6 Types of Milkweed in Manitoba (AND One to Avoid!)
“What types of milkweed should I plant in my garden?”
This may seem like a crazy question if you’re just getting started with native gardening. Why would you want to plant a weed?!
But milkweed isn’t a weed at all. Instead, it’s a flowering plant that attracts butterflies (think Monarchs), native bees, and other pollinating insects, which is an excellent thing!
This article will give you information about common types of milkweed in your area and which ones will be best for your garden. And, keep reading to the end to learn about a kind of milkweed you want to avoid!
6 Types of Milkweed in Manitoba:
#1. Common Milkweed
- Asclepias syriaca
Growing Information:
- USDA Hardiness Zone: 3-9
- Life Cycle: Perennial
- Approximate Mature Size: 1 to 1.5 meters; up to 2.5 meters.
- Bloom Time: June to August
Common Milkweed is the species most people think of when they hear the name milkweed. It’s a hardy perennial and one of the most common types of milkweed in Manitoba.
Milkweed gets its name from the latex or milky white secretions produced if the stem or leaves are broken. The leaves are oval, about 15 to 20 centimeters long, and dark green.
The blooms of the Common Milkweed plant are clusters of tiny flowers on stems that radiate from the larger central stem. These clusters are called umbels. The fragrant flowers are greenish-pink, pink, or purple and give way to 10-centimeter seed pods in the late summer and early fall. Initially, the pods are green but slowly mature to brown. Eventually, they split open, revealing seeds and fluffy white material called coma that allows the seeds to disperse on the wind.
Common Milkweed is an incredibly important wildflower in Manitoba.
Over 450 native insects feed on the nectar, sap, leaves, and flowers. In addition, it’s an important food source for caterpillars of the Monarch Butterfly (Danuas plexippus). The adult butterflies lay their eggs exclusively on members of the milkweed (Asclepias) family.
Interestingly, all milkweed species contain cardiac glycoside compounds. Monarch Butterflies and other insects consume milkweed and store the compounds in their bodies. Potential predators have learned to steer clear of Monarchs to avoid this dangerous and bitter poison!
Common Milkweed is relatively easy to grow, and it’s one of the easiest ways you can help support Monarch Butterflies. You’ll need a place that receives full sun for planting. Common Milkweed does best in well-drained areas but isn’t picky about soil and can be grown in clay, loamy, or sandy areas. They tolerate poor soils and don’t need to be fertilized. It’s essential never to use pesticides on these plants since they kill species like Monarch Butterflies.
Common Milkweed can spread by seed, or underground rhizomes, which are root colonies. This means you can add Common Milkweed to your garden by directly sowing seeds or planting cuttings from an existing plant.
#2. Whorled Milkweed
- Asclepias verticillata
Growing Information:
- USDA Hardiness Zone: 3-10
- Life Cycle: Perennial
- Approximate Mature Size: 30 to 90 centimeters
- Bloom Time: May to September
Whorled Milkweed is the most broadly distributed milkweed species in Manitoba.
This unique perennial is sometimes overlooked by gardeners who want to plant milkweed. Compared to other varieties, it has a narrow stem and spiky leaves arranged in a spiral pattern. When not in bloom, it easily blends in among grasses.
It blooms from May to September, forming flat-topped clusters of small greenish-white flowers on the end of each stem. The flowers attract various insects, including bees, wasps, butterflies, skippers, beetles, and flies.
Whorled Milkweed is still a welcome host plant for Monarch Butterfly caterpillars despite its unique appearance. Since this species is one of the last milkweeds to die back in the fall, it’s a great late-season host for Monarchs preparing to migrate south!
This delicate-looking wildflower can easily grow from seed, but it may not flower the first year. It can be grown in full sun or partial shade. Whorled Milkweed thrives in various habitats, including fields, pastures, roadsides, dry prairies, dry slopes, woodlands, and meadows. Unfortunately, it’s highly poisonous to livestock and is considered a nuisance weed in agricultural areas.
It grows best in dry soil of various types, including sandy, rocky, and clay soils. It can also be grown in moist, average garden soil. Keep in mind that it is an aggressive spreader by seeds and underground rhizomes, so you may not want to choose this milkweed if you have a limited area for gardening.
#3. Green Comet Milkweed
- Asclepias viridiflora
Growing Information:
- USDA Hardiness Zone: 3-10
- Life Cycle: Perennial
- Approximate Mature Size: 45 to 60 centimeters
- Bloom Time: June to September
Green Comet Milkweed flower clusters form in the pocket created by the upper leaves. They’re made up of 20 to 80 small, pale green flowers. Interestingly, the yellowish-green leaves of this species vary in shape depending upon their habitat. Plants from moist sites tend to have rounder leaves, while plants from dry sites have long, narrow leaves.
In the wild, this species is often found on shaded roadsides, savannas, and prairies with moist to dry soil. In the garden, you can grow Green Comet Milkweed from seeds. It grows best in light to moderate shade but will tolerate full sun. Medium-dry to dry soil is best. Green Comet Milkweed doesn’t need rich soil and will tolerate sandy or rocky soil with low organic matter.
This species is a good choice for low-maintenance gardens as its long taproot allows it to tolerate drought well. Unlike many other milkweeds, this species is easy to prevent from spreading. It doesn’t form the large colonies typical to other milkweeds, so it’s an excellent option for smaller gardens!
The Green Comet Milkweed’s copious nectar and sweet fragrance attract many pollinators, including honeybees, native bees, and butterflies. It’s also a host plant for Monarch Butterflies, though it can be more challenging for monarchs to find because of its scarcity and preference for partial shade.
#4. Showy Milkweed
- Asclepias speciosa
Growing Information:
- USDA Hardiness Zone: 3-8
- Life Cycle: Perennial
- Approximate Mature Size: 145 to 90 centimeters; occasionally up to 3 meters
- Bloom Time: May to September
As the name suggests, Showy Milkweed features flashy pink and white umbels or clusters of small flowers. The flowers are fragrant, and individual flowers look a bit like crowns. In ideal conditions, Showy Milkweed may grow as tall as 3 meters!
As a garden plant, Showy Milkweed has the benefit of being a less aggressive spreader than most other milkweed varieties in Manitoba. It can be grown easily from seed or the cuttings of an existing plant. It’s very drought tolerant and can be grown in a wide range of soils.
Like other milkweeds, Showy Milkweed attracts native insects and Monarch Butterflies to your yard or garden. Monarchs will visit the flowers for nectar and lay eggs on the plants, which are host plants for the Monarch caterpillars. It will also attract beautiful Queen and Viceroy butterflies to your property!
#5. Swamp Milkweed
- Asclepias incarnata
Growing Information:
- USDA Hardiness Zone: 3-6
- Life Cycle: Perennial
- Approximate Mature Size: 1 to 1.5 meters
- Bloom Time: June to October
As the name suggests, this moisture-loving perennial is typically found growing wild on creek banks and ditches or in openings in swamps, bogs, marshes, and other wet areas. So if you’re looking for a plant for the wet spot in your yard, Swamp Milkweed is a perfect choice.
This species thrives in wet, mucky clay soils. It’s great for planting around ponds or streams on your property. This species requires full sun to thrive.
Like other milkweeds in Manitoba, the blooms are clusters of smaller flowers. The light pink, purple, or white flowers of Swamp Milkweed will attract various species of native bees and butterflies to your garden. It’s also a host plant for monarch butterfly caterpillars.
RELATED: 19 Rabbit Resistant Plants to grow in Manitoba!
#6. Oval-leaved
- Asclepias ovalifolia
This lesser-known milkweed plant can be tricky to spot in Manitoba! The slender, unbranched stems do not grow very tall, making them blend in with the surrounding plants. Look for it growing in dry soil in prairies, savannas, dry riparian terraces, and open pine woodlands.
As the name suggests, Oval-leaved Milkweed has opposite, oval-shaped leaves that are a little broader at the base and narrow to the tip.
Oval-leaved Milkweeds usually flower between May and July. Typically, the flowers are white with some pale green or pinkish-purple tones and often fade to yellow with age.
The flowers give way to narrow, spindle-shaped pods. These erect pods mature to brown and split open along one side to release brown seeds with silky pappuses that are spread by the wind.
Tropical Milkweed
- Asclepias curassavica
Growing Information:
- USDA Hardiness Zone: 8-11
- Life Cycle: Perennial
- Approximate Mature Size: up to 1.5 meters
- Bloom Time: March to November in temperate climates, year-round in tropical climates.
This non-native milkweed plant has become popular in recent years because of its flowers’ bright red coloring and how easy it is to plant and maintain.
Unfortunately, Tropical Milkweed planted in Manitoba may do more harm than good.
It carries a parasite of Monarch Butterflies called Ophryocystis elektroscirrha, or OE, which can cause defects in the wings of Monarchs. Since it doesn’t die back and can bloom late, the plant itself may also confuse Monarchs by signaling a breeding season when it’s time to migrate.
To ensure you’re planting milkweed that will help your local ecosystem and attract native pollinators, always choose a native species!
Marketers of Tropical Milkweed seeds will use the names Mexican Milkweed, Bloodflower, Mexican Butterfly Weed, Mexican Orange Milkweed, and Semi-Tropical Milkweed. Steer clear of all of these!
Are you looking for more information on milkweed in Manitoba?
Check out this guide!
Do you have milkweed in your garden?
What’s your favorite thing about this plant? Leave a comment below!
