CATHERINE RICHENS

PROFESSIONAL GARDENER

SPECIAL TO THE GAZETTE

Common Milkweed (Asclepias syriaca), named by Carl Linnaeus after the Greek god of healing and medicine, Asclepius, is now in bloom around the County. And that is exactly where it needs to be.

Native to North America and at home throughout Canada, in southern and central Ontario common milkweed is the host plant of monarch butterflies (Danaus plexippus). The sheer abundance of milkweed plants and the breeding habitat they create is paradise for the beloved butterfly. The leaves of this plant are the exclusive food source and birthplace for the monarch larvae and the caterpillar.

Monarch butterflies and milkweed share a special connection. (Illustration by Mabel Ray Richens)

Gently lift up and look on the underside of the milkweed leaves: the single, pinhead-sized white ball you may find there is the egg of the monarch butterfly.

Monarchs, along with 90 per cent of all plant-feeding insects, are specialists. That means they require a certain plant family or genus for their survival. The milkweed longhorn beetle (Tetraopes tetrophthalmus) is another example of an insect which feeds exclusively on a specific plant during its larval stage, in this case the roots of milkweed.

Monarchs and milkweed have an inextricable relationship. Without the common milkweed, there are no monarch butterflies. Monarch butterfly populations are on the decline. In 2022 migratory monarchs were added to the international list of threatened species, an indicator list that measures the health of the world’s biodiversity. In 2016 it was designated as endangered by the Committee on the Status of Endangered Wildlife in Canada.

Pulling out what we call “weeds” reduces vital insect populations. Weeding and ground- clearing create the conditions that contribute to the loss of key pollinators, reduce biodiversity, and put the health of humanity further at risk.

Milkweed, on the other hand, gives. It supplies these native insects with an abundance of nectar, and the supply is renewed over the life of the flower, giving them the much-needed fuel to survive.

Common milkweed is not so ordinary.

Milkweed supports the lifecycle of the Monarch, which travels 4000 km from Canada to Mexico for each fall migration — the longest migration of any insect species known to science. It has a complex and specialized flower structure, one second only to the Orchid, and it bleeds a poison that is both toxic and life-saving.

Named for the white milky sap exuded from its leaves and stem, milkweed protects the monarch from predators in all four of its life stages. The larvae and caterpillar ingest the sap and store it in their bodies. Because it is toxic to predators, the sap makes the caterpillars an undesirable food source, further evidence of the bond between the milkweed and the monarch.

Practicality aside, common milkweed imparts a heady, honey-like scent that is as much a part of summer as the heat. They are particularly beautiful towards the end of the season, when their seed pods ripen and split open, revealing layers of soft silky hairs attached to highly uniformed seeds that are gently coaxed out by the wind.

Milkweed is not just a plant (or a weed) — it does not exist on its own. It creates an exquisite bond and unfolding of events between two living things. The sap reminds of a mother’s milk, which nourishes and protects infants, making another kind of metamorphosis possible. It gives the Monarch the energy to span continents.

Catherine Richens is a professional ecologically-focused gardener living in Prince Edward County. [email protected]