Common ragweed is a summer annual with origins in southwestern United States and northwestern Mexico and is common in the northeastern United States and southeastern Canada. This invasive weed highly pollenated flowers known to cause allergic reactions in humans, however, it is also notorious for causing crop loss in agriculture as well as growing in waste areas, roadsides, and gardens. The plant is highly resistant to drought and can grow in a wide variety of soil types with a preference to sterile soil. Common ragweed has ecological benefits to birds and insects within its habitat, attracting honeybees and birds to its oil-rich seeds and are especially valuable to birds during winter months as the spikes of seeds can remain above snow cover.
The plant can be identified by its fern-like leaves, cylindrical flower spikes that are made up of tiny green flowers, hairy stems, and a shallow fibrous root system. In its early stages of development, the seeds produce cotyledons that are dark green and thick. Early leaves will be hairy underneath and less hairy in full maturity. At full maturity, common ragweed can grow up to six feet tall, remaining upright and bushy. The seeds are usually dormant during winter months and will germinate in early summer months.
As one of the first weeds to develop herbicide resistance, successful common ragweed management requires before and after planting applications. Applying preemergence herbicides may reduce competition with crops and applying post emergence before the plant reaches over 4 inches may provide the best success for weed control.