Redroot pigweed is an annual weed commonly found in waste areas and disturbed soils. It can attain a 2-4 foot height. The lower stems are reddish in color. Flowers are small and green, in bristly terminal and axillary clusters. A prolific seed producer, pigweed will produce up to 100,000 seeds per plant.
Seedlings are easily pulled or hoed from the garden. Older plants are more difficult to pull out and may scatter seeds in the process. Mulch will prevent seeds already in the soil from germinating.
When found in the lawn, pigweed can be spot-treated with herbicides containing MCPP, MCPA, and dicamba. In gardens, glyphosate (Round-up, Kleen-up) can be used, taking care not to get any of the chemical on desired plants. Pre-emergents containing oryzalin, pendimethalin, or trifluralin can be effective. When using a herbicide, be sure to read the label carefully and follow directions closely.
Photo: Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010