Plant Profile: Milkweed

Milkweed - Asclepias spp. (tuberosa, asperula, incarnata, speciosa)                                     

Other Common names:  Antelope horns, silkweed, swallow-wort

TANTALIZING TIDBITS

  • Named for the milky secretion found in the stems & leaves

  • Source of nectar for moths and hummingbirds

  • Sole food source for Monarch butterfly larvae & caterpillar

  • Used by humans for food, medicine, fiber

  • Thomas Edison tested milkweed latex for making rubber

  • Used in WWII to fill life jackets (kids picked 25,000 million pods to help with effort)

BOTANICAL DESCRIPTION

At 3-5 feet tall, these stout beauties grow a thick stem (similar to a cornstalk, but smaller) with a faint covering of hairs, and choose not to waste energy on branch-making, perhaps devoting their growing energy to their spectacular flowers.  The thick and narrowly tapered leaves grow opposite on the stem and sport a velvety layer of trichomes - leafy hairs on the undersides of the leaves - that help protect the plant from predators.  Milkweed harbors an important protection: a toxic white milk-like latex circulates through the stem and the leaves.  

Milkweed leaves are large, thick,  and slightly hairy. They grow opposite on the stem. 

Milkweed leaves are large, thick,  and slightly hairy. They grow opposite on the stem. 

Milkweed flowers are intricately complex and unusual with an addition of a ‘hoods and horns’ floral structure that forms the corona. The five hoods each enclose a horn which is a modified filament of the anther.  Some of the horns are visible on some species and nearly invisible on others.  

Do you see the five horns in the five hoods?

Do you see the five horns in the five hoods?

Many of the flowers have an incredible and enticing sweet floral fragrance - I can’t resist smelling them each time I am in the garden! The flowers bloom from May - Sept and attract many pollinators. Native bees, wasps and ants adore the floral nectar and various ‘milkweed’ butterflies land lightly to gracefully sip the nectar. On a mid-day summer morning, my milkweed patch is a fascinating study in pollinator and flower relationships...which explains why I have many photos of the ancient feeding and reproductive strategies.

Pollinators and nectar seekers. Once pollinated, the flowers droop and begin the fruit/seedpod development.

Pollinators and nectar seekers. Once pollinated, the flowers droop and begin the fruit/seedpod development.

And then, like the butterflies that feed from milkweed, the flower transforms into its own version of a chrysalis - a hairy warty seedpod (milkweed fruit) that shelters the thin brown seeds attached to silky and buoyant filaments called coma. The pods await the proper timing from nature (is it the changing light? The colder temperatures?) to split open along their only suture, releasing the seed parachutes to drop below the mother plant or on a windy autumn day, to seek out their own patch of soil to rest during the winter and germinate in the spring.

A newly opened seed pod with seeds attached to the coma.

A newly opened seed pod with seeds attached to the coma.

MILKWEED IN THE FIELD

The 140 or so species of Asclepius are named after the Greek God of Healing, perhaps under a mistaken identification of a similar plant from the dogbane family. While not exclusive to the New World, the majority of species are found in North America though several species have naturalized in Europe and Asia.

The genus originated in the tropics and adapted its way north so that it is now a hardy perennial plant found in temperate gardening zones 3 to 11 and can be found in every region of North America.  They aren’t picky about where they plant their feet; they can live in sandy, clayey or rocky soil. The diverse number of species live in a corresponding diversity of landscapes: wetlands, along rivers, in the desert, in mountain meadows, and other sunny spaces of undisturbed land. In my region, I see milkweed in the gravelly ditches along rural roads, in unmanaged pastures and in an occasional meadow.

This free image did not identify it as Common Milkweed (A. syriaca) but it looks like those in photos where the species is identified.

This free image did not identify it as Common Milkweed (A. syriaca) but it looks like those in photos where the species is identified.

Common milkweed (A. syriaca), native to land east of the Rocky Mountains, was called common because its multiple reproductive strategies ensured that an abundance of milkweed would be found in prairies, meadows and undisturbed land, making it easily available to the Monarch butterfly.  Habitat destruction and herbicide use are rapidly eliminating milkweed from wild places, a contributing factor in the decline of monarch butterflies.

The website Monarch Watch explains in detail:

Milkweeds and nectar sources are declining due to development and the widespread use of herbicides in croplands, pastures and roadsides. Because 90 percent of all milkweed/monarch habitats occur within the agricultural landscape, farm practices have the potential to strongly influence monarch populations.

Development - Development (subdivisions, factories, shopping centers, etc.) in the U.S. is consuming habitats for monarchs and other wildlife at a rate of 6,000 acres per day - that's 2.2 million acres each year, the area of Delaware and Rhode Island combined!

Genetically Modified Crops - Widespread adoption of herbicide-resistant corn and soybeans has resulted in the loss of more than 80 million acres of monarch habitat in recent years. The planting of these crops genetically modified to resist the non-selective systemic herbicide glyphosate (Roundup®) allows growers to spray fields with this herbicide instead of tilling to control weeds. Milkweeds survive tilling but not the repeated use of glyphosate. This habitat loss is significant since these croplands represent more than 30% of the summer breeding area for monarchs.

Roadside Management - The use of herbicides and frequent mowing along roadsides has converted much of this habitat to grasslands - a habitat generally lacking in food and shelter for wildlife. Although some states have started to increase the diversity of plantings along roadsides, including milkweeds, these programs are small.

Unfortunately, the remaining milkweed habitats in pastures, hayfields, edges of forests, grasslands, native prairies, and urban areas are not sufficient to sustain the large monarch populations seen in the 1990s. Monarchs need our help.

MILKWEED IN THE GARDEN

Like some undisciplined gardeners, I was seduced by a seed catalog’s photo of Showy Milkweed (Asclepius speciosa) in bloom. I ordered the seeds and sowed them into the corner of my L-shaped herb/pollinator bed within my fenced vegetable garden.  Shortly after that I mentioned to another experienced gardener that I introduced milkweed to my garden and she responded with, “You may regret that. You know it’s invasive.”  The word ‘invasive’ raises a high level of fear and anxiety in a gardener’s mind; anyone who has spent hours pulling mint, bamboo or lemon balm from an area meant to be shared with other plants understands the power of that word.  I searched online for confirmation of her statement and found an occasional reference to it slowly spreading via its underground stems (rhizomes). Slow spreading is manageable so I anticipated a bit of removal here and there. My milkweed also reproduces sexually via an array of pollinators visiting flowers, moving pollen grains around, resulting in a seed pod, filled with seeds to be dispersed by the wind.

That made me curious: why does it produce both seed and spread underground, creating clones of the original plants? I couldn’t find a specific answer other than it is simply a biological advantage for some plants to have multiple reproductive strategies.

My milkweed patch in the middle of my fenced vegetable garden.

My milkweed patch in the middle of my fenced vegetable garden.

The end result of my planting is a towering patch of beautiful milkweed plants that send out several clones each year to expand its colony.  Some I leave and those that pop up in the surrounding paths are pulled. Given its fragrance, beautiful flowers, its ability to attract many different pollinators to my vegetable garden, and its multiple uses for human use, milkweed has easily earned its dedicated space.  And with any luck, the wind-dispersed seeds will take up residence in my unused pasture (note: most milkweeds are poisonous to grazing livestock so they should not be planted where horses, cattle or sheep can eat them). But the best reason to plant native species of milkweeds is to offer nectar to native bees, wasps and butterflies and to provide food for the Monarch caterpillar.

Monarch caterpillars eat exclusively on toxic milkweed leaves; the caterpillar's ability to adapt to the toxins by sequestering them is key to the specialized relationship between milkweed and monarchs.

Monarch caterpillars eat exclusively on toxic milkweed leaves; the caterpillar's ability to adapt to the toxins by sequestering them is key to the specialized relationship between milkweed and monarchs.

Due to the continuing decline of Monarch populations, many well-meaning folks put out a call to gardeners to plant milkweed without recommending the importance of planting milkweed native to their regions and landscapes.  Xerces, a non-profit dedicated to the conservation and protection of invertebrates and their habitats, has created several excellent Regional Milkweed Guides and other tools to help gardeners and conservationists select native milkweeds for their regions. Check out their Project Milkweed.

There are 11 species of insects that attack various  milkweed plants, which is fascinating given the toxic latex.  Some of them are the usual garden suspects like Japanese beetles and aphids. You can learn more about milkweed pest  at Monarch Butterly Garden.
 

MILKWEED IN THE KITCHEN

First, I must confess I am not much of a wild foods eater.  I grow cultivated vegetables because that’s what I like to eat. But I am interested in wild foods from a survivalist perspective: when the zombies arrive or the grid goes down or I get lost on a hike, I want to know what is edible and how to prepare it.

Warning: Milkweeds contain cardiac glycosides that are toxic to humans when consumed in large amounts. Never consume any part of milkweed raw! The glycosides are found throughout the plant and levels of toxicity vary by species. Thoroughly research and observe the correct ways to harvest and prepare milkweed to avoid the toxins.

Indigenous people and wild food enthusiasts select the immature stems and seedpods and plunge them into boiling water for several minutes and then cook according to the recipe. Some foragers recommend blanching the plant parts several times, discarding the water each time.  The glycosides are quite bitter and Euell Gibbons referred to the blanching protocol as “taming the bitterness.”

STEMS: In late spring, cut emerging shoots (stems) when they are less than 8 inches high and cook and eat like asparagus.

young seed pod.jpg

PODS: Pods must picked at an early stage (2 inches or smaller) and boiled several times. Cook and eat like potatoes.  The pods can be stuffed like pasta shells and can also be fried like okra. Hunger and Thirst offers several interesting recipes.  (I may try them next summer but I would have to lie to the other human in the house.)

Milkweed flower buds

Milkweed flower buds

FLOWER BUDS: Harvest when they are just forming and before they turn pink. Cook and eat like broccoli. Most foragers dare you to tell the difference from broccoli!

LEAVES: the youngest leaves (at the top of the growing plant) can be harvested, blanched and cooked like spinach.

FLOWERS: If you like sweet floral flavors, you will enjoy Milkweed Flower Syrup.  This can be mixed into cocktails, mocktails and used as a topping on baked goods, ice cream.  The recipe is easy and can be found at The Backyard Forager.  

Note: Because of the decline in milkweed populations, foraging for wild milkweed plants should be discouraged.  If you want to eat milkweed, grow a milkweed patch.

 

AS FIBER,  DYE & AN INDUSTRIAL CROP

Like hemp, dogbane, flax and nettle, the bast fiber of milkweed stalks (stems) have been used used to make cord, rope and fabric for thousands of years. The bast fibers are found along the inner bark once the pithy center has been removed. Making cordage is easy and an interesting craft but there are numerous steps. The bast fibers can also be spun to make yarn.  

Coma - white filaments with seeds attached, creating a wind-borne reproductive strategy.  Often called seed parachutes.

Coma - white filaments with seeds attached, creating a wind-borne reproductive strategy.  Often called seed parachutes.

Some spinners have attempted to spin the coma (the silky filaments in the seedpod) but claim it is too brittle on its own but can be combined with other natural fibers to create yarn.  In the past, the fibers have been used to make candle wicks.

Educational and motivational comic used to encourage American children to collect mature seed pods.  Photo: USDA/Conservation Service

Educational and motivational comic used to encourage American children to collect mature seed pods.  Photo: USDA/Conservation Service

But those filaments are far more useful in other ways: hollow and coated with a natural wax, the buoyant 'seed floss' repels water and absorbs oils. During WWII, American children went to the fields and picked 25 million pounds of pods for manufacturers who extracted the floss and filled lifejackets for the US Navy.

Collected milkweed pods to be used used for stuffing life jackets for the US Navy  Photo credit: USDA/Conservation Service

Collected milkweed pods to be used used for stuffing life jackets for the US Navy  Photo credit: USDA/Conservation Service

Today, milkweeds are grown commercially and the white filaments are used in floating cleanup kits for oil spills and to make insulated winter garments and bedding like pillows. The pods contain an oil that is mechanically extracted and used in commerce. The fat-rich seeds are expeller pressed into a nutritious oil that can be used as a moisturizer. The defatted seeds are ground into a meal and are used to kill nematodes and army worms.  

My three plant dye books do not list Asclepias spp. as a natural dye for fibers but there are several references online that do.  However, the problem is they do not identify by the scientific name.  Some milkweeds may produce green or yellow dyes but I don’t know which ones do.  Below is a recipe from Herbalpedia that does not identify the species but claims that milkweed will produce a bright yellow dye.

Dye Recipe: 1 pot milkweed, leaves, stems, flowers and/or pods 1 lb alum mordanted wool 1⁄4 cup clear ammonia 4 gal water

Boil the cut-up milkweed in water for about 1 hour. It may be necessary to add additional water so it won’t boil dry. Cool and strain out the leaves, etc. Add the ammonia and enough water to make 4 gallons. Enter the premordanted wool and raise slowly to simmer and hold it there for 3⁄4 hour. Remove the wool immediately from the dye bath and rinse in hot water. If you don’t rinse the milkweed right away it may develop dark spots. Color: bright yellow

MILKWEED AS MEDICINE

WARNING: Because of the varying levels of the toxic cardiac glycosides in Asclepius species, it’s important to not use milkweed medicinally without careful research and in some cases, supervised by a clinical herbalist.  

Many of the milkweed species have been used for medicinal purposes by North American Indigenous people.  Here are some of the traditional uses for milkweed species:

Milky Latex Secretion

  • Used topically for warts (contains asclepain - proteolytic enzyme)

Roots

  • Pleurisy root (A.tuberosa) - cough remedy still used today for pleurisy; listed in the US Pharmacopeia from 1820 -1905 & then in the National Formulary from 1906 - 1936 as a treatment for pleurisy

  • The root is emetic and cathartic in large doses. Tinctures were prepared as emetics to induce vomiting in case of poisoning.

  • Milkweed root is considered a diuretic, expectorant and diaphoretic. Herbalist Michael Moore states it “softens bronchial mucus and dilates bronchioles” and “stimulates urine and perspiration”.
  • The toxic cardiac glycosides, when properly dosed, can support and strengthen heart health. Heed the earlier warning about using milkweed as internal medicine without proper research.

MILKWEED & MONARCHS: A TOXIC RELATIONSHIP

Monarch butterfly visiting a milkweed.

Monarch butterfly visiting a milkweed.

The relationship between milkweed plants and monarch butterflies is a toxic one.  Milkweed's bitter cardiac glycosides, found in the milky secretion that flows throughout the stem and leaves, are ingested by monarch larvae (caterpillar) when they eat the leaves which is the only food they eat until they transform to a pupa (chrysalis).  Their relationship offers a classic example of co-evolution, a process of adaptations when species interact. From the recently published book, Monarchs and Milkweed: “Most plants deploy multiple defensive traits that insects progressively overcome: Kill the herbivores, slow them down, deny them nutrients, call in their enemies, or just live with them” - milkweed does all of them! After researching and reading about milkweed, I am ‘blown away’ (a seed parachute pun) at what a remarkable plant it is.  

Monarch caterpillars are able to sequester the toxic glycosides, an adaptation passed through many generations of monarch evolution. Some caterpillars will succumb to milkweed's poison but for the most part monarchs have co-evolved with the milkweed plants, adjusting their ability to sequester the toxic chemical to the milkweed's ability to adjust its milky secretions. As a warning to potential predators about the presence of toxins, the beautifully striped caterpillar and the bright orange color of the butterfly are examples of aposematic coloration. Predators like birds often bite into a caterpillar or butterfly and quickly regurgitate the highly bitter flesh.

LET'S RAISE SOME BUTTERFLIES

I am deeply concerned about the declining populations of western monarchs so I have decided to rear monarchs next summer, making use of my expanding milkweed patch to support their growth and transformation. If you want to learn more about monarchs and how they use and need vast swaths of milkweed to survive their 3000 mile journeys,  I highly recommend reading the three books I list below.

But first you need a milkweed patch.

Monarchs and Milkweed: A Migrating Butterfly, A Poisonous Plant and Their Remarkable Story of Co-Evolution by Anurag Agrawal

Written by a researcher, the author does an admirable job of explaining both his research and methodology. The book offers a review of historical thinking and science around the monarch butterfly and its plant ally, milkweed.

Chasing Monarchs: Migrating with the Butterflies of Passage by Robert Michael Pyle

An ecologist heads out to explore the western locales for monarch butterflies.  A delight to read!

Flight Behavior: A Novel by Barbara Kingsolver

Many readers don't know that Kingsolver was first trained and educated as a biologist.  This novel contains many facts and explanations of research methods about monarchs but she also explores the human thinking around poverty, class and uses of natural resources. 

I will end this profile with a beautifully written excerpt from Pyle’s book, Chasing Monarchs, about the monarchs’ annual and generational return trip to their North American homes:

Females seeking milkweed, males seeking females, both seeking nectar, the monarchs fly north until they die along the way. Their wings, whose translucent tissues that have carried them two hundred or two thousand miles already, lose their scales and their color.  They grow tattered, torn, bush-ripped, bird-struck. The wings still work for flying, if not so fast, efficiently, or high. But a female no longer needs to fly high, to soar or glide great distances. Her only need now is to skip and hop and flutter from field to roadside, bush to herb, to palp the air and the green spring for the next scrap of milkweed on which to deposit her precious eggs. Day after day she drops her load until she has laid some five hundred eggs or more.  Or until a spring storm or an automobile or a recently molted mantis lays her to rest.  Or until, her abdomen grown greasy with the the thinness of its walls, her wings pale rags, she simply wears out.

A few monarchs may reach the state, the county, the meadow where they began, but this must be very rare.  The great mass of last fall’s emigrants scatter their last scales to the wind somewhere far short of their birthplaces.  It will be up to their offspring to carry on.  The eggs - fluted golden ovals - darken in a few days, then give forth comma-sized caterpillars. These consume milkweed flesh until they burst their skins, five times.  As they gnaw the host plant, they spill its latex, which will embitter their own tissues. In less than a month the caterpillars have grown as large as a child’s little finger.  After the fifth molt comes the jade jewelbox, the gold-nippled smooth green chrysalis. From this inch-long pellet will come a butterfly whose wings span three or four inches.  Once they break free of their confining chrysalides, then dry in full turgo, they are capable of rising, soaring, and gliding better than any kite. On the first morning breeze they take wing, rise on the thermals, level out, float and pump higher, higher, until, hundreds or perhaps  thousands of feet in the air, they begin the masterful glide that can carry them many miles. If the air is heavy, they move close to the earth.  And so from the millions of shimmering pupae, tucked beneath the leaves of milkweed from St. Augustine to Santa Barbara, will issue the next rush of the sky river, flowing north and east.  (pp.2-3)
 


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