Common Sunflower (Wild Sunflower)

What is common sunflower?

Common sunflower identification is rarely difficult: tall, sandpapery stems, broad toothed leaves with three main veins, and yellow flower heads with dark centers. Common sunflower (wild sunflower) identification gets trickier only when you need to separate it from its perennial cousins, which spread by underground stems or tubers. This native annual is the same species as the cultivated sunflower; its cultivated, wild and weedy forms interbreed freely.

It earns weed status in crop fields, gardens, pastures and along roads. A single uncrowded plant can set thousands of seeds, it emerges early and grows fast, and its deep taproot competes hard for water. On the plus side, quail, other birds and small mammals relish the large, oily seeds, so in a meadow, wildlife area or native planting you may decide to keep some.

Common Sunflower identification: what to look for

Feel a leaf and a stem first; few weeds are as rough as common sunflower. Then check whether each plant stands alone on a taproot or is part of a patch connected by underground runners, which would point to a perennial relative.

• Seedlings: Smooth, oblong seed leaves about 1/2 to 1 1/2 inches long, joined at the base, often above a purplish stem. The first one to three pairs of true leaves are opposite, toothed and stiff-haired.
• Leaves: Egg- to heart-shaped, 4 to 12 inches long, toothed and clearly three-veined, with stiff white hairs on both sides. Upper leaves are smaller, shorter-stalked and sometimes lance-shaped.
• Stems: Erect and thick, densely covered with coarse, spreading white hairs, often branching toward the top.
• Flower heads: 3 to 15 inches across, with 20 to 40 yellow ray petals around a red-brown to purple center, backed by two or three rows of overlapping, hairy green bracts. Only the central disk flowers set seed.
• Seeds: Flattened oval seeds roughly 1/8 to 1 inch long, white, gray, brown or black, often mottled or streaked.
• Roots: A single taproot with branching fibrous roots; no rhizomes or tubers.

Where it grows in the United States

Common sunflower is native to western North America and now grows in every part of the U.S., including Alaska and Hawaii, as well as much of Canada and Mexico. Oklahoma State notes it occurs throughout the country but is most common in the Midwest, and in the Great Plains it is both a familiar roadside wildflower and a serious weed in no-till corn, soybean and grain sorghum fields.

It handles poor, shallow or sandy soil, moderate drought, some salinity and brief waterlogging, but it will not tolerate shade. Expect it on disturbed, sunny ground: road shoulders, ditches, rights-of-way, field margins, waste areas, pastures, prairies and the edges of plowed fields.

Common Sunflower look-alikes

A few plants get mixed up with it:

• Prairie sunflower (Helianthus petiolaris): Another annual, but with much smaller heads (about 1 to 2 inches across) and narrower, triangular to lance-shaped leaves.
• Jerusalem artichoke (Helianthus tuberosus): A perennial that spreads by rhizomes ending in knobby, irregular tubers. Its leaves are narrower and its heads smaller (roughly 2 1/2 to 3 1/2 inches), and it comes back from the same patch every year.
• Texas blueweed (Helianthus ciliaris): A creeping perennial with rhizomes, only about 2 1/2 feet tall, with lance-shaped, blue-green leaves instead of broad, rough, heart-shaped ones.

How to get rid of common sunflower

Pulling, digging and mowing: Pull seedlings and young plants by hand while the soil is moist; the taproot comes out cleanly when plants are small. For larger plants, cut the stem below the crown with a sharp hoe or spade; a shoot severed from its root cannot regrow from the root alone. In fields and pastures, cut or mow before heads mature. Because most seed left on the surface dies within a winter or two, one season of stopping seed can turn a heavy infestation into a manageable one. In mulched beds, don't count on mulch alone: the large, food-packed seeds let seedlings push up through even a thick layer, so walk your beds and pull volunteers while they are small.

Cultural control matters most, because the right conditions keep it from coming back.

• Keep soil covered: winter grains and other dense canopies suppress emergence.
• Skip fall tillage, which buries seed where birds and mice cannot eat it; seed left on the surface is eaten or dies over winter.
• Graze or mow infested stubble to cut seed production.
• Clean soil off tires, mowers and equipment that have worked infested roadsides or fields.

Herbicides: For a handful of plants, pulling or cutting beats any herbicide. For larger patches in pastures, Texas A&M AgriLife lists glyphosate applied with a wick or wiper applicator during active growth; livestock must be kept off for the waiting period stated on the label. Any product you use must be labeled for your site (pasture, crop, roadside, lawn or bed), and you must follow the label exactly, because the label is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Common sunflower spreads only by seed. Most seed on the soil surface does not survive past its first winter or two, but seed buried about 8 inches deep has lasted at least 17 years. So the best prevention is simple: do not let plants drop seed, and do not till fresh seed under. Pull volunteers in spring when they are easy to spot.

Watch for seed brought in on equipment or in road-ditch soil used as fill. If you want sunflowers for wildlife or looks, plant them where volunteers will not matter and cut heads before seed falls near gardens or crop ground.

Questions we get about common sunflower

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