Common Ragweed
Broadleaf weed
Common ragweed (Ambrosia artemisiifolia) is a fast-growing summer annual found across most of the United States. Gardeners and growers notice it because it is a heavy pollen producer and a persistent competitor in fields, gardens, and disturbed ground.
How to identify it
Look for finely divided, fern-like leaves that are deeply lobed and often hairy, usually green on both sides. Young plants form a low rosette, then send up branching, upright stems that can reach 1 to 4 feet or taller. Flowers are small and greenish, with the male flower spikes held in slender upright clusters at the stem tips. It grows from a shallow taproot with a fibrous, branching root system.
Where it grows
Common ragweed thrives in disturbed soil such as garden beds, crop fields, roadsides, fence lines, pastures, and neglected lots. It germinates in spring, grows through summer, and flowers from late summer into fall before frost kills it. It is an annual that spreads only by seed, and a single plant can produce thousands of seeds that stay viable in the soil for many years.
Why it is a problem
Ragweed competes with crops, vegetables, and turf for water, light, and nutrients, which can reduce yields and crowd out desirable plants. Its wind-borne pollen is a leading cause of late-summer and fall hay fever, triggering allergy and asthma symptoms in many people. Its large, long-lived seed bank makes an infestation hard to clear once it is established.
How to manage it
Because ragweed is an annual that reproduces only by seed, the goal is to stop plants from setting seed. Hand pull or hoe young plants while the soil is moist and the taproot is small, and remove them before flowering to keep new seed out of the soil. A layer of organic mulch in beds, close mowing on rough ground, and a dense, healthy stand of turf or cover crop all shade the soil and limit germination. Stay consistent over several seasons and avoid moving contaminated soil, since drawing down the seed bank takes time.
Commonly confused with
It is often confused with giant ragweed, which is much taller with large three-lobed leaves, and with mugwort or young marsh elder, whose leaves can look similar at a glance.
General guidance for US lawns and gardens, focused on prevention and non-chemical control. For a confirmed identification and options specific to your area, contact your local Cooperative Extension office. Page updated Aug 4, 2026.