Got Milk…….. Weed?

Painted Lady butterfly on milkweed

Painted Lady butterfly on milkweed

One of the most beautiful flowers, both in flower and seed pod, as well as great importance to wildlife, has been relegated to the roadside for years and virtually ignored. Asclepias syriaca, or common milkweed, is struggling and harder to find because wild areas are disappearing and roadsides are  regularly mown. “Familiarity breeds contempt” is a common saying and one that I would apply to this plant. Only when something becomes scarce do we appreciate it, and I can see that happening with milkweed. But there is a sea change coming down the pike and people are being urged to plant this “weed”.

One colony of plants connected by underground roots

One colony of plants connected by underground roots

Acknowledged as a primary source for survival of many insects, notably the Monarch,  people are waking up to its integral role in supporting other wildlife. See my post Monarch Waystation on the many reasons to plant milkweed for Monarch survival.

Milkweed has a highly complex flower structure and quite beautiful

Milkweed has a highly complex flower structure and is quite beautiful

Milkweed Facts

  • Milkweed is the only plant on which monarch butterflies will lay their eggs, and it is the only food source for monarch caterpillars

  • It grows in colonies that expand in size every year; each individual in a colony is one side shoot of a large plant and are genetically identical or a clone; one large branching underground rhizome connects the entire colony

A caterpillar munching away at a milkweed leaf

A caterpillar munching away at a milkweed leaf

  • Surprisingly, the flowers are extremely fragrant and you can smell a colony long before you see it

  • Although one shoot may have between 300 to 500 flowers that make up the umbels, only a few of these develop into pods

    Pods of milkweed are held vertically

    Pods of milkweed are held vertically


  • Vegetative and flower growth is rapid, but the pod development is very slow and held on the plant for many weeks

  • All pods are held vertically to the plant and hold many seeds; germination of these seeds is very sparse; milkweed more likely expands by underground rhizomes than from seed

    Thorny pods of milkweed

    Thorny pods of milkweed

  • The nectar is very high in sugar content, 3% sucrose, and the supply is constantly being renewed over the life of the flower; the flowers produce much more concentrated nectar than the many insects that feed on it could ever remove

  • Milkweed teems with insect life, providing food and microhabitat to hundreds of insect varieties


  • At least 10 species of insects feed exclusively on milkweeds, notably the Monarch butterfly caterpillar

Monarch caterpillar

Monarch caterpillar

  • The adult Monarch lays its eggs on the leaves of common milkweed, the larvae live on its leaves and milky sap, and the adult Monarchs drink from the flower nectar, although adults will drink from other flowers

  • The latex milky sap from the milkweed is extremely toxic to other wildlife and is concentrated in the tissues of the Monarch which protects it against predators

The milky sap is toxic

The milky sap is toxic

  • The adult Monarch migrates south. East of the Mississippi, they fly as far as 4,800 meters to over winter in Mexico, often to the same tree location

    Tropical Milkweed, Asclepias curassavica, is found in hotter climates, like Florida

    Tropical Milkwwed, Asclepias curassavica, is found in hotter climates, like Florida

    This relationship between the milkweed plant and the monarch butterfly makes the pairing a symbiosis, where they become one entity instead of two separate organisms. Most importantly, without the presence of the milkweed plant, monarchs would go extinct.

Asclepias incarnata

Asclepias incarnata

Other Varieties of Milkweed

Asclepias tuberosa, orange-flowered Milkweed below is probably my all time favorite for drawing insects and pollinators to the garden early in the season, around June for me in the mid-Atlantic. A long-lasting cut flower, I scatter it through my borders to brighten up early summer plantings. It comes in an all yellow version called “Hellow Yellow”.

Yellow butterfly Weed "Hello Yellow"

Yellow butterfly Weed “Hello Yellow”

Another milkweed which is a conversation piece oddity is Asclepias physocarpa, or Hairy Balls. Forming puffy seed balls two to three inches in diameter, the orbs are covered with hairs and are quite bizarre looking. Perfect for flower arranging, the cut branches are quite expensive to buy from a florist, but easy to grow. A favored host of the Monarch butterfly, I always try to grow this plant for the odd looking pods.

Hairy balls forms a bizarre pod

Hairy balls forms a bizarre pod

Tropical milkweed, Asclepias curassavica, is commonly seen growing in Florida and has bright red-orange and yellow flowers and is also a great nectar source. The leaves are narrower and the plant produces many more seed pods than the common milkweed.


About thegardendiaries

Claire Jones is a landscape and floral designer and owner of Claire Jones Landscapes, LLC. She designs and helps people to create their own personal outdoor oasis and loves to write about her gardening failures and successes.
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17 Responses to Got Milk…….. Weed?

  1. Anne says:

    I love my milkweed! We see fewer and fewer monarchs around here, but the large milkweed presence in my garden (mostly common milkweed, but I’ve also planted butterfly weed, swamp milkweed, and (?) purple milkweed) has produced some Monarch presence. My neighbor and her children discover eggs and raise them for release – Monarch caterpillars coming soon!

    So exciting to be part of saving this endangered, beautiful butterfly.

    Liked by 1 person

  2. Linda T says:

    Beautiful blog on the milk weed. The larger pictures and video are great!
    Thanks Claire.


  3. Rose says:

    Asclepsias physocarpa is a new plant to me–very interesting, though I’d definitely have to remember its botanical name to avoid lots of snickers from my older grandchildren:) Living in the heart of farm country here, I can explain part of the demise of common milkweed. It’s a real nuisance in corn and soybean fields, so it’s fallen victim to chemicals in the past 20-30 years. But I’m happy to report that I see more and more of it along the rural roadsides and even in plantings along the interstate. The ironic thing is that so far I haven’t had any luck getting the common milkweed to grow in my garden!


  4. I keep looking for it but haven’t found it here. Maybe I wouldn’t recognize it if I saw it. How does one contain the invasive roots?


  5. Julia says:

    ‘Hairy Balls’ is called Gomphocarpus physocarpus (Asclepias physocarpa). We have one in our garden from Telly’s Greenhouse is Troy, MI. I didn’t realize the Monarchs liked them~great news! Terrifically informative and beautiful blogpost. Thank you!!!


  6. What a great post–valuable information and identification of plants!


  7. Of Gardens says:

    I am cultivating a bed of Common Milkweed – the bed spontaneously appeared and I decided to nourish it in the hope some Monarchs will breed in my garden.


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