Milkweed Species in Southern Ontario

📝📸 John Lowry

In Southern Ontario, from early spring through the fall season, there is a virtual parade of various wildflowers to delight our senses, both visual and olfactory. Beginning in mid-June through July and sometimes into August, we see the appearance of members of the Asclepias genus, more popularly known as milkweeds.

Southern Ontario hosts (depending on which source you consult) from seven to ten different native milkweeds. Some are very common, for example Common Milkweed (Asclepias syriaca) and Swamp Milkweed (Asclepias incarnata), while others are less common such as Butterfly Milkweed (Asclepias tuberosa). In addition, there are species that are considered provincially rare such as the Four-leaved Milkweed (Asclepias quadrifolia) and Poke Milkweed (Asclepias exaltata).

Common Milkweed

Swamp Milkweed

The milkweeds play an important role in supporting some of our more iconic pollinators, the Monarch (Danaus plexippus) being a case in point. Common Milkweed (as well as several of the other milkweeds) play host to Monarch caterpillars during the summer before they morph into butterflies and begin their epic journey to their overwintering grounds in the mountains of Mexico.

Of the more common milkweeds, there are plenty of examples to be observed across the region growing both in natural wild habitat as well as purposely planted in garden settings. The latter is often the result of a cross continent concerted effort to encourage gardeners to propagate this colourful plant and provide a food source and habitat for Monarchs. Monarch populations have exhibited a worrying decline in numbers in recent times.

Butterfly Milkweed

In the Quinte Region we are fortunate to host populations of several of the less common milkweed species. For instance, pockets of Poke Milkweed can be found in the Oak Hills to the northwest of Belleville. Further south, the County has several isolated populations of the Four-leaved Milkweed.

Poke Milkweed

Four-leaved Milkweed

Indeed, the County’s iconic ‘South Shore’ reportedly was home to some Four-leaved Milkweed at one time and hopefully some day we will be able to report that it continues to exist there and is only waiting to be re-discovered.