Photo: Milkweed backgrounder

(Credit: Rick and Brenda Beerhorst via Flickr)

Here are some tips on how to grow milkweed, as well as information about the types of milkweed we recommend across Canada.

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Growing milkweed

Soil types

If you have a choice, light soils are better than those with heavy clay. Well-drained soils are generally best but Swamp milkweed do well in saturated conditions.

Where to plant

Most milkweed species evolved in open areas where they were exposed to full sunlight and they will do best if they are planted in the sunniest areas of your gardens.

Planting

Your seedlings should be planted at least six inches apart. Newly transplanted plants should be watered frequently. Add mulch around the seedlings soon after planting. The mulch holds in the moisture and minimizes the growth of competing weeds. To prevent spreading you may wish to add a border below the soil to separate milkweed from other parts of your garden.

Care and maintenance

The seedlings should be fertilized 2-3 times during the growing season if using water-soluble fertilizer or once a season if you utilize a granulated time-release formulation.

Preventing spreading

Common milkweed spreads both through seeds and rhizomes — underground lateral roots. To prevent spreading, you may wish to both add a below soil border and remove the seed pods before they open. Similar to dandelions, milkweed will spread to distant corners of your yard and beyond, thanks to the silky appendages that allow the seeds to waft on the slightest breeze.

Harvest and storage of milkweed seeds

The timing of the collection of milkweed pods or seeds is critical. If you squeeze the pods and they don't open easily, they usually do not contain mature brown seeds. Seeds well into the process of browning and hardening will germinate when planted the next season. Pale or white seeds should be not collected. Freshly collected pods should be dried in an open area with good air circulation. Once the pods are thoroughly dry, the seeds can be separated from the coma, or silk-like ballooning material, by hand. Store dried seeds in a cool, dry place protected from mice and insects — a plastic bag or other container in the refrigerator works well.

Milkweed types in Canada

Common milkweed (Asclepias syriaca)

Common-milkweed_BlueRidgeKitties.jpg Common milkweed (Photo credit: Flickr user BlueRidgeKitties)

Characteristics:
• Dense spherical umbels (flowers) at tip of stem and axils of upper leaves
• Flowers greenish to purple or white
• Pods, green, fleshy, covered with soft warty protuberences
Habitat: Pastures, meadows, roadsides
Range in Ontario: Common in southern and northern Ontario.
Native region in Canada: Manitoba, New Brunswick, Nova Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan
Find out more here.

Swamp milkweed (Asclepias incamata)

Swamp-milkweed_Danny-Barron.jpg Swamp milkweed (Photo credit: Danny Barron via Flickr)

Characteristics:
• Narrow-lanced shaped leaves, smooth
• Flowers dull pink to rose-purple
• Slender pods
• Smoothed stem
Habitat: swamps and wet meadows, ditches, edges of streams, shorelines
Range in Ontario: Throughout Great Lakes region of Ontario
Native region in Canada: Manitoba, New Brunswick, Nova Scotia, Ontario, Prince Edward Island, Quebec
Find out more here.

Butterfly-weed (Asclepias tuberosa)

Butterflyweed_Aaron-Carlson.jpg Butterfly-weed (Photo credit: Aaron Carlson via Flickr)

Characteristics:
• Distinct showy orange flower (sometimes yellow)
• Alternate leaves
• Leaves lanced shaped
• Juice not milky
• Narrow pods
Habitat: Sandy fields especially tall grass prairie and savanna communities.
Range in Ontario: Mostly Carolinian regions especially in sandy meadows
Native region in Canada: Ontario, Quebec
Find out more here.

Showy milkweed (Asclepias speciosa)

This species has flowers that resemble a cluster of brilliant pink stars. It does spread through underground rhizomes, but is not reported to be an aggressive spreader. It attracts both bees and butterflies. Find out more here.

Thumbnail image for Showy Milkweed -- Phillip Bouchard.jpg

Characteristics:
• Flowers: 4-5″ clusters of pinkish/purple fragrant blooms
• Large, thick leaves can sustain more caterpillars
• Monarchs use a nectar source and host plant
• Many other pollinators use as a nectar source
• Easy to start from milkweed seeds
• Long bloom period 2-3 months
Native region in Canada: British Columbia, Alberta, Saskatchewan, Manitoba
Find out more here.