Hairy Fleabane-Sunflower Family

Flaxleaved fleabane

Conyza bonariensis

Characteristics. This native of the American tropics is an annual that normally emerges in February, but can emerge in December if winter temperatures are warmer than average. It is commonly found in lawns, cultivate fields, meadows and waste areas. This plant can withstand several mowings and still produce seed. It is extremely competitive for water and grows rapidly. With a deep taproot it can survive in dry conditions once established.

Identifying Characteristics. Hairy fleabane seedlings are covered with short, soft hairs and exhibit narrow leaves which are often wrinkled or appear slightly distorted. Gray-green seed leaves are about twice as long as they are wide. Mature plants are 1/2 to 3 feet tall and well branched. 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. 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.

Hairy fleabane may be confused with horseweed. Both plants grow in the same areas, but hairy fleabane has a more branching growth habit with more abundant basal foliage.

Flowers are small (1/2 inch in diameter), dull white, and found on the upper parts of the branches.

Characteristics Important to Control. Paraquat and glyphosate will control this species when it is small, but once plants bolt (sending up flowering stalks), they will not control it. Glyphosate at 1 lb a.i./acre will control plants up to 13 leaves; for plants with 14 to 19 leaves 2 lb a.i./acre is required. Plants larger than 19 leaves are not adequately controlled. Plants of a close relative, horseweed, have developed resistance to glyphosate in many parts of the Unites States. Thus, it is critical to monitor control efforts and follow up with hand weeding to prevent escape of any plants that might be resistant.