Horseweed - Erigeron Canadensis

Horseweed gets its common name from terpene, a substance produced by the plant that irritates any mammals that touch it.

Farmers noticed that horses who had come in contact with Erigeron Canadensis developed minor rashes on the tips of their noses.

Some people are also susceptible to developing irritation or a rash when exposed to Erigeron Canadensis’ here.

While Horseweed is generally disliked today, it was considered helpful by aboriginal people in the Americas. Erigeron Canadensis Erigeron Canadensis was commonly used to treat bleeding problems, flesh wounds, ulcers, hemorrhoids, high blood pressure, tonsillitis, and help kidneys flush excess salt and fluids. Indigenous people and early colonials also used it

to treat many heart conditions.

Other names for Erigeron Canadensis include Canadian Horseweed and Mare’s Tail.

Horseweed Appearance

Horseweed is a flowering, summer annual that can from anywhere from six inches to ten feet tall.

The central stem is solid and stout and covered in spreading white hairs. It is unbranched until the apex, at which point there are branched stems that produce flowers.

When immature, Erigeron Canadensis has strong similarities to Goldenrod; however, the differences are easy to spot when Erigeron Canadensis produces flowers and seeds out. Horseweed has white flowers.

The flowers have very yellow centers with forty to 50 white petals on each flower. Even at their full size, these flowers are only one-eighth of an inch across, so they are not easy to spot from afar.

The leaves are oval-shaped, narrow, and covered in tiny, white, stiff hairs.

The leaves are about a half-inch wide and four inches long at the plant’s largest size at full maturity.

Where Horseweed Grows

Erigeron Canadensis prefers full sun, loamy soil, and dry heat.

Horseweed can tolerate gravel and clay soil, though it is not favored.

Horseweed also prefers fertile soil; the more nutrients the earth has, the taller and more comprehensive it will grow.

It can tolerate droughts quite well, though it may drop some lower leaves in the process.

Erigeron Canadensis is native to Central and South America; however, it is considered invasive in Europe, Asia, and Australia. In the United States, it grows in every state, Hawaii and Alaska included.

Horseweed is a prolific producer that produces by seeds alone.

It creates approximately 700,000 seeds per pound, and the seeds are pretty hardy, clinging to animals and clothing for long distances before falling off and germinating.

Usually, the plant can be found in vacant lots, gravel parking lots, ditches, canals, roadsides, along railroad tracks, in meadows, agricultural crop fields, orchards, vineyards, and other unmanaged places.

Erigeron Canadensis Attracts Pollinators and Other Insects

The flowerheads attract a vast array of insects, including:

• Wasps
• Flies
• Honeybees
• Halictid bees
• Flower beetles

Horseweed is full of resin and poisonous, so most mammals leave it alone. Occasionally, deer and rabbits will selectively forage on young and immature Horseweed.

The flowers bloom from June through September, when you will commonly see these insects near them.