When staying at the cabin during the summer I love to spend time in the 40-acre mountain-top field surrounded by extensive mixed forest.  I may be working, walking or just sitting. Nearly 2,000 feet in elevation on the northern edge of the Appalachians in central New York State, it is a cold, windy place in winter. At the hands of the former owner, the acreage was an overworked and undervalued hayfield with limited care and feeding. These days, in mid to late summer the field is alive with creatures of all sorts going about the business of life.

Over the last 22 years we have planted over 80 species of trees and shrubs on the old farm (over 3,500 plants in total) with the goal of diversifying the plant community. In this manner, we have significantly increased the wildlife carrying capacity of the land with new sources of food and shelter. Combined with 10 small ponds and potholes created around the property, the land has flourished as wildlife species take advantage of this bounty.

While it is always rewarding to spot white-tailed deer, wild turkeys, rabbits or foxes, I also enjoy watching the dozens of species grouped together as pollinators. These number in the thousands, ranging from ants, wasps, flies, moths and beetles to butterflies, birds, bats and field mice. Attracted by the colors, scents and tastes of flowering plants, pollinators work overtime gathering nectar, plant matter and insects for food.

As they move among flowering plants, pollinators collect pollen on their bodies and then distribute that pollen among other plants in the field. In doing so they play a critical role in the complicated food web that sustains all life on Earth. Scientists estimate that up to 70 percent of the foods consumed by humans are produced, at least in part, through the miracle of pollination.

There is a family of plants that play a special role in the pollination drama, the milkweeds. For many of us, the sight of common milkweed blooming in a roadside ditch is a sign of high summer. The heavy, spherical clusters of light pink flowers emit a pleasant fragrance you may detect from yards away. For the monarch butterfly, this plant is far more than a source of perfume; it is an absolute biological necessity. As we navigate a changing climate and shifting biodiversity, understanding the diverse varieties of milkweed (Asclepias) in the Pine Tree State is essential for anyone looking to support our local pollinators.

Milkweed was named for the thick, white latex sap that oozes from the stem or leaves when broken. This sap contains cardiac glycosides, special compounds that are toxic to most vertebrates including humans. While these chemicals serve as a defense mechanism for the plant, they are also the secret weapon of the monarch butterfly (Danaus plexippus). Monarch caterpillars are highly specialized feeders on milkweed leaves; they have evolved to tolerate these toxins, sequestering them in their own bodies to make themselves unpalatable to birds and other predators. Without the ability to lay their eggs on the undersides of milkweed leaves, the monarch’s lifecycle cannot continue.

However, the benefits of milkweed extend well beyond a single butterfly species. The complex physical structure of the milkweed flower—featuring a “horn” and “hood” assembly—requires insects to slip their legs into narrow slits to reach the nectar. When the insects withdraw their legs, they often carry a sticky sac of pollen, called a pollinium, to the next flower. The milkweed plant serves as a high-value nectar source for honeybees, bumblebees, and predatory wasps that help to control garden pests such as aphids.

Among more than 100 species of milkweed in North America, Maine is home to several distinct varieties, each adapted to different niches in our landscape. Common milkweed (Asclepias syriaca) might be called the “workhorse” of the genus and it is the variety most people recognize. It is a robust perennial, three to five feet tall with broad, velvety leaves. It spreads aggressively via underground rhizomes, what you might call a network of horizontal roots that send up new shoots to allow the plant to expand its territory.  This makes common milkweed well suited for large meadows but too assertive for a small garden. It is quite resilient, handling diverse conditions such as salt spray in coastal Harpswell and heavy frosts in the North Woods.

Swamp milkweed (Asclepias incarnata) unlike its common relative, grows in clumps and does not spread through rhizomes. This variety is therefore easier to manage in a backyard setting or formal pollinator garden where you like to keep individual plantings distinct and separate. Swamp milkweed produces lush, deep-pink to mauve flowers and prefers moist soils found near ponds, streams, or in low-lying areas of our yard. Worth noting is that this plant is favored by the spectacular great spangled fritillary and various swallowtail butterflies.

Butterfly weed (Asclepias tuberosa) is unique among Maine’s milkweeds, producing brilliant orange flowers and lacking that milky sap. It is shorter than other varieties, around two feet, and prospers in well-drained, sandy soils found along Maine’s coastline. It is also drought-tolerant and really pulls in the pollinators thanks to those neon-orange clusters that are visible from a great distance.

As I described in an article about the monarch butterfly in December 2020, butterflies are facing a critical loss of milkweed plants across the country.  Over the last four decades, many insects including the monarch have suffered huge declines (40 percent or more) due to habitat loss and the widespread use of herbicides that eliminate milkweed from agricultural “fringe” lands. Products like Roundup (glyphosate), 2,4-D, Triclopyr and Dicamba are non-selective herbicides, used by farmers to wipe out nearly every green plant from their fields except the desired crop, for instance corn or soybeans. The problem is that the herbicides can drift on any breeze and kill plants beyond the field’s borders. (I could write an entire article about the impact of these products on riverine systems, groundwater and human health!). Maine and other states are finally taking steps to tighten regulations on the use of these herbicides and pressuring the EPA and USDA to require more testing before licensing replacement products.

In recent years many conservation groups both local and national have launched programs encouraging the general public to plant milkweed in gardens, dormant fields and even in the medians of national highways to support migrating butterflies. In Maine, we are seeing more enthusiasm for a movement referred to as the “Homegrown National Park” concept—the idea that private yards across the country can serve as a fragmented but vital corridor for migrating species. By removing invasive plants and planting a mix of native common, swamp, and butterfly milkweeds, Maine gardeners can beautify their land while giving pollinators an important helping hand.

To introduce milkweed on your land, late summer and autumn are the ideal times to plan. Milkweed seeds need cold stratification—a period of cold, moist conditions—to germinate. In Maine, this happens naturally if you introduce the seeds in the fall.

When the seed pods (follicles) of existing plants turn brown and split open, revealing the lovely white silk attached to the tiny seeds, they are ready for dispersal. Mother Nature does this with the wind but you can gather seeds and simply press the seeds into the soil surface in a sunny spot. Please make certain that you are planting native Maine varieties rather than imported tropical milkweeds since they may carry parasites and disrupt migration timing for the butterflies.

After too many years of ignorance about the importance of plants like the milkweeds and the creatures who seek out their blooms, scientists and the public are finally gaining much better understanding of the native cycle of life and how we can promote, rather than destroy it.  Milkweed plants are an important part of the complexity of the Maine ecosystem. Welcoming beautiful monarch butterflies and other less famous insects to Harpswell each summer, we are reminded that the simple act of planting—choosing a native Asclepias over a sterile ornamental—is a step each of us can take to improve the environment around us. Books or articles from scientists and authors like the brilliant Dr. Doug Tallamy, a professor of Entomology and Wildlife Ecology at the University of Delaware, should be on your reading list.

N.B. In closing, a note on safe handling of milkweed plants. If you have the need to handle mature plants, either the stems or the leaves, it is recommended that you wear gloves to avoid ingestion of the plant and any contact of sap with your eyes. Even contact of the plant with the skin can cause a reaction in some humans.

If you like Ed Robinson’s writing, check out his two Nature Notes books! Click here for more information.