Flower:

One to 7 flowers at the top of the plant, most often 1 to 3. Individual flowers are 2 to 3 inches across with 8 to 15 ray flowers (petals) and 40+ yellow center disk flowers. Rays are sterile; the 5-lobed disk flowers have a 2-parted yellow style and a dark brown column of stamens that have a small yellowish to brown appendage at the tip.

Surrounding the base of the flower are 3 or 4 layers of lance-shaped, sharply pointed bracts (phyllaries), each phyllary usually irregularly fringed with short hairs around the edges, often stiff hairs on the surface, and the tip loose and ascending to spreading to curved. The set of phyllaries (involucre) is up to about ½ inch long (8 to 14 mm) and to 1 inch (10 to 25 mm) diameter.

Leaves and stem:

 Leaves are mostly opposite, 2½ to 7 inches (6.5 to 18 cm) long and up to 3+ inches (8 cm) wide, narrowly lance to egg-shaped, broadest at or near the base, toothless to irregularly toothed, tapering to a sharply pointed tip, wedge-shaped to rounded to straight across at the base, the blade with 3 main veins, the lateral veins joined just above the base of the blade. Both surfaces are at least sparsely covered with short stiff hairs, the lower surface also gland-dotted.

Leaf stalks are usually less than ¾ inch (4 to 20 mm) inch long, about ½ inch long mid-stem; uppermost leaves may be stalkless or nearly so. Stems are erect, unbranched, variably covered in stiff hairs, though the hairs can wear off leaving at least the lower stem smooth or with rough-textured stubble. Loose colonies may form from long rhizomes.

Fruit:

The center disk forms a head of dry, brown seed, each seed up to 4.5 mm (~¼ inch) long and lacking a tuft of hair, but with 2 bristle-tipped scales at the top.

Notes:

Hairy Sunflower reaches the northwest edge of its range in Minnesota, where it is found in a range of habitats including woodland edges, roadsides and open grassy areas. While references state it may grow as tall as 6 feet (2 meters), 3 to 4 is pretty common. It is most similar to the related Woodland Sunflower (Helianthus strumosus) and the two overlap in a number of traits, which can make it difficult to distinguish them.

Helianthus hirsutus typically has 1 to 3 flower heads per stem, occasionally has as many as 6 or 7; stems are at least sparsely covered in stiff hairs, though hairs can wear off with age; leaves are broadest at or near the base, stiff-hairy on both surfaces, gland-dotted on the underside, and have 3 major veins, the lateral veins joining the midvein just above the leaf base; leaf stalks on mid-stem are ~½ inch long. It is noted that the column of stamens on the disk flowers has an appendage at the tip that is commonly yellowish, less often brown.

By comparison, H. strumosus is likely to have at least 5 flowers and as many as 15, leaf surfaces may be hairless or have some matted hairs on the underside, leaf stalks may be an inch or more long, and the stamen column on disk flowers is said to have a dark brown appendage. I do question the color of the appendage being anything approaching diagnostic since yellow appears to be common on many sunflowers, and the hairiness of leaves seems to vary depending on the reference (e.g. Gleason & Cronquist vs. Flora of North America), so H. strumosus is worth revisiting in the coming season. Another woodland sunflower species, Helianthus divaricatus, not present in Minnesota but is in Wisconsin, is also very similar overall, has leaves that are all stalkless, and hairless stems.