Common Milkweed
Latin Name: Asclepias syriaca
Identifying Characteristics:
- Has sticky milky sap
- Oval leaves, 4-9 inches long
- Leaves have very fine hairs on bottom side
- Flowers are arranged in an umbel with colors including pink, purple, orange, and white
- Generally, 3 ft tall or less
- Alternating veins coming off of leaf midrib
- Underground rhizomes (horizontal stems)
Plant Longevity:
- Perennial
Where Commonly Found:
- Fence rows
- Roadsides
- Fields
- Prairies
- Pastures
- Pollinator plantings
Time of Most Concern:
- When plant is green or dried in hay
Compound that Causes Concern:
- Galitoxin found in the sap
- Several glycosides
- Western species of milkweed, namely labrifom, whorled, and broadleaf milkweed, have higher concentrations of cardiac glycosides, whereas common milkweed lacks significant amounts of toxic cardiac glycosides
- Alkaloids
Part of Plant Most Toxic:
- Stems
- Leaves
- Roots
Livestock Species Affected:
- Cattle
- Goats
- Sheep
- Horses
- Poultry
Pasture, Stored Feed, Both:
- Both
Clinical Signs:
- Irregular pulse
- Vomiting
- Diarrhea
- Trouble breathing
- Loss of coordination
Amount Needed to be Consumed for Clinical Signs / Death:
- Studies have found that cattle can graze low amounts of milkweed with no effect, reducing need to strict control of this important plant to native pollinators.
- Toxic dose almost same as lethal dose
- As little as 2% of animal's body weight
- That would equate to 20 lbs in a 1,000 lb cow
- Frost decreases toxicity
Identifying Characteristics:
- Has sticky milky sap
- Oval leaves, 4-9 inches long
- Leaves have very fine hairs on bottom side
- Flowers are arranged in an umbel with colors including pink, purple, orange, and white
- Generally, 3 ft tall or less
- Alternating veins coming off of leaf midrib
- Underground rhizomes (horizontal stems)
Plant Longevity:
- Perennial
Where Commonly Found:
- Fence rows
- Roadsides
- Fields
- Prairies
- Pastures
- Pollinator plantings
Time of Most Concern:
- When plant is green or dried in hay
Compound that Causes Concern:
- Galitoxin found in the sap
- Several glycosides
- Western species of milkweed, namely labrifom, whorled, and broadleaf milkweed, have higher concentrations of cardiac glycosides, whereas common milkweed lacks significant amounts of toxic cardiac glycosides
- Alkaloids
Part of Plant Most Toxic:
- Stems
- Leaves
- Roots
Livestock Species Affected:
- Cattle
- Goats
- Sheep
- Horses
- Poultry
Pasture, Stored Feed, Both:
- Both
Clinical Signs:
- Irregular pulse
- Vomiting
- Diarrhea
- Trouble breathing
- Loss of coordination
Amount Needed to be Consumed for Clinical Signs / Death:
- Studies have found that cattle can graze low amounts of milkweed with no effect, reducing need to strict control of this important plant to native pollinators.
- Toxic dose almost same as lethal dose
- As little as 2% of animal's body weight
- That would equate to 20 lbs in a 1,000 lb cow
- Frost decreases toxicity
https://plants.usda.gov/DocumentLibrary/plantguide/pdf/cs_assy.pdf
https://hort.extension.wisc.edu/articles/milkweed-ornamental-plants-toxic-to-animals/
Dickson et al. Cattle graze central US milkweeds at least as much as grasses, even under patch-burn-grazing management. Rangeland Ecology and Management. 2023