Milkweeds Aren’t Really Weeds

I am always confounded as to why plants that are top pollinator plants in our ecosystems are called weeds. Joe-Pye Weed (Eutrochium spp.) and Sneezeweed (Helenium autumnale) are two examples. I prefer the name Helen’s Flower for Sneezeweed. This plant, once used by some Native peoples as a snuff, doesn’t cause allergies at all. Weeds are usually defined as unwanted plants growing in a certain location. Maybe these plants encroached on farmers’ forage fields and were not palatable to livestock. Perhaps if our local Common Milkweed (Asclepias syriaca) was called “Monarch Butterfly Flower” it would get less of a bad rap.

Now, with the news of world pollinator declines and the movement to improve backyard and community biodiversity, milkweeds are all the rage. They should be, for not only are these plants among the top pollinator nectar plants for all kinds of native bees and butterflies, milkweeds are the only larval food plant for the Monarch Butterfly (Danaus plexippus). Monarch Butterfly caterpillars butterfly feed only on the leaves of milkweeds. The caterpillar will crawl up the stem and bite the plant’s midrib to cut off the flow of milky, sticky sap, and then move to the outer edge of the leaf to begin feeding. They do ingest some of this milky substance, which contains a heart poison (a cardiac glycoside). This sap deters many other insects, but the Monarch has evolved with this plant and is not harmed by it. In fact, the chemical makes the butterflies toxic to birds and other predators.

Three milkweed species are most common in our area: Common Milkweed (Asclepias syriaca), Swamp Milkweed (Asclepias incarnata), and Butterfly Weed (Asclepias tuberosa). Common Milkweed spreads by rhizomes, so the plant tends to roam. You will need a bit space to let it do so. I let the grass grow in a section of my lawn, but the milkweed has decided to pop up in another area. Oh well. I’ll just leave it for the Monarchs and gradually get rid of more lawn.

In many places of the country Common Milkweed is not so common anymore, particularly with increased planting of glyphosate-ready crops as well as roadside invasive plants taking over. When was the last time you saw milkweed in your neighborhood?

Butterfly Weed and Swamp Milkweed are both clumping species and would be fine in a pot outside your apartment or planted in your garden. Butterfly Weed can take dry soils once established, but is very adaptable.

Swamp Milkweed, as its name implies, likes moist soil, but it is also adaptable to regular garden soils. All three milkweeds will thrive in full sun, but will also do well in part-sun spots.

Monarch butterflies, like other pollinators, are better able to see and find a grouping of plants rather than an individual milkweed hidden within lots of other plants. A study at the University of Kentucky found that planting milkweeds in clumps out in the open or at the edge of a garden bed attracted more caterpillars than plants within a bed. It also showed how important our urban gardens are to pollinator conservation.

Here in Connecticut, there are several generations, or broods, of Monarchs. The final generation is the “Methuselah” brood. Monarchs that hatch, or eclose, in this final brood in September will migrate 2,800 miles to a mountaintop oyamel fir forest in Mexico’s Monarch Biosphere Reserve! These butterflies have never been there. Scientists think they use Earth’s magnetic field and the sun’s position to guide them.

Many families like to raise Monarchs by seeing them through their life stages from egg to larva to pupa to chrysalis, and then releasing the adults. But research has shown that raising these butterflies indoors can cause them to not migrate successfully. Monarchs that are raised outdoors and purchased locally, rather than from elsewhere, are better able to migrate.

We can all help pollinators like the Monarch. Whether on an apartment stoop, in a garden, or at nearby open lot—plant it and they will come.