When and How to Sow Milkweed Seeds For an Abundant Butterfly Garden

Milkweed flowers grace natural landscapes throughout North America. They form big, bright clusters with dozens of small blossoms. Nectar and pollen flow freely from the flowers, offering bees, butterflies, and pollinating flies an opportunity to feast!

Because these plants are native to North America, they sprout during distinct times of the year throughout our changing seasons. You’ll want to mimic this species’ natural conditions to help it thrive within your garden.

These plants are slightly different from common garden ornamentals like zinnias and sunflowers. They’re perennial in most zones, and their seeds need cold stratification to germinate. With the right care and treatment, you’ll turn a dozen milkweed seeds into stately plants with stunning blooms!

When to Sow Milkweed Seeds

When to sow seeds depends on the variety, your local climate, and whether or not your seeds undergo cold stratification. We’ll review each factor to determine when you should sow these native plants.

Choose Your Variety

There isn’t one milkweed. Rather, there are dozens of varieties that grow in a range of habitats. They’re all equally important in helping butterflies. Different butterflies prefer different milkweeds, so the best types for your garden are the ones that are local to the surrounding landscapes. 

West Coast gardeners can choose from showy or narrowleaf milkweed, while East Coast growers should grow common or swamp milkweed, or butterfly flower. Central U.S. gardeners should opt for swamp, showy, or common milkweed, or butterfly flower. 

Another consideration is the specific habitat. Certain species like moist, swamp-like conditions, while others thrive in dry, sunny, and warm locales. Take stock of your garden and see which it resembles. Is it moist, shady, and cool, or is it hot, arid, and sunny? 

Swamp milkweed is the best kind for moist gardens, while narrowleaf milkweed and butterfly flower are incredibly drought-tolerant. Dozens of rarer milkweed varieties exist that fit more specific conditions. The lesser-known species may require more care to thrive. However, they often offer unique colors, shapes, and scents that the common types don’t.

The Best Seasons for Sowing

Fall is the best season for sowing this native wildflower. Most varieties require cold stratification, meaning they need cold temperatures for weeks before germinating successfully. By sowing seeds outdoors before frost arrives in fall, you allow them to naturally undergo cold stratification.

Although fall is the best time for planting, it’s also possible in winter and spring. These two seasons have adverse effects on the seedlings, so we’ll use a few special methods to ensure they sprout no matter when you start them. 

Summer is the only season to avoid sowing milkweed seeds. It’s too hot and dry for tender seedlings, and the young plants will struggle to establish themselves. 

Some seeds come pre-stratified, meaning you don’t have to give them a cold period! Look to the labeling or instructions on the seed packet you purchased to see if they’re stratified. If the packet doesn’t say anything about cold stratification, chances are your seeds will need to undergo a proper chill period before they germinate. 

How to Sow Milkweed Seeds

How you sow this wildflower depends on the season you’re sowing it. Fall, winter, and spring sowings all require slightly different techniques to ensure seeds sprout without issues. 

Fall Sowing

Sowing seeds in autumn is the easiest and simplest way to grow milkweed. They stay dormant in fall and winter as they undergo cold stratification. As temperatures warm and days lengthen in spring, they germinate into seedlings. Fall-sown plants tend to bloom their first year because they have ample time to establish themselves.

Autumn occurs between August and November in North America. For planting, you want the soil to be cool but not freezing so the seeds stay dormant. August may be too early in most regions; you can wait to plant the seeds until around a month before your first average frost date if you choose. 

Before sowing in the fall, first prepare the planting site. Clear any weeds and debris, and rake the soil so it has an even surface. Sow no more than a quarter inch deep, covering them with a thin layer of soil. Water the site well; you want the soil to be moist, not soggy, throughout the cool seasons.

In extremely cold climates, it’s best to cover the seeds with a thin layer of mulch like compost, fall leaves, or leaf mold. The mulch insulates them, and you can remove it in spring to let the seedlings grow tall and strong. 

Winter Sowing

For winter sowing, you’ll use pots with clear humidity domes to protect the plants while conditions are harsh in the landscape. This exposes your milkweed seeds to cold, without the full exposure they would receive if you sowed them directly in the garden.

Start by preparing small pots with potting soil. Use cell trays for growing dozens of seedlings, or use small separate pots if you’re only sprouting a few. Plant a quarter inch deep in the soil, then water the pots so the dirt is moist and not soggy.

After watering, place a humidity dome on top of the pots. This traps humidity and heat, keeping your seeds safe. Open the vent on the domes if they have one, or poke a few holes in their tops to allow airflow throughout the containers. 

Place these protected containers in a shady location—under an awning, porch, or patio is perfect. Ensure the pots stay moist, and uncover them as they sprout and flourish in spring. 

Spring Sowing

Did you miss fall and winter plantings? Fear not, as spring sowings are easy and simple to facilitate. You’ll want to mimic winter’s cold for your seeds. This will trick them into sprouting in spring, as they believe they’ve been outdoors for the winter.

You can give your milkweed seeds cold stratification with your refrigerator. Its temperatures are ideal, mimicking winter cold without harsh frost. Place the seeds in pots with moist soil and cover them in bags in the fridge. An alternative option is to layer the seeds between moist paper towels in a container. Store either in the fridge for three weeks to three months before planting. 

Bring the seeds out of the fridge after the chill period, and place them indoors near a bright windowsill. If they’re in moist paper towels, take them out and plant them in pots before moving them to a bright location. Transplant seedlings outdoors under full sun or partial shade when they have at least four adult leaves and frosts are no longer occurring. 

Popular Varieties

So, which type of milkweed is best for you? These six types are the most common and the easiest to start in a wide range of garden conditions. Choose species endemic to your local area, meaning they grow near you already in wild spaces. Endemic species help your local butterflies the most!

Common

The common species is anything but average! It grows wild throughout the central and eastern U.S. states, filling prairies, meadows, and wild spaces with bright pink-white blooms. The flowers sprout in globular clusters that create perfect landing pads for hungry bees, butterflies, and caterpillars. 

Common milkweed is native to Kansas, the Dakotas, and Nebraska, east from Maine through the Carolinas. It’s hardy from USDA hardiness zones 3 through 9, sprouting perennially from underground rhizomes. 

Butterfly Flower

This exceptional cultivar grows throughout much of common species’ range, except butterfly flower also thrives in dry and hot southern states like Texas, New Mexico, and Georgia. It’s the perfect species for warm gardens in need of flowers for pollinators.

Rather than pink, white, or lavender flowers, butterfly flowers bloom bright orange blossom clusters that shine under the summer sunshine. Plant them amongst common milkweed for a stunning contrast between the two. 

Swamp

Gardeners with wet landscapes rejoice! Swamp milkweeds are perfect for your moist, ornamental garden. Grow a mix like ‘Irresistible Blend’ for pink and white blooms on separate plants. Their blossoms emit a vanilla fragrance that attracts butterflies by the dozens.

Although swamp milkweed prefers wet soil, it also survives short droughts in summer! Ensure the site stays moist throughout the year for the biggest, most fragrant flowers. 

Narrowleaf

Narrowleaf milkweed has one of the smallest native ranges of all U.S. wildflower species. It grows wild throughout warm, moist regions in the Pacific Northwest, California, Nevada, Idaho, and Mexico. It’s drought tolerant like butterfly weed, though it prefers moist conditions during the growing season.

This species sports lovely pink-white flower clusters that sprout atop thin, needle-like leaves. It’s perennial, growing well in zones 6 through 10. 

Showy

Showy milkweed excels on the West Coast like the narrowleaf species. It has a larger native range, growing wild from the Great Plains westward through California, Oregon, and Washington. It sprouts similarly to the common type, although its bloom clusters are larger and more showy. Star-like flowers erupt in globular clusters with pink, white, and fuschia colors.

If you want to help Monarch butterflies, this showy species is an ideal type to plant. Grow it in full sun with regular water, and it’ll return year after year.

Tweedia

The last species on this list isn’t native to North America, though it is to South America! It isn’t a host plant for our native butterflies, though it does offer nectar and pollen to hungry pollinators. With blue flowers, soft green leaves, and a semi-vining nature, tweedia is ideal for growing on trellises or stakes.

Frequently Asked Questions