IPMP3.0, Oregon State University, Copyright 2000

Biology and Management of Kochia


Registered Herbicides

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General Description:

Kochia (Mexican fireweed) is a summer annual that reproduces by seed. Plants are erect, 1 to 6 feet in height with multiple branches. Stems are smooth, green, much branched, from a few inches to over 6 feet high, growing from a taproot. Slender, alternate leaves are smooth on top and hairy below, 1 to 2 inches long, pointed, without petioles. Flowers are small, greenish, without petals, produced in axils of upper leaves and in terminal panicles. Seeds are about 1/16 inch long, oval, flattened with groove on each side, finely granular, surface dull, brown with yellow markings. Fragile star-shaped hull may enclose seed.

Individual plants may reach several feet in diameter, and up to 6 feet high. In fall, mature plants brak off at the base and tumble across fields scattering large amounts of seed.

Impact on Yield:

Kochia hinders harvesting operations and competes with mint for light, nutrients, and water. In one experiment in native spearmint, 2.3 kochia plants per square foot reduced the oil yield by 22 lbs per acre (Ian Heap).

Herbicide Control Notes:

  • Tough is very effective but has no residual Kochia control. Control is better when Tough is tank-mixed with Sinbar or used in repeated applications. Kochia often emerges too late for effective control with Gramoxone.