When to cut back tropical milkweed?

Contents

Winterizing Milkweed: Caring For Milkweed Plants In Winter

Because of my favorite hobby of raising and releasing monarch butterflies, no plant is as close to my heart as milkweed. Not only is milkweed a necessary food source for adorable monarch caterpillars, it is also a beautiful garden plant that attracts many other pollinators, while not requiring much maintenance. Many wild milkweed plants, often considered weeds, will grow happily wherever they sprout without any “help” from gardeners. Though many milkweed plants need only the help of Mother Nature, this article will cover winter care of milkweed.

Overwintering Milkweed Plants

With over 140 different types of milkweed, there are milkweeds that grow well in almost every hardiness zone. Winter care of milkweed depends on your zone and which milkweed you have. Milkweeds are herbaceous perennials that flower throughout the summer, set seed and then naturally die back in fall, going dormant to sprout anew in spring. In summer, spent milkweed flowers can be deadheaded to prolong the blooming period. However, when you are deadheading or pruning milkweed, always keep a careful eye out for caterpillars, which munch on the plants throughout the summer.

In general, very little milkweed winter care is needed. That said, certain garden varieties of milkweed, such as butterfly weed (Asclepias tuberosa), will benefit from extra mulching through winter in cold climates. In fact, no milkweed plant will object if you want to give its crown and root zone some extra winter protection.

Pruning can be done in fall but isn’t really a necessary part of winterizing milkweed plants. Whether you cut back your plants in fall or spring is totally up to you. Milkweed plants in winter are valued by birds and small animals who use their natural fibers and seed fluff in their nests. For this reason, I prefer to cut milkweed back in spring. Simply cut last year’s stems back to the ground with clean, sharp pruners.

Another reason that I prefer to cut milkweed back in spring is so that any seed pods that formed late in the season have time to mature and disperse. Milkweed plants are the only plant that monarch caterpillars eat. Sadly, because of man’s heavy use of herbicides, there is a shortage of safe habitats for milkweed and, therefore, a shortage of food for monarch caterpillars.

I have grown many milkweed plants from seed, like common milkweed (Asclepias syriaca) and swamp milkweed (Asclepias incarnata), both of which are favorites of monarch caterpillars. What I have also learned from experience is that these milkweed seeds need a cold period, or stratification to germinate. I have collected milkweed seeds in autumn, stored them through winter, then planted them in spring, only to have just a small fraction of them actually germinate.

Meanwhile, Mother Nature disperses milkweed seeds all over my garden in autumn. They lay dormant in garden debris and snow through winter, and germinate perfectly in spring with milkweed plants everywhere by midsummer. Now I let nature take her course.

Tropical Milkweed Seeds and Plants (Asclepias curassavica)

Tropical Milkweed for Monarchs and More

Tropical Milkweed
(Asclepias curassavica)

Asclepias curassavica milkweed has several common names including Tropical Milkweed, Bloodflower, Scarlett Milkweed, and Mexican butterfly weed. There are many other types of milkweed but this milkweed is one of the Monarchs favorite host plants.

Care of Asclepias Curassavica

Tropical milkweed is a perennial only in zones 8-11. It is originally from South America but has naturalized in our tropical zones. Elsewhere in the US and Canada it is grown as an annual because it is a fast grower and flowers all summer and into the fall.

A Swallowtail Butterfly
nectars from Bloodflower

Asclepias curassavica prefers full sun but can handle a little shade. They can grow from 2-4 feet tall depending on conditions. You will get the best performance from Bloodflower if planted in full sun and moist well-drained soil. However, it can also tolerate some dryness once established.

Tropical milkweed can also be planted in containers and even kept indoors over winter if you have a bright sunny place for it. It will remain evergreen all winter indoors. In zones 9b-11 it will remain evergreen outdoors. It will die back to return in the spring in zones 8-9.

If you live in zones 9b-11 where it stays green all winter it is recommended by most Monarch researchers to cut it back in the winter so new growth will form or to not plant it at all in these areas. The reason is that Monarchs can get a parasite called OE and this parasite can survive on the leaves of any milkweed. So, if a milkweed does not die back and get new growth then the OE may stay present and continue to re-infect other Monarchs from year to year.

This is not an issue in areas where Tropical milkweed (or any other milkweed for that matter) does not stay green all winter.

Tropical Milkweed Plants for Butterflies

Asclepias curassavica is a Host Plant for two butterflies, the Monarch butterfly and the Queen butterfly. The Monarch butterfly can be found all around the US and into Canada. The Queen butterfly is found in Florida, our southwestern states, and down into Mexico.

A Queen Butterfly

Not only will Asclepias curassavica attract egg-laying Monarchs, it is also extremely attractive to all kinds of butterflies as a nectar plant. That is part of what makes milkweed such a great plant in the garden. In my garden it is especially attractive to the larger varieties of butterflies such as the Swallowtails.

When using Tropical milkweed to raise Monarchs indoors, you can simply break some leaves off and put them in a container with the caterpillar. The leaves will stay good for about 24 hours without water. We usually raise our Monarchs in large clear plastic containers. I just change out the old leaves and the frass (caterpillar poop) everyday and replace with fresh leaves.

You can also keep the leaves good for several days by putting them in a baggy in the refrigerator. This way you can give your friend, neighbor, school, etc, a caterpillar and some food without having to bring them fresh food each day.

Monarch Caterpillars Eating Tropical Milkweed

Starting Asclepias curassavica from Seed, Propagation

Tropical milkweed flowers prolifically so there is plenty of seed to collect for the following spring and share with friends. Milkweed flowers produce pods that open up revealing seeds attached to white fluff that blows around in the wind. If you remove the pods once they have dried and just started opening then you can strip the seeds off pretty easily.

Asclepias curassavica seeds do not need to be cold stratified (since it is a tropical plant). You can start these indoors about 4-8 weeks before the last frost. Plant the seeds about 1/4 inch deep and keep moist. They will germinate in about 2-3 weeks. They can go outside after the danger of frost has past. Plant them about 18-24 inches apart. I usually plant mine about 18 inches apart. You can pinch these back to make a fuller plant.

Pearl Crescent Butterfly nectaring on Asclepias curassavica

Tropical milkweed can also be direct sowed in the spring. In the South you can sow the seeds in the fall if you wish. They like warm soil so germination could be slow or erratic until the soil warms up.

This milkweed can also be grown from cuttings. I do not personally have experience with this but it is a common way of propagating Asclepias curassavica.

Tropical Milkweed Seeds and Plants

Asclepias curassavica is a very popular butterfly garden plant because it has so many great characteristics. It grows fast, flowers readily all summer, is a host plant for Monarchs, and it is extremely attractive to other butterflies as a nectar plant. I hope you will consider planting some for your butterflies!

10% Off Coupon

Monarch Butterfly on Tropical Milkweed

The Milkweed plant is the sole host plant for Monarch butterflies. Although Monarchs have preferences of some varieties over others, there are many different species of milkweed plants that Monarch caterpillars will gladly gobble up. This article will present some of the best milkweeds for Monarchs, native ranges, and general information for several species.

One great thing about Milkweeds is that they double as a host AND nectar plant. As a host plant, they are only used by Monarch and Queen butterflies but as a nectar plant they are quite popular among many butterfly species.

Best Milkweed for Monarchs

Defining the “best” requires a combination of region, butterfly preference and plant performance. Different milkweed plants will grow better in various regions of the country while the butterflies “favorite” can also vary among regions (and even in the same garden from year to year).

Monarch caterpillar on a Milkweed plant

There are over 100 species of milkweeds in North America and not all of them are used by Monarchs. I will focus mainly on well-known plants that have seed available, are known to be used by Monarchs and are garden friendly (with a few exceptions that I will point out in the descriptions below).

This list is not definitive and I encourage you to try a few varieties in your garden to establish what grows well and to give your Monarchs a choice as well as back-ups. Many butterfly garden hobbyists have three or more different types of milkweed every year.

This list is a combination from experience, forum comments, and research. I welcome your own experience so I can continually refine and expand this list by preference, region, and performance. Please Contact us if you would like to share your experience.

Tiger Swallowtail nectaring on
Tropical Milkweed

Tropical Milkweed (Asclepias curassavica)

Tropical milkweed probably wins the contest for the Monarchs favorite milkweed in most gardens. It is actually not native to the US but has naturalized in zones 9-11 (possibly 8b as well) where it grows as a perennial. However, this plant grows fast and easy from seed and readily flowers all summer so is used as an annual all over the US and Canada.

It does not require cold stratification like many milkweed seeds do and it produces a lot of collectible seeds each summer. The seeds can then be winter sown or started indoors early in the spring to get a jump start on the butterfly season.

This milkweed plant may reseed itself in your garden or may even return in the spring in a protected area. It is highly recommended by many butterfly gardeners and is also a great nectar plant for many other butterflies.

For more detailed information, photos, and/or purchases please see our complete description at Tropical Milkweed (Asclepias curassavica).

Swamp Milkweed
Jennifer Anderson @ USDA-NRCS PLANTS Database

Swamp Milkweed (Asclepias incarnata)

Swamp milkweed and the next few listed below are known to be high up in the Monarchs preference list. Due to native ranges, regions and individual garden variances it is difficult to put one over another as an overall Monarch “favorite”.

Asclepias incarnata is a perennial, hardy in zones 3-8 (some reports include zone 9). It is a wetland plant but will do fine in medium moist conditions once established.

It grows easily from seed if it is cold stratified before starting indoors or Fall/Winter sowed. This milkweed is native to most of the USA and eastern Canada with the exception being the west coast. It is a nice addition to a butterfly garden and is also attractive to many species of butterflies as a nectar plant.

Swamp milkweed is not invasive as some other milkweeds are and is well behaved in the garden. We have photos, more detailed information, and seeds/plants for sale at Swamp Milkweed.

Asclepias physocarpa also known as Swan or Balloon plant
Source: Tauolunga reproduced under
Creative Commons

Swan or Balloon Plant (Asclepias physocarpa)

Asclepias physocarpa (also known as Gomphocarpus physocarpus) has many common names including Swan plant, Balloon plant, Oscar, Family Jewels, Hairy Balls and Giant Swan Milkweed.

It is popular with the Monarchs and is a very interesting milkweed in that the seed pods are round balls. The flowers are pretty but not outstanding; however, the seed pods make this milkweed plant stand out as a conversation piece! The pods are also wonderful for dried arrangements.

Family Jewels milkweed is actually native to South Africa. It is a tender perennial in zones 9-10 and in tropical areas could become weedy/invasive. It is grown as an annual in the cooler zones. Seeds can be collected in the fall and replanted in the spring.

This milkweed is a large plant reaching 5-6 feet tall with a tree like form. To see more pictures, get more information or purchase plants/seeds please visit Asclepias physocarpa.

Purple Milkweed
(Asclepias purpurascens)
William C. Taylor @ USDA-NRCSPlants Database

Purple Milkweed Plants

There are two different species of milkweed that have the common name of “Purple Milkweed”; Asclepias purpurascens and Asclepias cordifolia. Asclepias cordifolia also has the common name of Heart-leaf milkweed. Heart-leaf milkweed is native to California, Nevada, and Oregon while Asclepias purpurascens is native to central and eastern US and Eastern Canada.

Heart-leaf Milkweed
(Asclepias cordifolia)
© 2008 Keir Morse

Both of these plants are sometimes favored among butterfly gardeners because they are unique in coloring with darker flower colors of violet or purple compared to most other milkweeds. They are also well behaved in garden settings and are easily controlled. Asclepias purpurascens is similar to common milkweed (discussed below) but its flowers are much darker and it is much better behaved in the garden.

The hardiness range for Heart-leaf milkweed is zones 7-10 while Asclepias purpurascens is hardy in zones 3-8.

We have more info, pictures and seeds/plants available for Heart-leaf milkweed here and Asclepias purpurascens here

Common Milkweed
(Asclepias syriaca)

Common Milkweed is a perennial that is native to North America. This milkweed and the one described below populate “weedy” areas within their region. They are attractive to Monarchs, although, the Monarchs may be more attracted to some of the milkweeds named above if they are available.

Asclepias syriaca is native to the central and eastern half of the United States and Canada and is hardy in zones 4-9. It is easy to grow and does well in many different soil types.

Asclepias syriaca will be a good choice if you have the space for it outside of your garden. In a fertile garden without the competition of weeds it is invasive. Common milkweed will sprout up everywhere through underground rhizomes (and reseeding) and is hard to eradicate.

If you are looking for a milkweed plant to place in an ornamental garden you may want to consider a different type of milkweed (like the ones mentioned above) or keep your Common milkweed in large containers. Please visit our description of Common milkweed for more growing information and seed or plants.

Asclepias speciosa
Source: Vicki Watkins under Creative Commons

Showy Milkweed (Asclepias speciosa)

Showy milkweed is the western version of Common milkweed. It is found in the western half of the US and up into Canada. It is hardy in zones 4-9 and is a rhizomatous plant spreading underground or by seeds much like Common milkweed. As with Common milkweed, Showy milkweed can become very invasive in the garden.

Showy milkweed earns its name when it is in flower. The flowers are fragrant and quite pretty set against silvery-green foliage.

Asclepias speciosa will do well in dry conditions and poor soil. It is reported that this plant does not do well in containers unless they are 5 gallons or larger.

We have a description of Asclepias speciosa that provides much more information on growing and caring for Showy milkweed as well as seeds/plants for sale.

Female Black Swallowtail on
Butterfly Weed

Butterfly weed (Asclepias tuberosa)

Butterfly weed falls at the bottom of the list because most Monarchs prefer other milkweed plants. However, the Monarch butterflies have used it in my yard when it has been the first one up or when all other milkweed has been depleted. It is a big magnet for other butterflies as a nectar source. I really like this plant in my butterfly garden because it attracts many butterflies to its nectar and it is my backup caterpillar food.

Asclepias tuberosa is a long lived and tough perennial and is hardy in zones 3-9. It is native to most of the USA and eastern Canada. It is an easy and dependable plant once it is established and it is very well behaved in the garden. Asclepias tuberosa produces a strong taproot which makes established plants difficult to transplant but also makes the plant tolerant of dry conditions.

The Butterfly weed flowers have a bright garden presence and this is an easy milkweed I like having around. For more info, pictures, seeds and plants, please visit Butterfly Weed.

Additional Information about Milkweed Plants

There are many more types of milkweeds than I can cover here. If you have a local native-plants nursery you may want to check there for good native milkweeds in your area. Just be sure to ask about invasiveness if that is an issue for where you will be planting it. Also, I will add more milkweed plants to this list as I learn more from reader feedback or from research.

Monarch butterfly sipping nectar from Common Milkweed

One thing you should know about every milkweed plant is that it is poisonous to animals if consumed so you would not want to plant milkweed around livestock or a pet that likes to chew plants. The toxicity of the plant is what helps protect the Monarchs from predators as they do not like the taste of the caterpillars or butterflies.

Milkweeds get the “milk” in their name from the milky latex that oozes out when a leaf or stem is broken. This “milk” can cause severe eye problems if it gets in an eye. My kids and I have never had a problem with it but we are pretty strict about washing our hands after handling. Please be sure to take appropriate precautions when handling.

One more thing, plant as many plants as you have room for. The Monarchs are very good at finding a milkweed plant but the more you have in your yard, the more likely they will find it and lay their little eggs all over it! I hope you really enjoy raising Monarch butterflies. They are one of the butterfly species that is beautiful in all stages of their butterfly life cycle!

Family:

Milkweed Family (Asclepiadaceae)

Other Names:

cottonweed, silkweed, Virginia silk, wild cotton.

Origin and Distribution:

Common milkweed is a native of North America. Currently, its range includes the eastern half of the United States. Also, it has become naturalized in much of central and southern Europe. In Ohio, common milkweed is distributed throughout every county. Plants grow in clumps or patches in meadows, fencerows, roadsides, railways, waste places, reduced-tillage fields, and other open habitats. Common milkweed prefers rich sandy or gravelly loam soils that are well drained. It grows best in full sunlight or light shade. There are reports that the species does not grow well where boron is limiting.

Plant Description:

Common milkweed is a robust, erect perennial. Its stems and leaves exude a white milky sap if cut or crushed, which is a common characteristic of species in the Milkweed Family. It can be distinguished from other milkweeds by its purplish flowers that form ball-shaped clusters and large teardrop-shaped seed pods covered with warty bumps. After pods mature in autumn, they split lengthwise releasing numerous tufted seeds. Seed pods usually remain atop the dead stems throughout winter. The plant reproduces by seeds and creeping underground roots.

  • Root System:

    The root system includes a perennial crown and horizontal creeping roots.

  • Seedlings and Shoots:

    Young plants are covered with downy hairs. Young leaves are dark green, waxy, oblong, and have a pointed tip. Hairs present on the upper surface of young leaves are usually lost as the plant matures. All parts of the plant exude a milky sap when cut or crushed.

  • Stems:

    Stems emerge either alone or in clusters from a single root crown. Stems are round, hollow, stout, unbranched, covered with short downy hairs, and 2 to 6 feet tall.

  • Leaves:

    Leaves are opposite (2 leaves per node), 3 to 8 inches long, broadly oval, smooth edged, and have rounded to somewhat pointed tips and bases. The lower leaf surface is pale green and hairy compared with the upper surface, which may or may not have hairs. Leaves have a prominent white midrib and veins that resemble rungs of a ladder. Leaves attach to the stem by way of short, thick leaf stalks (petioles).

  • Flowers:

    Flowers consist of 5 downward-pointing petals and a 5-part central crown that are purplish, usually tinged with green, and have a sweet odor. Flowers are 1/2 inch wide and form 2-inch-wide, ball-shaped clusters located at the ends of stems or stalks attached to the stem at a node.

  • Fruits and Seeds:

    Seed pods are 3 to 5 inches long, 1 inch wide, gray-green, warty, and shaped like a long teardrop. As they mature, pods turn brown and split open lengthwise revealing a shiny yellow inner surface and releasing numerous brown seeds that are about 1/4 inch wide, flattened, and have a tuft of silky hair attached to one end.

Similar Species:

Common milkweed is easily confused with hemp dogbane (Apocynum cannabinum), which is a related species. However, seedlings and young shoots of hemp dogbane are smooth whereas those of common milkweed are hairy. Also, the upper half of hemp dogbane plants is more branched and its leaves and flowers are smaller compared with those of common milkweed. In addition, hemp dogbane flowers are greenish-white while those of common milkweed are purplish. Butterfly milkweed (Asclepias tuberosa) is similar in appearance to common milkweed except it has orange flowers and its sap is watery rather than milky.

Biology:

Common milkweed blooms from June to August. Seedlings do not flower until the second year. Usually, 1 or 2 flowers in each cluster mature into a seed pod. It has been estimated that a single common milkweed plant can produce 25 fruits and each fruit contains as many as 450 seeds. Seeds can float and fly and have been reported to survive at least 3 years buried in soil. Roots can grow 13 feet deep and the length of horizontal roots can increase up to 10 feet in a single season. A piece of root about 1 inch in length can produce a new plant. A common milkweed density of just over one shoot per square foot reduced wheat yields 47%. In soybean and corn, common milkweed is reported to reduce yields 19 and 10%, respectively. Cultivation can fragment and spread underground roots, which generally increases shoot numbers and population size. However, frequent cultivation or mowing depletes food reserves and ultimately inhibits roots from sprouting. Seedlings can be controlled using pre-emergence herbicide applications and some post-emergence herbicides are effective on older plants.

Toxicity:

All parts of the plant contain small quantities of potentially toxic substances. Common milkweed is toxic to poultry. Other livestock including sheep, goats, cattle, and horses can be poisoned if sufficient amounts of green or dry milkweed are consumed. Livestock usually avoid the plant unless other forage is unavailable. In humans, the plant is slightly toxic and only if eaten in very large quantities. However, it can cause contact dermatitis in some people.

Facts and Folklore:

  • Linneaus used ‘syriaca’ when naming this species because he believed it was from Syria.

  • The floss, which is 5 times more buoyant than cork and 6 times lighter and warmer than wool, has had a variety of uses such as stuffing pillows, mattresses, life preservers, and flight jackets.

  • Scientists experimented with using the milky sap as an alternative source for rubber.

  • The fibrous stems have been suggested as an alternative for flax or hemp.

  • Native Americans used common milkweed flowers in jam and, after careful preparation, young shoots were eaten like asparagus.

  • Caterpillars of monarch butterflies often feed on leaves of common milkweed. As a result, predators find both caterpillars and adult butterflies distasteful and generally avoid eating them.

Each year since 1990, the Perennial Plant Association has designated a “Perennial Plant of the Year.” The designation has become well known amongst growers, landscapers, gardeners, and others who eagerly await the announcement each year. Selection often launches the chosen plant into the mainstream, making it more widely available. While the association has often favored non-native ornamentals, for 2017 they have selected a native milkweed, commonly known as butterfly weed (Asclepias tuberosa).

Milkweeds (Asclepias spp.) are the required host plants for caterpillars of the monarch butterfly and thus play a critical role in the monarch’s life cycle. The loss of milkweed plants in the monarch’s spring and summer breeding areas is believed to be a significant factor contributing to the decline of monarch populations across North America. Over the past several years, the Xerces Society and others have been raising awareness of milkweed, working with growers to increase availability of seeds and plants, and urging gardeners in critical breeding areas to plant it. Though there are 73 known species of milkweed in North America, many of these species are rare, threatened, or endangered.

Butterfly weed (Asclepias tuberosa), the 2017 Perennial Plant of the Year. Photo: Derek Ramsey via Wikimedia Commons.

We can see why butterfly weed, with its broad range, vibrant orange flowers, and garden-friendly habit would be the milkweed of choice for Perennial Plant of the Year, but, like any plant, it needs the right conditions to thrive and may not be the best pick for every garden.

Read on to learn more about butterfly weed, as well as some alternatives you should know that may be better suited for your specific region or growing conditions. For more options visit xerces.org/milkweed/ where you can find region-specific milkweed guides.

Butterfly Weed

2017 Perennial Plant Pick

Growing to a manageable height and spread of only 1’ to 2’, butterfly weed (Asclepias tuberosa) is easy to find a home for in even the smallest garden. Its unusual bright orange flowers are striking, especially when visited by green metallic sweat bees who are frequent visitors.

Butterfly weed is native to much of the lower 48 states and eastern Canada. It is not native to the northwest. Butterfly weed requires full sun, and dry well-drained soils. Butterfly weed does not perform well in heavy clay, richly amended garden soils or wet areas where its taproot will be prone to rot and the plant may not be reliably perennial. Its taproot makes it difficult to transplant, so be sure to pick a spot where you’ll want to enjoy the plant for years to come.

Green metallic sweat bees (Agapostemon spp.) are frequent visitors to butterfly weed where they stand in stark contrast against the orange flowers. Photo: Justin Wheeler

Swamp Milkweed

Makes a Splash in Most Any Garden

Despite its ugly name, swamp milkweed (Asclepias incarnate) is a knockout, and one of the easiest to grow milkweeds. Though the common name refers to the fact that it is often found in wet areas, at the edge of river-banks or low spots in meadows, it will tolerate a surprisingly wide range of soil types though may need supplemental watering in drier areas.

Swamp milkweed has a broad range, occurring in almost every state east of the Rockies from Northern Canada to Florida. Swamp milkweed grows to a height of 3’ to 4’ and will form small colonies where conditions suit. Though it prefers full sun it is one of the more shade tolerant milkweeds and can take partial sun. The soft pink, lightly scented flowers are large and showy, and the lance-shaped leaves are well enjoyed by monarchs. Some have observed that monarchs seem to prefer the leaves of swamp milkweed over those of butterfly weed when both are present.

Sometimes called rose milkweed, the lightly scented, soft pink flowers of Asclepias incarnata make a lovely addition to any garden. Photo: Justin Wheeler

Common Milkweed

Commonly Loved by Monarchs

Common milkweed (Asclepias syriaca) has a bad rap, as it’s known to be more aggressive than other milkweed species. It’s tendency to form colonies and readily re-seed can make it problematic in a garden setting. Still, studies have shown that it is the most frequently used host plant where its range overlaps with the monarch’s breeding areas, and as it’s rapidly disappearing from critical breeding habitat, it should be tolerated wherever it decides to pop up or embraced as a valuable addition to your garden. With one of the largest flower clusters and a tall sturdy stem, it can be a real “design feature” and should be considered a gift to your garden, rather than a nuisance.

When planted in shallow, compacted soil such as the kind found in parking strips, common milkweed often maintains a more manageable height and spread. Photo: Wikimedia Commons

Showy Milkweed

The Star of the Show

For those lucky enough to live within the range where it grows, showy milkweed is arguably the most attractive of our native milkweeds. Growing to a manageable 1’ to 3’, it features a stout, upright stem with closely clasping, velvety, gray-green leaves. The real “star” of the show, however, is the showy spherical bloom. Unlike other milkweed species where the flower clusters display in a more open habit, showy milkweed blooms in tight clusters of prominently star-shaped flowers. Showy milkweed is beautiful enough to stop traffic, and more than a few passing monarchs.

The unique star-shaped flowers of show milkweed are attractive to humans and pollinators alike. Photo: Matt Lavin CC BY-SA 2.0

Narrowleaf Milkweed

Grows Where Others Can’t or Won’t

Naturally occurring on dry sites in plains, valleys, roadsides, and disturbed grounds in the west,- narrowleaf milkweed (Asclepias fascicularis) is drought and heat tolerant while being much-loved by monarchs. Often found in areas that may experience drought followed by seasonal flooding, it’s an ideal choice for rain gardens and rain catchment systems. As the common name implies, the plant features long, narrow, often heavily drooping leaves and a narrow stem. It often makes up for its wispy form by growing in dense clumps where its slender silhouette, in combination with several others, creates an airy mass topped by light pink flowers.

A monarch caterpillar enjoying the leaves of Asclepias fascicularis, Photo: The Xerces Society / Stephanie McKnight

Planting Milkweed in the Fall

The perfect time to sow native milkweed outdoors is right when Mother Nature does it, in the fall! Exposure to cold temperatures and moist conditions during winter will stimulate germination. Spring planting is also possible but artificial stratification of the seed is recommended to enhance germination. (Click here to read how to plant milkweed in the spring.)

You can purchase these native milkweed seeds directly from Butterfly Lady at http://butterfly-lady.com/marketplace/seeds.html

Choose your Area

Native milkweeds need full sun to grow so make sure the area you choose has at least least 6-8 hours of sun per day.

There is a reason the milkweed plants are not doing well in this butterfly garden. Milkweed needs full sun to thrive.

Prepare the Soil

Like all wildflowers, milkweed should be planted on bare soil. Remove existing plants and weeds and then rake the soil up to remove large rocks and other debris. Make sure there is no existing growth in the area before planting, so the milkweed seeds won’t need to fight underneath the surface to establish their roots.

I commandeered some neighborhood kids to help me prepare the garden bed.

Sow the Seeds

Be sure to wait until the first killing frost to sow the seeds. Space the seeds out one by one about 10-12 inches apart. If you have a large area and a quantity of seeds you can simply throw them out by the handful. If you do scatter them loosely by hand, come spring when the seeds start to germinate you may want to thin them out if they are extremely close together.

Do not cover the seeds! Simply press them against the soil with your hand or the sole of your shoe. If you’re seeding a large area you could also use a seed roller. Milkweed seeds require light to germinate, so if you cover them with soil, they won’t germinate come spring.

Soil is ready for the seeds.

WATER

Once you’ve pressed the seeds into the soil, give the area a good watering to set the seeds. Because you’re planting in the fall, you won’t need to water after this until early spring when the seeds start to germinate.

Walk Away

Now walk away and forget about them and let Mother Nature do her magic. As winter progresses, they’ll naturally be exposed to the eight to ten weeks of cold temperatures required for them to germinate when spring arrives.

Spread the message and wear this “Plant Milkweed” t-shirt created by Butterfly Lady. https://amzn.to/2PFvZn4

How to harvest and plant milkweed seeds

Support monarch butterflies with milkweed

Want to help stop the decline of monarch butterfly populations and bring more of these fluttering beauties back into your garden? Plant milkweed —  it’s the sole food source for monarch caterpillars and is attractive to many pollinators for its nectar-rich flowers.

Growing milkweed

You can plant milkweed starter plants purchased at specialty nurseries. Any species in the milkweed family will do, but the easiest to grow is the common milkweed, Asclepias syriaca. Plant them in full sun in groups of three to six spaced 6 to 24 inches apart scattered around your garden. Smaller groupings are less prone than mass plantings to insect or parasite infestations or predators.

It’s also easy to collect milkweed seed (be sure to ask property owners first) and start it yourself. See the gallery at the bottom of the article for our tips on how to collect seeds.

Planting milkweed seeds

Milkweed seeds need to be stratified to help them germinate. Stratification is when a seed is moistened, chilled or frozen and thawed, breaking down germination inhibitors on the seed coat, such as waxes, hormones, oils or heavy coats. Milkweed seed planted in fall is naturally stratified. Spring-planted seeds need to be chilled in the refrigerator, which replicates the natural process of snow and cold breaking down the seed casing.

Learn more about prechilling seeds before planting

Fall seed planting

Plant seed in fall in a sunny location. Simply sprinkle seeds on well-tilled soil and pat them down, add a topdressing of soil, and water them in. Fall-sown seed will be naturally stratified outside.

Spring seed planting

You can plant milkweed seeds in early spring as soon as the soil can be worked, but they will need to be stratified for 2 to 3 months in the refrigerator before planting in spring for better germination.

When emerging milkweeds have three to four sets of leaves, thin seedlings to 6 inches apart.

Starting seeds indoors in winter

You can also start stratified seeds indoors in late winter. Sow 2 to 3 seeds in a pot filled with seed-starting mix, cover with ¼ inch of mix, water lightly and set under lights. Germination takes 7 to 10 days. Plant seedlings outside in a sunny spot when they have 3 to 4 sets of leaves and the ground is warm.

Did you know you should sow these perennial seeds in fall?

Milkweed Seed Finder  

Photos, left to right: Monarch caterpillar on swamp milkweed (Xerces Society / Stephanie McKnight); Bumblebee on butterfly milkweed (Xerces Society / Sarah Foltz Jordan); Monarch over showy milkweed (Xerces Society / Stephanie McKnight)

Native milkweeds (Asclepias spp.) are essential for monarch butterfly (Danaus plexippus) caterpillars and support a diversity of pollinators with their abundant nectar. By including milkweeds in gardens, landscaping, wildlife habitat restoration projects, and native revegetation efforts, you can provide breeding habitat for monarchs as well as a valuable nectar source for butterflies, bees, and other beneficial insects. As part of our Project Milkweed, we have created this comprehensive national directory of milkweed seed vendors to help you find sources of seed. To learn more about monarch butterflies and how you can participate in conservation efforts, please visit the Xerces Society’s Monarch Butterfly Conservation page or the Monarch Joint Venture webpage.
Please scroll down to use the search feature. We also advise you to read the important considerations detailed here:

When Using the Milkweed Seed Finder, Please Note:

  • Milkweed seed is currently unavailable in several areas of the country. If you do not receive any results when you search by state, we have not learned of any milkweed vendors located there. Please search other states in your region for vendors who may carry local ecotype seed that is appropriate for planting in your area.
  • A seed vendor’s physical address does not always reflect the origin of the seed that they carry. Please always ask vendors for information about seed origin and try to plant seed that is as locally sourced as possible.
  • Some of the vendors listed are wholesale only and require a minimum order amount.
  • In most parts of the country, it is best to plant milkweed seed in the fall; however spring planting is possible in some areas. Please ask your regional seed vendor for planting recommendations.

Milkweed Availability and the Nursery Industry

At present, nearly 40 milkweed species are available as seed to varying degrees, although availability varies widely by region. Through Project Milkweed, we have been working to change this in several states, but notable gaps in availability remain.
In addition to seed, several nurseries also sell milkweed transplants (“plugs”). Please ask your regional vendors about availability. For regional lists of native plant nurseries, visit our Pollinator Conservation Resource Center.

Species Selection

We encourage you to only plant milkweed species that are native to your area. The Biota of North America Program’s (BONAP) web-based North American Plant Atlas provides county-level distribution information for all Asclepias species in the lower 48 states (milkweeds are not native to Alaska and Hawaii). Please refer to BONAP’s map color key for detailed information, and note that dark green indicates that the species is present within the state, while bright green shows that the species is documented to occur in that specific county. However, these maps do not convey the abundance of the species within each county.
For recommendations of which species to plant on a regional basis please download this fact sheet by the Monarch Joint Venture.
Three Asclepias species have been introduced to the United States: tropical milkweed (A. curassavica), African milkweed (A. fruticosa), and swan or balloon plant (A. physocarpa). Of these, tropical milkweed (also called blood flower or scarlet milkweed) is the most widely available from commercial sources. However, there is preliminary evidence that where tropical milkweed has been introduced, its presence may cause monarchs to reproduce outside of their regular breeding season, disrupt monarchs’ migratory cycle, and increase transmission and virulence of the protozoan parasite (Ophryocystis elektroscirrha). Thus, some monarch scientists are concerned that the planting of tropical milkweed may lead to negative impacts on monarch health. For more information on this topic, please download this fact sheet by the Monarch Joint Venture or read this Q&A, also from the Monarch Joint Venture, about research related to tropical milkweed and monarch parasites.

Seed Sourcing

An ecologically responsible approach is to use seed that is sourced as locally to your property or project site as possible. Milkweed seed can be purchased on the internet from multiple vendors but given some species’ broad distribution across the United States, available seed may be of non-local origin. While some seed companies specialize in locally native seed, many do not advertise seed origin or ecotype, and it should not be assumed that seeds have been collected or produced in the region in which a vendor is located. To identify sources of regionally appropriate seed, please ask prospective vendors for information about seed origin. If milkweed seed is completely unavailable within your region, yet milkweeds are integral to your planting plans, you could consider making arrangements to have seed wild-collected from local populations.

Successful Milkweed Establishment

Successfully establishing milkweed requires some very specific steps. Please refer to our Project Milkweed page for more information on successful milkweed establishment. For those working to Save Western Monarchs by planting milkweed in California, please refer to our fact sheet Native Milkweed in California: Planting and Establishment.

For Seed Vendors

If you are a milkweed seed producer or a native seed company that offers milkweed seed and would like to either be added to this directory or request changes to your vendor entry, please contact us at .

Questions?

Please see our Milkweed FAQ page, or contact .

UConn Home & Garden Education Center

Milkweed
Asclepias

Printable PDF
Click on images to see larger view
Baltimore checkerspot, Bombus flavifrons, and Great spangled fritillaries on common milkweed
Milkweed is the common name for many plants in the genus, Asclepias. In the northeast, there are five different perennial species of milkweed growing wild: butterfly weed (A. tuberosa), common milkweed (A. syriaca), poke milkweed (A. exaltata), swamp milkweed (A. incarnata), and whorled milkweed (A. verticillata). All are suitable hosts for the monarch and many other caterpillars and insects.
The association of the monarch butterfly and the milkweed plant is pretty well-known. This is because the monarch butterfly will only lay its eggs on Asclepias species, which are the only host plants of its caterpillar. Milkweeds also serve as a nectar source for many butterflies and many other pollinator insect species, and for this reason, milkweeds are great plants to include in both butterfly and pollinator gardens.
Two monarch caterpillars on common milkweed Several monarch caterpillars on swamp milkweed
All milkweeds contain a milky sap which can be seen if the stem or leaf is broken. Within the sap is a toxin, cardiac glycosides, causing poisoning of humans and animals if eaten. Some insects have evolved over time to become adapted to feeding on these toxins, and the insects become poisonous to the predators that eat them. The insects have developed a way to take the toxins from the milkweed while eating the leaves and sap, and use the toxins as a defense mechanism against birds, animals and other insects that want to use them as a food source.
Site Selection
Milkweed plants will grow in slightly acidic soil with a pH range from 4.8 to 6.8. They are hardy in zones 3-8. Milkweed plants require full sun and a lot of space and should be placed at the back of flower beds as they can grow to 3 feet tall. The planting site should be chosen carefully as milkweed is difficult to transplant.
Planting
Milkweed can be grown from seed or transplants. The seeds of Asclepias develop in large green pods that turn brown when seeds have matured. The seeds are arranged in rows that overlap and each pod may contain hundreds of seeds. Each seed has filaments attached to it that enable it to waft on the wind. Milkweed seeds should be harvested at a particular stage of pod opening to ensure seeds are viable. Pods should be brown, dry and open, or open when pinched at the seam. Since milkweeds are clonal, collect seeds of the same species from different areas to ensure genetic diversity.
The seeds of the Asclepias plant must undergo a process called stratification in order to germinate. To stratify milkweed seeds:

  • Remove the filaments from the seed.
  • Place the cleaned seeds into moist soil in a pot or between moist paper towels in a plastic bag.
  • Place it in a cold spot in the refrigerator for 3 weeks to 3 months.
  • Direct sow these seeds in the spring or start indoors 4-6 weeks before the seedlings will go outside.
  • When the seedlings have 4 true leaves they can be transplanted.
  • Seeds may also be planted directly in the ground in late fall.
  • Space plants 1-2 feet apart.

Some Common Asclepias Varieties
Photo from https://www.ius.edu/herbarium/dicots.php
Butterfly weed, (A. tuberosa) has orange flowers and prefers to grow in dry, gravel laden soil in full sun. It is a very drought tolerant native. Plants grows one to two and half feet tall on thick, hairy stems with lanceolate shaped leaves arranged alternately. The leaves are about one inch wide and three and half inches long. The many small, orange flowers are grouped into an umbel, giving a splash of bright color in the wild or when planted in a garden. This milkweed has a large taproot that once the plant is mature, will send out side roots to create new plants off of the original mother plant. Butterfly weed does not produce the milky sap in its leaves, so it is not commonly called a milkweed just butterfly weed, even though it is in the Asclepias genus. It is a butterfly magnet. Recommended pH is 5.6 to 7.5.

Common milkweed (A. syriaca) is aptly named as it is the most widely found milkweed in North America. It grows a strong, three foot stem and pink flower. It can be found in sunny meadows and wastelands with well drained soils. Its rhizomes spread horizontally and clonally creating large clumps of populations, and for this reason it is very difficult to successfully transplant this milkweed. One plant can have a very large root system and many stems. Its sweet scented flower attracts many butterflies and pollinators. Monarchs are a common site as well as great spangled fritillaries, red admirals, Baltimore checkerspots, coral hairstreaks and other native butterflies. Milkweed beetles and milkweed bugs are an almost constant presence on the common milkweed plant.

Poke milkweed (A. exaltata), flowers are white to lavender umbels. The umbels weep downward with flowers hanging down on distinct light green, two and half inch long petioles. The striking flower formation is very open compared to the tightly held flower formation the other milkweeds. Seed pods are held in an upright fashion, forming after flowering for about four weeks during the summer. Flowers are very strongly scented when in full bloom. Poke milkweed can be found on forest edges with moist, dappled shade conditions.
Swamp milkweed (A. incarnata), the species’ name ‘incarnata’ is from Latin meaning flesh-colored, describing the rosy flesh color of the flower. Swamp milkweed can be found in moist areas with sunny openings such as swamps, marshes, stream banks and other fresh water edges. It is suitable for gardens where it will not dry out. The leaf of the swamp milkweed is a narrow lance shape, different than the wider, rounder shape of the common milkweed’s leaf. The seed pod of swamp milkweed is also long and elegantly narrow. Recommended pH is 5.8 to 6.8
Photo from https://www.flmnh.ufl.edu/butterflies/plants/tropical_milkweed.htm
Tropical Milkweed, (A. curassavica), can be planted as an annual in areas with cold winters. It is a great container plant placed on decks, in hanging planters or patio gardens to observe the many butterflies and nectar feeding insects that will visit the orange, red and sometimes yellow flowers. Tropical milkweed will not live through our winters and dies with the first frost. Potted plants are available at garden centers, or start your own plants easily from seed inside in early spring. It is a long bloomer, but will not keep monarchs from migrating as some have previously reported in hot season climates. Place in a full sun location for flowers all summer into early fall.
Photo by Christopher Noll, http://wisplants.uwsp.edu
Whorled Milkweed (A. verticillata) prefers to prairies, meadows and open sunny areas, often growing alongside wild grasses in ditches and wastelands. Whorled milkweed has very narrow, two to three inch long leaves occurring in whorled groups of four to six on the erect, two foot tall stems. When not in flower, the green leaves and stems almost look like grass plants. Umbels of white to greenish flowers are borne at the center leaf axis of the upper leaf whorls. Each umbel consists of seven to twenty individual flowers. Each flower is hooded has five petals and five hoods with horns. Brown seed pods are long and narrow.

Insects Associated with Milkweeds

Most insects that feed on the milkweed plant reap the benefits of the alkaloid toxin sap, storing it in their bodies to protect them against predators. Many of them have bright orange-red and black markings that also serve as a warning to shared predators.
Aphid-There are several aphids that are pests to Asclepias the most common is the yellow milkweed aphid. These piercing and sucking insects will feed on the plant’s sap and excrete the liquid called honeydew that may attract ants which harvest the honeydew. Do not confuse the bright yellow milkweed aphid, which will be mobile, with the eggs of the Monarch butterfly, which will be stationary and are generally laid in large groups.
Aphids
Milkweed leaf beetle (Tetraopes tetrophthalmus)-1/3-2/3″ long. A bright orange-red long-horned beetle with black spots. It overwinters in the soil in the larval stage feeding within the milkweed root. They pupate in the spring in earthen chambers and emerge as adults in early summer. As adults they feed on the leaves, buds, and flowers.
Milkweed leaf beetle
Large Milkweed bug (Oncopeltus fasciatus)-3/4″ long adults are bright orange-red with black wing pads and a black band across the back. Feed mid-late summer. Migrate south at the end of the season. No significant harm to the plants.
Large milkweed bug Large milkweed bug-adults and nymphs
Lesser (small) Milkweed bug (Lygaeus kalmii)-1/2 ” long adults have an orange-red X on a black background. It is often mistaken for the Boxelder bug. It overwinters as an adult or nymph. No significant harm to the plants.
Lesser milkweed bug Boxelder bug
Milkweed tussock moth (Euchaetes egle)-The orange, black and white caterpillar of the Milkweed tussock moth will be found feeding in groups of up to 10 larvae where the Monarch caterpillar is generally a solitary feeder. These caterpillars have long tufts of white and black hair along their bodies and at the ends.
Milkweed Toxicity to Livestock
(Prepared by Joyce Meader, UConn Extension Dairy/Livestock Educator)
Animals usually do not eat milkweed unless good forage is scarce. The milky white sap is sticky and has a bitter taste but livestock will eat the topmost, tender leaves if good forage is not abundant. While the fresh, green plant material is the most toxic, dried plants present in pastures or hay retain their toxicity. Cardiac glycosides are found in the majority of milkweed species, while a neurotoxin is specific to the whorled-leaf types. Of the two, the neurotoxin is the most lethal. Milkweed can be controlled with 1.5% glyphosate as a spot spray when plants have reached the late bud to flower stage of growth (will kill grasses as well).

  • Toxicity Rating: Low to moderate. Milkweed are unpalatable and have variable toxicities. Death is not likely unless large quantities are consumed.
  • Animals Affected: All animals may be affected. Sheep are most at risk, but cattle, goats, horses, poultry, and pets are also at risk.
  • Dangerous Parts of Plant: Stems, leaves, roots.
  • Class of Signs: Gastrointestinal irritation (primarily vomiting and diarrhea), incoordination, tremors, heart problems, respiratory difficulty, death.

Despite good cultural practices, pests and diseases at times may appear. Chemical control should be used only after all other methods have failed.
For pesticide information or other questions please call toll free: 877-486-6271.
UConn Home and Garden Education Center, 2018
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, the Dean of the College, Cooperative Extension System, University of Connecticut, Storrs. The Connecticut Cooperative Extension System is an equal opportunity employer and program provider. To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, Stop Code 9410, 1400 Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964.

Leave a Reply

Your email address will not be published. Required fields are marked *