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Statewide IPM Program, University of California

Hairy fleabane  (Conyza bonariensis)

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Life stages of Hairy fleabane mature plant flower head young plant seedling seeds

Hairy fleabane, a common summer annual or biennial broadleaf of disturbed, unmanaged areas and cultivated fields, may be confused with horseweed, Conyza canadensis. Hairy fleabane is found in the Central Valley, central-western region, and southwestern region, to about 3300 feet (1000 m). It inhabits agricultural lands and other disturbed areas competing strongly for water and growing rapidly.


Roadsides, agronomic croplands, landscaped areas, container nurseries, orchards, vineyards, ditch and canal banks, and urban sites, and disturbed, unmanaged areas.


The cotyledons (seed leaves) are gray green and about twice as long as wide, hairless or nearly so, with short stalks. Leaves are alternate to one another along the stem. The first leaf is oval to narrowly football shaped and sparsely or densely covered with hairs. Seedlings of hairy fleabane and horseweed are similar and difficult to distinguish. One feature to separate the two is that the leaves of hairy fleabane are gray green, narrower, and more crinkled than those of horseweed.

Mature plant

The mature plant can reach almost 4 feet (1.2 m) tall. It is well branched. Leaves are gray green and are covered with both short, stiff and long, soft hairs. Leaves are alternate to one another along the stem. Leaf edges range from smooth to weakly toothed or lobed. Upper leaves are linear to lance shaped. Lower leaves are generally egg shaped and taper to a short stalk. Although similar to horseweed, hairy fleabane branches more, has more basal leaves, and its stems usually branch near the base. Horseweed stems usually branch only in the upper half of the plant. Horseweed leaves only have short, stiff hairs, not a combination of short, stiff and long, soft hairs found in hairy fleabane. Fleabane typically is never over 4 feet (1.2 m) tall, but horseweed can reach over 9 feet (2.7 m) tall.


Flowers bloom from June through September. Upper branches contain many flowering stalks and there is one flower head per stalk. The flower head has a green, cup-shaped base formed by green leaflike structures (bracts) that overlap. The base tapers toward the top and encloses tiny, yellow flowers (disk flowers) that are surrounded by small, cream-colored bristles. As the fruit develop the head opens up and the bristles loosen.


The fruiting head looks somewhat like the “puffball” of a dandelion fruiting head but much smaller. It consists of bristle bearing seeds radiating outward, forming a fuzzy, spherical, cream-colored "head". 


Seeds are tiny, narrow, football shaped, or oblong, and approximately 1/17 of an inch (1.5 mm) long. Attached to the seed are brownish-white bristles that often redden with age. Horseweed bristles are mostly dirty white.


Reproduces by seed.

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