frost in autumn and up until the ground freezes by sprinkling them across the prepared soil surface. I space them about an inch apart and cover them with a scant one-quarter inch of soil. Water the planting site well.

The following spring thin the young plants as they sprout, moving the thinned seedlings to a new spot. Most milkweed plants should be spaced 12 to 18 inches apart, depending on the species. 

Benefits: This method of planting milkweed seeds is very easy, but it’s also cost effective because you don’t need seed starting supplies like pots, cell packs, and trays. 

Drawbacks: The seeds may wash away in heavy autumn or winter rains resulting in fewer seedlings the following year. You’ll also need to thin the small plants in spring so they have space to grow well and produce a strong taproot. 

2) Planting milkweed seeds: Direct seeding in spring

Planting milkweed seeds outdoors in garden beds in spring isn’t as reliable as planting in fall. This is because the seeds don’t undergo a chilling period, called cold stratification, to soften their seed coats and encourage germination. That said there is an easy and effective way to improve sprouting – stratify the seeds in your refrigerator in late winter. They’ll need at least 30 days of cold temperatures so plan on leaving the seeds in the fridge for 4 to 6 weeks. 

As for stratifying instructions, I use a small plastic container or ziptop baggie and add about a half cup of moistened potting mix. You can also use damp sand or even roll the seeds up in moist paper towels. I add a tablespoon of milkweed seeds to the potting mix, seal the baggie, and using my fingers, mix the seeds into the soil. Label and place the baggie in the fridge for at least 4 weeks and up to 3 months. Once the seeds are stratified you can plant the milkweed seeds outdoors in your spring garden. 

Benefits: If you didn’t get a chance to sow milkweed seeds the previous autumn, this technique provides a simple ‘cheat’ to help boost germination rates.

Drawbacks: If planting milkweed seeds in autumn you don’t need to go through the extra step of stratifying the seeds in the refrigerator. This method uses an extra step and takes more time. 

3) Planting milkweed seeds: Starting seeds indoors in spring

I start a wide variety of flower, vegetable, and herb seeds indoors each spring. However, I rarely start milkweed seeds this way as this method takes more time, supplies, and fussing. As with planting milkweed seeds outdoors in spring the seeds need a cold treatment before you can sow them inside. Follow the stratification instructions above giving the seeds at least 4 weeks in the refrigerator. 

Once the seeds are ready to plant, fill 1020 seeding trays with damp seed-starting potting mix or all-purpose potting mix. Next, open the zip top baggie and grab a handful of the soil-seed mixture. Sprinkle it evenly overtop the seed-starting mix and lightly tamp it down to ensure good soil-seed contact. Water and cover the tray with a plastic humidity dome or a sheet of plastic wrap. After the seeds sprout, in 7 to 14 days, move them to a sunny window or under a grow light.

Benefits: Starting the seeds indoors allows you to control the growing conditions to help boost germination rates.

Drawbacks: Not only do you need to take the time and effort to stratify the seeds but you also need to buy seed-starting equipment like trays, potting mix, and grow lights. 

4) Planting milkweed seeds: Winter sowing

Winter sowing is my go-to method for planting milkweed seeds. It’s quick, allows the winter weather to stratify the seeds, and results in dozens, if not hundreds of seedlings. I start to winter sow seeds starting in December and have even winter sown seeds in February with good results.

Seeds are planted in milk jugs, salad containers, or soda bottles filled with a couple of inches of potting mix. The containers are taped shut and placed outdoors where the cold temperatures and moisture of winter break seed dormancy. By spring the small seedlings can be moved to garden beds. To learn all about winter sowing and the best plants for this technique check out our winter sowing guide.

Benefits: Winter sowing is an effective way to start a lot of seeds and uses recycled items like milk jugs and soda bottles. 

Drawbacks: Gathering and prepping the winter sowing supplies takes time and you’ll need to buy potting mix. 

Best location for planting milkweed seeds and seedlings

Most species of milkweed thrive when grown in a site with full sunlight and average, well-drained soil. Some, like swamp milkweed, can take part shade and increased soil moisture. However, it’s essential to select a type suited to the conditions of your garden. When planting milkweed, think like a butterfly. Monarchs only lay their eggs when there is enough milkweed to support the growing caterpillars. Therefore plant in large clumps of at least 5 plants to ensure an adequate food supply. The more milkweed you plant, the more monarchs you’ll welcome to your garden. 

Caring for milkweed seedlings

I find milkweed to be a ‘hands off’ perennial that is drought tolerant, insect and pest resistant, and long flowering. Help the young seedlings settle into your garden beds by watering weekly if there has been no rain. Stay on top of weeds the first year to eliminate competition and help the plants grow well. Native plants, like milkweed, don’t have high fertility needs, but I do apply a granular organic flower fertilizer around the plants each spring. This encourages robust growth and lots of flowers.

Milkweed plants make excellent garden perennials in mixed beds and borders, as well as in wildflower meadows. Keep in mind that it’s likely your young seedlings won’t flower the first year. Most types of milkweed flower the second year from planting so be patient. 

For more information on milkweed and other pollinator plants, be sure to read these expert articles:

• How to collect and harvest milkweed pods
• Milkweed 101
• Create a habitat garde for wildlife
• Butterfly host plants