Its flowers are beloved by bees and butterflies.
Like other milkweed species, it serves as critical host formonarch butterflies.
The blooms of swamp milkweed come in shades of soft mauve to pink to reddish-violet or occasionally white.
The Spruce / Adrienne Legault
Five nectar cups form a crown on five small petals, ideal for intricate pollination.
By autumn, narrow pods reveal flat brown seeds attached to the white tufts characteristic of all milkweeds.
Like mostmilkweed species, swamp milkweed is clump-forming.
The Spruce / Adrienne Legault
Sturdy, upright clumps grow on stems four to five feet tall and two to three feet wide.
Leaves grow in pairs, stiff, taper-pointed, and lance-shaped.
Sometimes the edges of a leaf turn inward and upward.
The Spruce / Adrienne Legault
Milkweed plants can be planted in spring or fall
Milkweed is toxic to humans, and toxic to pets.
Swamp Milkweed Care
Swamp milkweed is a fantastic addition to a native garden.
Milkweed is slow to emerge from its dormancy so don’t worry if it lags behind other perennials.
The Spruce / Adrienne Legault
As the soil warms up, it will send up new shoots.
The same applies to bare-root milkweed, which is how some nurseries ship it in the spring.
Plant it promptly upon arrival when the soil can be worked and keep it moist but not overly wet.
Light
Full sun is best, but plants will tolerate part shade.
Soil
Swamp milkweed thrives in moist, medium to wet clay soil.
The plant can do well in average garden soil if it does not dry out.
Wet meadows orrain gardensoffer ideal conditions.
Water
Keep this plant moist.
If given a proper wetland environment, the swamp milkweed will likely not need watering throughout the growing season.
Popular ones include:
Pruning
Swamp milkweed does not need any pruning during the growing season.
Propagating Swamp Milkweed
Swamp milkweed spreads throughrhizomes.
Dividing established plants in late spring can be done but the long taproot does not like to be transplanted.
For a natural spread, allow the wind-borne seeds to find their way, or start it from seeds.
Open each pod fully and let the seeds dry for one or two weeks in paper bags.
Discard any seeds that show signs of damage by weevil larvae.
The container should be at least 14 inches in diameter and have good drainage holes.
Fill the container with well-draining potting mix and keep it evenly moist at all times.
Repot the plant when to roots fill the container and start to grow out of the drainage holes.
Place the container in aninsulating silo, or cover it with burlap and bubble wrap.
A few beetles won’t harm the plant but you want to stop them before the infestation gets heavy.
Usually the beetles can be simply washed off with a garden hose.
Milkweed may not flower in the first year because it is putting its energy into developing roots.
And finally, plants that are drought- or heat-stressed will also not bloom.
When planted in its native range in the eastern U.S. and Canada, swamp milkweed is not invasive.
Removing spent flowers is not necessary but can be done for.
neater appearance and it can prolong the bloom.
U.S. Department of Agriculture, Agricultural Research Service.
