Biology and Management of Kochia
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: