Recognizing milkweed

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Where there are monarchs, there’s bound to be milkweed

Milkweed is a flowering plant essential to the life cycle of the monarch, as it is the sole source of food for the caterpillars. The survival of the butterfly depends on the accessibility of this host plant. An important part of Mission Monarch is to identify and map milkweed in Canada.

There are about a dozen species of milkweed in Canada, in nine of the ten provinces. Check out the identification sheets to find and recognize milkweed species in your area.


Swamp milkweed
Asclepias incarnata

Asclepias incarnata - photo by Patrick Alexander

SPECIFICATIONS
Stem: Downy (hairy), from 60 to 200 cm tall.
Umbels: Red or purplish-pink.
Leaves: Narrow, tapered, 4 to 17 cm long, arranged in opposite pairs.
Fruit: Long, narrow and smooth follicles, changing colour from green to brownish.
Habitat: Wetlands. Also found in swamps, ditches and near streams, rivers and lakes.
Populations:  Often scattered – does not form dense colonies.
Locations: Manitoba
Ontario
Quebec

Dwarf milkweed
Asclepias ovalifolia

Asclepias ovalifolia - photo by Justin Meisen

SPECIFICATIONS
Stem: simple (unbranched) and downy, 30 to 60 cm tall.
Flowers: greenish white or pale mauve corolla; orange or yellow corona.
Leaves: opposite, oval, with pointy tips, 5 to 8 cm long.
Habitat: likes sandy soil, roadsides and dry, sunny conditions.
Location:  British Columbia
Alberta
Saskatchewan
Manitoba
Ontario

Showy milkweed
Asclepias speciosa

Asclepias speciosa - photo by Matt Lavin

SPECIFICATIONS
Stem: 45 to 200 cm tall, velvety or pubescent (hairy).
Flowers: pale pink, arranged in umbels. The corona hoods are long (9 to 13 mm) and lance-shaped, making the flowers look like stars.
Leaves: opposite, 10 to 25 cm long, smooth or slightly downy.
Habitat: well-drained soil, sunny sites, pastures, swamps, forest edges, untilled fields, roadsides, ditches.
Location:  British Columbia
Alberta
Saskatchewan
Manitoba

Common milkweed
Asclepias syriaca

Asclepias syriaca - Sonya Charest

SPECIFICATIONS
Stem: downy, usually single, 90 to 120 cm tall. Underground stems.
Leaves: broad and thick, 10 to 20 cm long, arranged in opposite pairs on the stem and with pubescent undersides.
Flowers: pale pink or mauve, arranged in almost spherical umbels.
Fruit: large spindle-shaped fruit, bumpy, rough and downy.
Habitat: poor, dry soil, disturbed, sunny sites.
Location:  Saskatchewan
Manitoba
Ontario
Quebec
New Brunswick
Nova-Scotia
Prince-Edward-Island

Butterfly milkweed
Asclepias tuberosa

Asclepias tuberosa - photo by Aaron Carlson

SPECIFICATIONS
Stem: 20 to 60 cm tall.
Flowers: bright orange-yellow, arranged in umbels.
Leaves: alternate on the stem (not opposite each other), lance-shaped, 5 to 10 cm long, smooth on top and downy beneath.
Habitat: limestone soils, open, rocky, dry sites. Does not tolerate shade.
Unique feature: no milky sap.
Location:  Ontario
Quebec

Whorled milkweed
Asclepias verticillata

Asclepias verticillata - photo by Aaron Carlson

SPECIFICATIONS
Stem: angled, pubescent (hairy) or glabrous, 40 to 100 cm tall.
Flowers: white corona and greenish corolla.
Leaves: elongated and narrow, almost threadlike, 5 to 10 cm long. Arranged in groups of 2 to 4, opposite each other on the stem.
Fruit: elongated and lance-shaped, 7 to 10 cm long, glabrous or pubescent (hairy).
Habitat: dry, infertile soils.
Location:  Saskatchewan
Manitoba
Ontario

Green milkweed
Asclepias viridiflora

Asclepias viridiflora

SPECIFICATIONS
Stem: 30 to 90 cm tall, pubescent, green and sometimes purplish.
Flowers: arranged in often downward-facing umbels, pale green sometimes tinged with violet. Unlike other milkweed species, the flowers of this species have no corona hoods.
Leaves: arranged in opposite pairs on the stem. Vary in shape depending on the habitat where the plant is found. They may be long and narrow or broader and oval. The leaf edges may sometimes be wavy.
Habitat: dry, sandy or rocky soils, but also in wetter sites like marshes.
Location:  British Columbia
Alberta
Saskatchewan
Manitoba
Ontario