horseweed
Family
AsteraceaeScientific Name
Erigeron canadensisOther Common Names:
marestail
Synonyms (former Scientific Names):
Conyza canadensis var. canadensis
Erigeron canadensis
Leptilon canadense
Habit
Seedlings bear 2 to 3.5 mm long by 1-2 mm wide ovate hairless cotyledons. The spatula shaped first leaves are hairy on the upper side and at the leaf margin. Canada Fleabane reaches heights from 7.5 to 180 cm this highly branched plant is covered with short bristly hairs. The crushed plant is said to have a carrot-like scent. Canada fleabane has a fibrous root system.
Leaves
The alternate oblong or lance-shaped leaves are 2-10 cm long. The leaves are frequently bristly haired especially near the base and are short stalked. The leaves are smaller in size toward the top of the plant. These smaller leaves can be as large as 8 cm long and 1 cm wide they are stalkless with smooth margins.
Identifying Characteristics
Flowers white to yellow 3-5 mm across, Stems with numerous branches, carrot odor to crushed leaves and stem. Leaves contain herpene an irritant to the nostrils of horses. May cause skin irritations in some people. This plant is also an alternate host to several plant pathogens i.e. aster yellows, tobacco mosaic virus, and tobacco ring spot virus.
Flower Seed Head
White ray and yellow disk florets compose the numerous flower heads measuring 3-5 mm across. The ray florets are usually hidden by the floral bracts. The numerous flower heads are crowded in to terminal clusters.
Seed Fruit
The fruit an achene bears an oblong, yellowish-brown, and flattened seed that is usually less than 2 mm long. The pappus is white to tan in color. Plants are capable of producing 10,000 seeds
Where Found
Throughout Canada and the United States in cultivated crops, pastures, and meadows.
Growth Habit
upright and nonwoody
Thorns or Spines
not present
Approximate Flower Diameter
Varies:
pencil,
dime
Dominant Flower Color
Varies:
white,
yellow,
pink
Flower Symmetry
radial symmetery
Leaf Hairs
has hairs
Leaf Arrangement
alternate
Leaf Margin
serrated
Leaf Structure
simple
Leaf Stalk
none
Stem Hairs
has hairs
Stem Cross Section
round or oval
Milky Sap
not present
Root Structure
Varies:
fibrous,
taproot
Life Cycle
biennial
Ochrea
not present
Plant Type
Herb