How to Plant and Raise This Invaluable “Weed”

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Common milkweed is arguably not the prettiest plant. It is tall and gangly, with modest flowers and giant seed pods that dominate the plant in early autumn. Most of the people are not growing milkweed for its ornamental value. It’s okay, anyway, in the garden it is absolutely indispensable.

Milkweed is a humble plant whose role in the ecosystem is absolutely essential. Milkweed is the only plant that monarch caterpillars feed on. Without milk leaves, emperors cannot survive. Many other animals also depend on it.

Ready to get started? Let’s welcome some wild, wild plants to our gardens this year – starting with milkweed.

What is Milkweed?

Common Milkweed (asclepius syriaca) is a 2- to 4-foot-tall, perennial herb that grows wild in severe, rocky soils. Milkweed leaves are long and thick – rich in nutrients to support growing caterpillars. The flowers, which bloom in late spring through mid-summer, are small, purple, and fragrant. After flowering, milkweed produces giant pods filled with cotton seeds.

For centuries, milkweed — along with poppies, cornflowers and goldenrod — fed a plethora of pollinators growing between rows of corn and wheat in farm fields across the country. But when strong herbicides became common in the late 20th century, these field weeds faded from the landscape. The bees and butterflies they left behind also suffered, but none other than the beautiful monarchs.

In addition to monarchs, animals such as deer and rabbits eat milkweed. Dozens of species of butterflies and bees also feed on milkweed. It is an important plant for the ecosystem.

Fortunately, small-scale gardeners are introducing milkweed to the home garden. In the suburbs, small towns and the countryside, milkweed is making a comeback. But if you think you can just throw some seeds in the ground in the spring and summer with a healthy patch of milkweed, prepare for disappointment.

Milkweed can grow like a weed, but that doesn’t mean it grows easily without someone’s help.

varieties of milkweed

How to Plant and Raise This Invaluable "Weed"

If you are hoping to support a butterfly population in your area, choose milkweed that is related to your local ecosystem. While common milkweed fits well in most climates, it is not your only option.

swamp milkweed (Asclepius Avatar) grows well in the South, and Arizona milkweed (asclepius angustifolia) is a great choice for West and Southwest.

Like common milkweed, bog and Arizona milkweed are hardy plants that grow easily in their native climates. All three varieties are also safe and cherished for your local monarch caterpillar.

Growing milkweed is the same no matter what variety you are growing. I will focus on mango milkweed though. Since it is easily grown in zones 3-9, common milkweed is the most ubiquitous of the varieties.

planting milkweed from seed

Have you heard the horror stories of milkweed seeds that fail to germinate? Like many perennial herbs, asclepius syriaca To start from seed is supposed to be a challenge. Fortunately, once you have established your milkweed plants, they are easily spread through rhizomes.

The back of your seed packet may say “cold stratification.” If you’re planting in spring—or in zones 7-9—freezing your seeds means you should wrap them in cool, damp paper towels and stick them in the refrigerator. Refrigerate your seeds for about 6 weeks before planting.

But if you can choose your planting season—and you live in an area where winter temperatures drop below 40 degrees—choose autumn! Mother Nature does all the work by sowing milkweed seeds in late fall. Winter will chill your seeds better than in the refrigerator, so drop all the work and plant milkweed about a month or two before winter hits.

choose the right location

Milkweed does not require rich soil to grow well. Choose a sunny spot and loosen the soil. Milkweed is a full sun-loving plant. It grows best in loose, well-ploughed soil – which is why it grows so well in old-time corn fields.

Soil quality is not a concern. Milkweed grows happily just as well in clay, sandy soil or soft loam. but your soil should be Wet. Soak the ground before actually planting your milkweed seeds. The earth should look and feel saturated. Don’t worry about mulching or adding fertilizer, milkweed doesn’t even need to thrive.

Plant the milkweed seeds about an inch deep in the moistened soil. You can space the seeds about a half foot to 9 inches apart. If all the seeds have germinated, you will need to space the young plants about 18 inches apart. With proper cold stratification, milkweed seeds have a relatively high germination rate.

Be sure to mark the location of your milkweed seeds, especially if you are planting in the fall. It’s easy to forget where you put things in the winter. If you live in an area with a lot of snow – make sure the labels stick in the winter. We like to tie small scraps of cloth to the plant as a plant marker during winters as even sharps are not legible for 4-5 months under snow.


Milkweed seeds will germinate when the snow is gone and the ground will be warm and workable again. They will probably need some thinning in the spring, but give them a month or two of growth before taking them out.

Established milkweed plants spread by rhizomes, so a little extra space between seedlings guarantees more room for your plants to spread when they are ready. Most young milkweed plants will need about a foot of space between them to allow for healthy growth.

They can grow anywhere from 2 to 6 feet in height, so don’t crowd them. But if you are growing milkweed to support monarchs, try to keep your plants within easy crawling distance for hungry caterpillars. About 16-24 inches between young milkweed plants is ideal.

Milkweed Plant Care

Once your milkweed plants have successfully germinated and grown you can leave them in peace. Milkweed is a weed in the true sense – it likes to be neglected. Unless your garden is suffering from severe drought, don’t bother with milkweed.

In dry climates, milkweed appreciates occasional watering; Otherwise this hardy plant is ready to stand on its own roots.

pests and problems

While two- and four-legged predators are rarely a problem, aphids and slugs can sometimes wreak havoc on your milkweed plants. In moist, sultry heat, set up beer traps for slugs, or simply walk around the garden with a saltshaker to dispose of the tiny pests.

How to Plant and Raise This Invaluable "Weed"

If aphids are attacking your milkweed plants, you can kill them with insecticidal soap. Watch the monarch eggs carefully before spraying though, as insecticidal soap will kill your king with aphids!

Monarch eggs are white. There are rarely more than one egg per leaf, and butterflies lay them on the undersides of milkweed leaves. Milkweed aphids are yellow creatures, they live in clusters on both the top and bottom of the leaves. If there are any monarch eggs on the milkweed plant, wait. Do not treat the plant for aphids until all monarchs have gone away.

How to Plant and Raise This Invaluable "Weed"

harvest season

A hundred years ago, no one bothered to plant milkweed. It just grew in fields and along roads. But the world is now a little less welcoming of the wild, so milkweed needs help spreading. If you want to seed more milkweed plants, collect the seed pods instead of waiting for them to spread on their own.

Milkweed seed pods form in late summer or early fall. When the seeds are ripe and viable, the pods will burst – sending cotton seeds into the wind. Of course, if you’re trying to collect seeds, this scatter is less than helpful.

How to Plant and Raise This Invaluable "Weed"

However, harvesting the pods early is not an option, as the seeds are never viable in raw pods. So, what should the gardener do?

rubber band

I’ve found that gently securing a rubber band around newly made pods is a great way to keep the seeds in during ripening.

Many of my friends and family are creating butterfly sanctuaries in their gardens, and they all want milkweed seeds. When pods form on our huge bed of milkweed plants, I rubber band some of the pods for gift giving. Once the pods are secured, all you have to do is wait. After a while, the pods will begin to split along the edges. When it splits, your pod is ready to harvest.

The rubber band holds it together until you get it in and out of air. I like to put the pods in a paper bag, remove the rubber bands, and then shake off the seeds. That way everything stays together, and you avoid making a fuzzy mess in the house.

Remember to allow at least some of the seed pods to scatter freely. We want to make sure there are still wild milkweed plants as well as deliberate plants.

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