Growing Milkweed from Seed Easily!

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grow milkweeds from seeds

Butterflies, hummingbirds, and bees love this perennial. It’s ridiculously easy to grow, needs zero maintenance, does well in crappy wet soil (clay-like) and provides verticality (height) in your garden.

Also, Monarch caterpillars utilize the milkweed as their exclusive food source while in the larval stage. Monarchs not only like but require Milkweeds! Mature milkweeds bloom in the summer months, usually beginning in June. Because of this, milkweeds are sometimes referred to as Butterfly Milkweeds.

I’ve become a huge Milkweed grower and supporter. I’ve found growing milkweed from seed is a joy, and should be in every thoughtful gardener’s garden.

swamp milkweed plants in the garden

A bee visiting one of my swamp milkweeds in the middle of summer.

Photo by author.

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Milkweed (Asclepias) is a very hardy, attractive, beneficial perennial plant. Milkweed will grow back every year. It is a native plant that prefers moist environments, they do well in poor-draining soils.

Milkweed will turn brown or black during the winter, and will appear like it is dead forever. But in the Spring, new growth will come up out of the ground where it was planted!

It is a herbaceous perennial, meaning it has no permanent woody growth or base above ground. Its continued growth is possible because of its rhizome, its mass of underground roots. In general, rhizomes have short internodes, send out roots from the bottom of the nodes, and generate new upward-growing shoots from the top of the nodes. (Wikipedia)

Milkweeds do contain a certain amount of toxicity. Some Native peoples of America have used milkweed extract on their arrows to fight and hunt more effectively.

grow swamp milkweed for pollinators
The buds that drive pollinators crazy! Image by frederick, flickr

Many perennial plants live this way: their warm season green growth dies off when the weather turns colder, but the plant underground is still very much alive. Many plants need their leaves and foliage intact for as long as possible, so that photosynthesis can occur, further providing nutrients to the rhizome or tuber below ground.

Growing Milkweed from Seed

You can purchase an established Swamp Milkweed plant from a nursery or store. However, I think the best way to grow it is growing milkweed from seed. Milkweed seeds are available from retail locations.

Also, you can scout out milkweeds in semi-public places and take a seed pod home when the plant develops them. Their seed pods become visible in the late Summer or Fall (see above image.) Their seed pods are ripe for picking when you see some white fluff (technically, “pappus”) bursting out from their pods.

I sell my own hand-harvested swamp milkweed seeds in my webstore!

Growing Milkweed from Seed

Nothing could be easier than collecting seeds from a milkweed in the Fall. Their seed pods are quite fun: their seeds are surrounded by tufts of cotton-like fibers (“pappus”) that allow them to spread via the wind like Dandelion seeds. There is an enormous amount of seeds in just one pod, and a milkweed plant will develop a dozen pods or more at the end of its growing season. Harvesting seeds from a milkweed seedpod is very easy. It is quite obvious when its pods are ready to be harvested.

growing milkweed from seed one pod contains about 100 seeds
Milkweed seeds ready to harvest, note the preponderance of fluff” (pappus) surrounding seeds. Image, H. Zell, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

When I’ve harvested swamp milkweed seeds, I usually just snipped a whole seed pod and place it in a manilla envelope. Trying to separate the fluff from the seed is a tedious and unnecessary step, so don’t spend time doing it.

The seeds themselves have a tear-drop shape. They’re about 1/8″ long, about half that in width.

I was quite surprised to see how strongly the milkweed seeds grew, despite not having any experience doing it before. I kept the seed pod in its envelope in a cool environment, our garage. The temperature of the garage through the fall and winter ranged between 48F and 57F degrees. This temperature range seems to be just fine for seed storage.

How to Plant Milkweed Seeds

UPDATE: I had terrific luck and success growing milkweeds from seeds my first year. My second year, not as much. What did I do different?

Cold stratification.

Milkweed seeds need to experience a cold winter season before they’ll germinate. The procedure I follow now to grow most seeds (starting seeds in heat-mat, grow lights) does NOT do any good for milkweeds (nor forShasta Daisies, Coneflower, or Rudbeckias.) I sowed milkweed seeds into 22 homemade newsprint “cups.” They sat in their environmentally controlled greenhouse for a month. No sprouting. I took this flat of seeds and put it into the refrigerator for over a month, and then I put the flat to an outdoor (unheated) greenhouse. NOW the milkweed seeds are germinating quite well, all 22 cups are sprouting.

how to plant milkweed seeds
One tray of swamp milkweed seedling starts, right side of shelf of my outdoor mini greenhouse. I prefer ready-made seed cups like these. Image by author.

In mid-Winter, I prepare my seedling cups for sowing. You can use biodegradable paper seed starter cups which work terrifically, and they’re not expensive.

You can also use fiber egg cartons that you save. Note: Egg cartons don’t seem to work quite as well as premade starter cups: it’s difficult to tear the individual cups apart for transplanting the growing seedlings, and it’s difficult to open up the bottom of the carton cups to allow root spreading after transplanting. Also, egg carton cups seem to generate (benign?) green mildew after a few weeks.

use fiber egg cartons as seedling cups
Egg cartons prepared for seedling soil. Image by author.

Also, select a good seedling start soil.

seedling potting soil

I’ve used Miracle-Gro’s Seed Starting Potting Mix with excellent results. You want to choose a seed starting potting mix formulated for fast root development, and is appropriate for your baby greens. Amazon sells a lot of great suitable potting mixes for your seedling starts.

Milkweed seeds germinate within a few weeks after being sown. I’ve found it’s best to only plant three seeds per planting cup. Put the seeds down to a modest depth of 1/4″ inch or less. My harvested swamp milkweed seeds have grown very strongly when housed in a (mini, portable, inexpensive) greenhouse.

Every single seed sown has developed. I cannot say that for other harvested seeds. Milkweed seeds just seem to take off and continue growing from seed easily. They even tolerated a few dry periods, overwatering, temperatures just above frost, and heat.

Mini greenhouses retain (magnify) ambient sun heat. If it’s 55F degrees outside on a sunny day, I’ve recorded temperatures as high as 92F inside a closed mini greenhouse. Greenhouses are also terrific at retaining humidity, something milkweed seeds thrive in.

Milkweed Plant Care

Milkweeds are very easy to grow. They tolerate conditions that a lot of other perennials would not. Swamp milkweed care requires very little from its gardeners, but a few standout points do remain:

established 4 year old swamp milkweed growing in warm Spring sunshine
My first purchased swamp milkweed in mid-May, about 2 1/2 feet tall, in its fourth season in my garden. Image by author.

Does milkweed need full sun? Yes, Milkweeds prefer full sun exposure.

When does milkweed bloom? They bloom in the Summer months, June through August.

Does milkweed grow back? Yes, as a perennial plant, they grow back every year. As long as the plant’s rhizome remains healthy underground, it will return year after year.

While fertilizing your milkweed isn’t necessary, applying some general (5-5-5) fertilizer will definitely help keep it healthy. Since swamp milkweeds prefer moisture, they should be watered in rain-free, dry periods.

This, from the University of Texas Plant Database who state that growing milkweed from seed is “easy to start:”

Asclepias incarnata

Water Use: High
Light Requirement: Sun , Part Shade
Soil Moisture: Moist , Wet
CaCO3 Tolerance: Medium
Soil Description: Rich, wet, very muddy to average garden moisture. One of the few ornamentals that thrives in mucky clay soils. Prefers neutral to slightly acidic soil but will tolerate heavy clay.
Conditions Comments: With its showy flower clusters that attract butterflies and hummingbirds, swamp milkweed is underutilized in gardens. In moist soils or in a pond, it will thrive. The interesting seed pods look like other milkweeds. Swamp milkweed will inevitably have aphids. The insects are not a problem unless the plant looks sick; at that point an effective treatment is to spray the plant and aphids with soapy water.

Another possible treatment is to support the plant part with your hand and blast it with high-pressure water. Good for wetland gardens and habitat.

Starting Milkweed Seeds

I’ve had terrific success planting milkweed seeds in late Winter. I start them in seedling cups and nurture them in a mini greenhouse. This keeps them out of the cold most of the time, they are in a humid environment, and are protected from pests. Growing milkweed from seed in a greenhouse of any size or construction is a great way to raise them, as you can water them simultaneously.

I have attempted to sow milkweed seeds directly into the garden. Unfortunately, the young green leaves of milkweed seedlings are delicious to pests like slugs. If you do elect to sow directly into earth, protect against pests. You can surround the seedling sites with crushed eggshells or commercially prepared slug and snail repellant.

Shop My Personal Seed Store!

Visit My Webstore Now!

buy hand harvested seeds from home gardener grower

My seed shop is now open! Currently available are

  • Tall Shasta Daisies
  • Dianthus (“Sweet William”)
  • Hollyhocks
  • Gaillardia “Blanket Flower”
  • Swamp Milkweed

I’ve grown most of these beauties for a few seasons now, and hand harvest their seeds.

I’ll add more plants and flowers as I grow them successfully. Coming: Rucbeckia, Anise Hyssop, Columbine, Dusty Miller, Lupines…

Can You Grow Milkweed in a Pot?

It is advisable to start milkweed seeds in containers. I have found slugs are attracted to the young milkweed leaves, they find them delicious to eat. It is a good idea to start your milkweed seeds in starter pots, like biodegradable fiber pots or even empty fiber egg cartons.

They are quite hardy when you allow them to grow this way.

The picture below shows a grouping of my swamp milkweed seedling starts, happily growing in their new home: an oak barrel container. They are the tallest, planted in the center. There are three individual seedling starts, and there are three clumps, for nine seedling starts in total in the picture. Planted with them are Mexican sunflower (left) and Hollyhocks (right) which are also seedling starts. All three of these seedlings were started at about the same time, about 10 weeks before this picture was taken.

milkweed seedlings transplanted to container
My harvested swamp milkweed seeds about 9 weeks old, 12″ high.
Image by author.

You can plant and keep milkweed in a single container. Keep in mind that they grow to about four feet in height. Your goal when selecting a suitable pot for your milkweed is to get one tall and large enough so it won’t blow over. You’ll want to choose a container that’s at least 18″ high.

Milkweed Planting Companions

Since milkweeds grow vertically, and aren’t bushy, there are many plants that you can plant in this container to complement your milkweed. Milkweeds do prefer to be watered regularly, so plant alongside similar plants and flowers. I have a lovely Canna Lily near my largest Milkweed.

Go for a medium height flower of contrasting color, ideally one that attracts pollinators as well. Plant a few clumps of Shasta Daisies in front of your milkweeds for a stunning vignette! Rudbeckias (“Black Eyed Susan”), lobelias and cone flowers (“Echinacea“) would look terrific as well as providing pollinators additional targets to go along with your milkweeds.

Because of their planting habitat, benefit to pollinators and winged friends, and their ease of care, I’ll continue growing milkweed from seed for the rest of my life!

Photo of author

Author

After years of denying it, Donald finally admits one passion in life is gardening. More specifically: growing seeds, plants, flowers and edibles and helping them to be the best possible. Neighbors call him a Green Thumb. He lives in Western Washington with his wife of 24+ years and three cats.

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