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Pest Information



  • Latin Name: Conyza Canadensis
  • Common Name: Horseweed
  • Other Names: Mare’s tail, colt’s tail, cow’s tail, butter-weed, pride-weed, Canada fleabane, fleabane

Pest Details



Native to North America and widely distributed throughout the continent.


A winter or summer annual with seeds geminating in the summer or fall to form a basal rosette of leaves. As the stem elongates these basal leaves tend to deteriorate. The central stalk of the plant can grow over 6 feet tall as a thick, strong stem that persists well into the winter. Reproduction is only from seeds, and plants grow easily in almost any soil condition, including cultivated crops. It is a common and conspicuous roadside weed that forms dense forests of the tall plants.


Mature plants have a tall central stem that is very hairy and has a bristly feel to it, with extensive short branches along the upper half. Leaves are alternate along the stem and are long and thin. The stem is crowded with these leaves that grow on stalks that taper into the leaf itself. The leaves also are hairy. Flower heads are extremely numerous and occur at the ends of the many branches off of the upper stem, but each flower head is inconspicuous as it remains mostly closed and wrapped by the bracts. The petals within this consist of white ray flowers and yellow disc flowers. The mature seeds have a pappus of long bristles that enable the wind to carry them long distances.

Characteristicts Important to Control:

An annual weed easily removed by hand, but there can be a heavy growth of seedlings around the parent plant, causing thick growth of the plants.

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