Flower:

One to 6 flowers at the top of the plant, often 2 or 3 clustered at the stem tip and sometimes 1 or 2 arising from the uppermost leaf axils. Individual flowers are 2 to 3 inches across with 10 to 21 ray flowers (petals) and yellow center disk flowers.

Surrounding the base of the flower are 2 to 3 layers of narrowly triangular, sharply pointed bracts (phyllaries), each phyllary usually with a fringe of short hairs around the edges especially near the base, and often stiff hairs on the surface. Phyllaries are loose and somewhat spreading.

Leaves and stems:

Leaves are 2 to 8 inches long and to 1½ inches wide, narrowly lance to egg-shaped, toothless to shallowly toothed, sharply pointed to blunt at the tip, wedge-shaped to somewhat rounded at the base, on a stalk up to ½ inch long. The upper surface is hairless or with a few short hairs, the lower surface rough from short, stiff hairs. Leaves are mostly opposite though may be alternate on the upper stem.

Stems are erect, hairless to sparsely short-hairy, green to yellowish or sometimes purplish, single or a few from the base, sometimes branched in the upper plant. Plants have short rhizomes and tuberous roots.

Fruit:

The center disk forms a head of dry seed each up to 5 mm (~¼ inch) long and without a tuft of hair, but with 2 bristle-tipped scales at the top.

Notes:

Nuttall's Sunflower is uncommon in Minnesota, where it reaches the eastern edge of its range in our western counties, though disjunct populations have been found in Canada as far east as Quebec. Habitats are primarily in open, moist to wet prairies and meadows. According to the DNR, there have only been about 15 documented locations, about half of which are over 50 years old that have not been relocated. They note one possible cause of its rarity is the perception that sunflowers are a difficult group to ID, so when encountered they have a tendency to be skipped over. I know that feeling pretty well. Due to its probable actual rarity in the state and lack of knowledge on its specific habitat requirements in Minnesota, it was listed as a Special Concern species in 1984.

Nuttall's Sunflower is recognized by leaves mostly opposite (opposite or alternate on the upper stem), toothless to shallowly toothed, on stalks up to ½ inch long; stems are hairless to sparsely hairy; just 1 to 6 flower heads at the top of the stem. While it's been documented as reaching 8+ feet tall, 5 feet is more common. It bears a resemblence to both Giant Sunflower (Helianthus giganteus) and Sawtooth Sunflower (Helianthus grosseserratus), both of which may have as many as 12 to 15 flower heads per stem. Giant Sunflower leaves are all or mostly alternate and coarsely toothed to nearly toothless, and stems are consistently hairy; Sawtooth Sunflower leaves are more consistently sharply toothed, leaf stalks are up to 1½ inches long, and stems are hairless and usually covered with a waxy bloom.

There are 3 subspecies of Helianthus nutallii: subsp. parishii, restricted to California (possibly extinct), has long hairs on leaves and phyllaries; subsp. nuttallii, found from South Dakota westward, has mostly alternate leaves with sharply pointed tips; subsp. rydbergii, found from Minnesota westward, has mostly opposite leaves with pointed to blunt tips.