Last updated on October 21st, 2021 at 11:47 am
Growing Milkweed plants will attract many pollinators and butterflies to your yard, and in particular the beautiful and colourful Monarch butterfly. Growing milkweed is easy and can have many benefits for the garden. Learn how to grow milkweed plants, and bring beneficial insects and beautiful butterflies into your pollinator garden.
This year we planted milkweed from seed in late winter, and started our milkweed patch for the Monarchs. We didn’t expect flowers in the first year, however got a wonderful surprise.
In late August we had blooms on two plants, and by mid September we had milkweed pods. I was so excited, as this meant… well, more milkweed plants of course!
We have always grown lots of flowers for the pollinators at the farm. Growing a variety of different blooms has brought in so many beneficial insects.
We often had Tiger Swallowtail butterflies and caterpillars. They were attracted by the Ammi that we grew in the cut flower garden.
Occasional glimpses of Monarchs was a great reminder to plant milkweed to invite a larger number of these adorable butterflies. So we purchased some seeds, and got to growing them.
What Is Milkweed?
Milkweed is a native herbaceous perennial flowering plant.
Milkweed is the common name for a number of different species from the genus Asclepias. There are over two hundred different species of milkweed, and most of them are toxic to humans and animals.
The flowers of milkweed grow on tall stems and are very attractive and strongly scented. These blooms attract many insects to the plants.
Different species of milkweed will produce flowers, stems and leaves with subtle differences, and yet many similarities.
For example, Common milkweed grows from a single stem with broader leaves. However Swamp milkweed is multi branching with thinner leaves that are narrow and pointy. Yet the flowers on both species are similar, and both are hosts to the Monarch Butterfly.
Milkweed Sap Or Latex
If you tear a leaf of a milkweed plant, a sticky white sap will begin to ooze out. This substance is called milkweed latex, and resembles milk. This is one of the reasons that the plant got the name “milkweed”.
The sap is contained within the leaves and the stems of the milkweed plant.
The white sap is toxic and discourages animals and birds from grazing on or eating the milkweed plant. It can also be irritating if touched, so use caution when in contact. The sap can be an eye irritant, so be sure to wash your hands after touching a milkweed plant.
There are a number of insect species which have co-evolved with milkweed. They have adapted to be able to tolerate the toxins when ingested.
These species eat the leaves that contain the toxic alkaloids, and then carry the toxin from the milkweed within their bodies. This protects the insects from predators, who learn over time to avoid eating them for fear of getting sick.
Different species of milkweed may have different levels of toxicity. Some may cause mild illness, while others may be lethal if eaten.
Why Grow Milkweed?
Growing milkweed plants has become an effort by many gardeners to support and protect the Monarch butterfly population.
Milkweed is the only plant that Monarch butterflies eat.
Since Monarch populations are on the decline, gardeners can help to protect them by providing a food source in their gardens. Planting milkweed will help to feed both the larvae and the adults of the Monarch butterfly. Milkweed is the only plant that the larvae will eat in order to survive and grow.
Milkweed is the host plant for the Monarch butterfly.
The butterflies lay their eggs on the undersides of the leaves. When the eggs hatch the caterpillars feast on the leaves of the plant.
Milk weed flowers provide nourishing nectar for the adult monarchs, and essentially provides food throughout the whole Monarch life cycle.
Which Milkweed Is Best For The Monarchs?
Three of the best milkweeds to plant for the Monarchs include Common milkweed (Asclepias syriaca), Swamp milkweed (Asclepias incarnata), and Butterfly weed ( Asclepias tuberosa).
When considering planting milkweed, it’s important to plant a species that will grow well in your area. Any milkweed that is native to your growing location will be ideal.
We planted both Common milkweed and Swamp milkweed this summer, as apparently both can do well in our growing zone of 5b.
Both are fabulous host plants for the Monarchs, although Swamp milkweed is the species of choice.
Where Does Milkweed Grow Best?
There are many species of milkweed, and it’s important to grow a species that will grow and survive in your planting zone.
Know your planting zone, and consider growing native milkweed plants if possible. You will have the best success with plants that are adapted to your area.
Milkweed Growing Zone
It’s important to be aware of the growing zone in which milkweed will survive. Some species grow well in colder locations, and others in more tropical areas.
Swamp Milkweed is hardy from zones 3 to 8, and both Common milkweed and Butterfly weed are hardy from zones 4 to 9.
There are other species which are better adapted to the more tropical locations, such as Goose Plant Milkweed, Narrow Leaf milkweed and Tropical milkweed.
Does Milkweed Need Full Sun?
Milkweed loves the sun and will grow best if planted in a sunny location.
Our milkweed plants were planted in a garden that gets sun most of the day, and semi shade at the very end of the day as the sun dips in the sky.
The plants seemed to love this location and grew exceptionally well throughout the summer months.
Milkweed Soil Requirements
Milkweed will grow well in average garden soils and can grow in both sandy or clay soils.
Our milkweed was grown in clay soil, however we added compost to the garden bed and amended the soil before planting.
Does Milkweed Need A Lot Of Water?
Swamp Milkweed prefers to have moist feet as it’s name suggests, however this plant will tolerate some drought at times.
Moisture requirements are dependent on the type of milkweed planted. Butterfly weed prefers drier conditions.
We let nature take care of the waterings, and we were lucky not to have experienced a drought this summer. The plants grew well with the water from the natural elements of both the rain water and the early morning dew.
When Should I Plant Milkweed?
Since milkweed is a herbaceous perennial, the seeds do benefit from a stratification period to aide in germination.
Milkweed seeds can be planted in the garden in fall, and left to undergo natural stratification throughout the winter.
The seeds can also be planted indoors in late winter and grown under lights, and transplanted out into the garden in spring. We planted our milkweed seeds this way last winter and grew wonderful large seedlings in the garden this summer.
Alternatively they can also be winter sown, which we also had great success with last winter.
How Many Milkweed Plants Should I Plant?
For a good sized milkweed patch plant approximately twenty to thirty plants in a grouping.
Swamp Milkweed will form plants that are three feet in diameter when mature. It’s important to consider this size when determining your spacing and plant numbers.
Consider planting Swamp milkweed thirty to thirty-six inches apart.
You can plant them closer together, and then thin them out later if needed. Transplanting though may be difficult, as milkweed plants do not like to be disturbed once they are established.
Common milkweed and Butterfly weed can be planted eighteen inches apart. Common milkweed will spread by underground rhizomes and form groupings of plants.
Transplanting milkweed from the seedling tray to the garden is fairly easy. The plants will tolerate this handling without much stress as long as you take care when transplanting the root system.
Milkweed has a long taproot. As a result, it does not transplant well once it’s established in it’s garden location and has been growing there for a while.
It does not tolerate being dug up and relocated.
Keep this in mind when choosing the location for growing your milkweed plants. They should remain growing in the location where they have been planted if at all possible.
How To Grow And Care For Milkweed Plants
- Give the milkweed seedlings a good start by planting in a weed free bed.
- Water them in well, and keep them moist until they get established in the garden.
- Weed the bed as needed to allow lots of room to grow. During this first year of growth the roots are getting established and the plant is growing under the ground.
- Keep an eye on your plants as they grow, and watch for Monarch butterflies. They may still visit the seedlings even if there are not yet any flowers being produced.
- Milkweed plants do not really require much extra care after they have been planted.
- There is generally no need to stake or fertilize the plants.
- You can mulch to reduce weeds, however keep in mind that mulching will keep the soil moist, and some species of milkweed prefer a dry soil.
- Water as required depending on the milkweed species being grown.
- As your plants become mature they will start to bloom and produce seed pods. Milkweed will spread via seed dispersal.
- Harvest the pods if you want to prevent spread in your own garden, and share the seeds with others.
How Tall Does Milkweed Grow?
Milkweed can grow quite tall in ideal locations, many growing up to three to five feet in height. Goose Plant milkweed can grow up to six feet or higher in some locations.
Our first year Swamp milkweed plants grew two and a half feet by the end of the summer.
I was amazed to see the growth of the milkweed plants in only one season. They grew tall and sturdy, with lots of branching.
Does Milkweed Come Back Every Year?
Milkweed is a herbaceous perennial, meaning it will grow back every year from it’s established root system.
The plant goes dormant in winter months. In the spring new growth will appear and continue until seasons end.
What Can I Plant Next To Milkweed?
Cluster milkweed together with other perennials and shrubs for a nice display in the garden.
The milkweed flowers can continue to bloom for up to one month.
If you are lucky enough to have monarch caterpillars feeding on your milkweed, the plants can get a bit leggy (and that’s a good thing).
Therefore make sure to plant lots of pollinator friendly flowers and plants in the garden alongside the milkweed.
Our milkweed was planted close to our foxgloves and daylilies, and our garden was buzzing with pollinators.
Does Milkweed Spread?
Milkweed spreads by underground rhizomes in some species such as common milkweed, creating patches or colonies of the flowering plants. Common milkweed also spreads by seed dispersal.
Other species of milkweed are spread by seed production, such as swamp milkweed with it’s mesmerizing cottony coma. This is a fluffy structure with fine soft hairs that carries each seed off into the breeze.
When planting milkweed from seed, the plant is not expected to flower until the second or third year. We were blessed having a few flowers and seed production in the very first year.
Now we will be able to grow more plants and increase our milkweed patch even more so.
Have you tried growing milkweed plants in your garden? Be sure to leave a comment to share your experience!