COMPARISONS

Here are some comparisons between Swamp Milkweed, Butterfly Milkweed and Common Milkweed. All photos by Denise Motard unless otherwise noted.

PLANT HEIGHT AND SHAPE
THE FLOWERS
THE LEAVES
THE PODS AND SEEDS
THE ROOT SYSTEM
TOXICITY

PLANT HEIGHT AND SHAPE:

Swamp Milkweed can reach a height of around 150 cm (5 ft.), whereas Butterfly Milkweed is shorter, up to one meter (3 ft.) high. Swamp Milkweed stems grow from a clump that gets larger every year, and those stems open up fan-like. Butterfly Milkweed stems are vertical and there may be a few emerging from one single root. Common Milkweed can reach heights of 2.6 meters (8 ft.), and the stems grow straight up from rhizomes.

Swamp Milkweed grows from a clump at the base and opens up fan-like.
Swamp Milkweed grows from a clump at the base and opens up fan-like.
This Butterfly Milkweed patch contains several individual plants growing vertically, not fan-like.
This Butterfly Milkweed patch contains several individual plants growing vertically, not fan-like.
Swamp milkweed clump with seed pods - Sept. 29, 2018
Swamp milkweed clump that started from one plant – Sept. 29, 2018
Common Milkweed is higher and has larger leaves than Swamp & Butterfly Milkweeds - photo by Derek Ramsay, 2007
Common Milkweed is higher and has larger leaves than Swamp and Butterfly Milkweeds – photo by Derek Ramsay – 2007
Butterfly Milkweed is shorter than Swamp Milkweed and the stems grow vertically, not fan-like.
Butterfly Milkweed is shorter than Swamp Milkweed and the stems grow vertically, not fan-like.

BACK TO THE TOP

THE FLOWERS:

Swamp Milkweed flowers appear as clusters at the top of the stems. They are usually pink, sometimes white. Butterfly Milkweed flowers also appear as clusters at the top of the stems, but the clusters are flatter. The blooms are usually orange, sometimes yellow. Common Milkweed flowers bloom alongside near the top of the stems, as pink clusters.

Swamp Milkweed blooms in pink clusters at the top of the stems - July 30, 2017
Swamp Milkweed blooms in pink clusters at the top of the stems – July 30, 2017
Butterfly Milkweed flowers close up - Aug. 10, 2018
Butterfly Milkweed flowers close up – Aug. 10, 2018
Common Milkweed flowers bloom in clusters, are pink and are positioned along the top of the stems, NOT at the top like Swamp & Butterfly Milkweeds. Photo by James Steakley.
Common Milkweed flowers bloom in clusters, are pink and are positioned along the top of the stems, NOT at the top like Swamp & Butterfly Milkweeds. Photo by James Steakley
Close up of white Swamp Milkweed blooms with a pollinator on them - July 25, 2014
Close up of white Swamp Milkweed blooms with a pollinator on them – July 25, 2014
Butterfly Milkweed blooms with a 3-pointed star shape - Aug. 10, 2018
Butterfly Milkweed blooms with a 3-pointed star shape – Aug. 10, 2018
Butterfly Milkweed blooms in clusters at the top of the stems. July 25, 2014
Butterfly Milkweed blooms in clusters at the top of the stems. July 25, 2014
Butterfly Milkweed sometimes displays yellow blooms in addition to orange ones - Aug. 8, 2015
Butterfly Milkweed sometimes displays yellow blooms in addition to orange ones – Aug. 8, 2015

BACK TO THE TOP

THE LEAVES:

Swamp and Butterfly milkweeds have narrow and pointed leaves. Butterfly Milkweed leaves are slightly smaller and darker than Swamp Milkweed leaves, and are hairy while Swamp Milkweed leaves are glabrous. Common Milkweed leaves are longer and larger, and their tip is more round. The vein system of the three species is also different.

Butterfly & Swamp milkweed leaves - Oct. 4, 2018 - Stratford, PEI
Butterfly & Swamp milkweed leaves – Oct. 4, 2018 – Stratford, PEI
Common Milkweed leaves - Mount Lebanon, PE - photo by Cbaile19
Common Milkweed leaves – Mount Lebanon, PE – photo by Cbaile19

BACK TO THE TOP

THE PODS AND SEEDS:

Swamp Milkweed pods are mostly still green when their seeds are ripe. They contain roughly 65-70 seeds. Most of the pods ripen about a month before the Butterfly Milkweed ones, from the end of September on Prince Edward Island.
The Butterfly Milkweed pods are longer, purple and hairy, and they ripen from the end of October on PEI. The pods contain around 80-90 seeds.
Common Milkweed pods are more plump and light green when still unripe, with soft spikes.
The pods of those three species split longitudinally when their seeds are ripe, and each seed has a small parachute to facilitate its spread.
The seeds are similar in shape but the Swamp Milkweed seeds are lighter brown and larger than the Butterfly Milkweed seeds, however the parachutes of the latter have longer silks than the former.

Swamp Milkweed pods stay green even when their seeds are ripe. They are glabrous.
Swamp Milkweed pods stay green even when their seeds are ripe. They are glabrous.
Swamp Milkweed pods on the left, Butterfly Milkweed pods on the right.
Swamp Milkweed pods on the left, Butterfly Milkweed pods on the right.
Common Milkweed seeds with their silk parachutes - Nov. 5, 2007 - photo by Kingturtle
Common Milkweed seeds with their silk parachutes – Nov. 5, 2007 – photo by Kingturtle
Swamp Milkweed pods are ripe whereas the Butterfly Milkweed have another month to go.
Swamp Milkweed pods are ripe whereas the Butterfly Milkweed have another month to go.
Swamp Milkweed pod on the left, Butterfly Milkweed pod at right. Note the longer parachute of the Butterfly Milkweed seeds.
Swamp Milkweed pod on the left, Butterfly Milkweed pod at right. Note the longer parachute of the Butterfly Milkweed seeds.
Common Milkweed seed pods are more plump than those of Swamp & Butterfly Milkweeds, and have soft spikes. Photo by H.Zell.
Common Milkweed seed pods are more plump than those of Swamp and Butterfly Milkweeds, and have soft spikes. Photo by H.Zell.
Swamp Milkweed seeds on the left, Butterfly Milkweed seeds at right. Note the differences in color and size.
Swamp Milkweed seeds on the left, Butterfly Milkweed seeds at right. Note the differences in color and size.

BACK TO THE TOP

THE ROOT SYSTEM

Swamp Milkweed forms a clump of roots, which are white and fleshy. The future stems grow from buds at the base of the plant, so that one plant clump has many stems after a few years. This makes it easy to transplant even when the clump is large.
Butterfly Milkweed grows a tap root which can reach up to 60 cm long (2 ft.) The future stems grow from buds around the tap root near the top, but underground. The tap root makes this species difficult to transplant.
Common Milkweed grows horizontal rhizomes that can extend several feet (meters), and stem buds start along those rhizomes. Thus one single plant can cover a large space. (Link to Michelle Clay’s photos.)

Butterfly Milkweed plants on the left, Swamp Milkweed at right: mature stem, 2 year-old plant, and 1 year-old plant.
Butterfly Milkweed plants on the left, Swamp Milkweed at right: mature stem, 2 year-old plant, and 1 year-old plant.
Butterfly Milkweed stem branching starts underground, quite deep actually - Oct. 4, 2018
Butterfly Milkweed stem branching starts underground, quite deep actually – Oct. 4, 2018
One of the Butterfly Milkweed tap roots broke when digging it up. Swamp Milkweed forms a clump of white, fleshy roots.
One of the Butterfly Milkweed tap roots broke when digging it up. Swamp Milkweed forms a clump of white, fleshy roots.
Common Milkweed roots - photo by Michelle Clay, Franklin, MA - Aug. 7, 2010
Common Milkweed roots – photo by Michelle Clay, Franklin, MA – Aug. 7, 2010
Close up of Swamp Milkweed fleshy root system showing the future stem buds around the crown - Oct. 4, 2018
Close up of Swamp Milkweed fleshy root system showing the future stem buds around the crown – Oct. 4, 2018
Common Milkweed rhizomes with new stem buds - photo by Michelle Clay, Franklin, MA - Aug. 7, 2010
Common Milkweed rhizomes with new stem buds – photo by Michelle Clay, Franklin, MA – Aug. 7, 2010

BACK TO THE TOP

TOXICITY:

Not all milkweeds have the same level of toxic substances (cardiac glycosides), which are harmful to humans and also grazing animals and poultry. Those toxins are most present in the plant sap, a milky substance that gives the plant its name.

Here are the levels of toxicity of the three milkweed species described here:
Swamp Milkweed : high
Common Milkweed : moderate
Butterfly Milkweed: low
This information is drawn from the following source: https://monarchwatch.org/bring-back-the-monarchs/milkweed/milkweed-profiles/.

Many wild plants such as milkweed are eaten as part of a more natural diet, however precautions need to be taken in the food preparation. There is information available online and in books about how to prepare milkweed, on which species can be eaten, which part and at which stage. On the other hand, other online sources do NOT recommend eating any milkweed.

BACK TO THE TOP

A site about Gardens and Monarch Butterflies