Aquatic and Wetland Vascular Plants of the Northern Great Plains
49. Asteraceae, the Aster Family
12. Helianthus L. -- Sunflower2. Helianthus nuttallii T. & G. -- Nuttall's sunflower
Similar to the preceding and grading into it in the e part of our region, differing mainly as follows: Smaller in stature, 0.4-2 m tall; stem glabrous or sometimes hispid in the middle and lower portions, strigose in the inflorescence. Leaf blades narrowly lanceolate to lanceolate or ovate-lanceolate to elliptic, 4-15(20) cm long, 0.8-4.5 cm wide, entire to shallowly toothed, cuneate to rounded at the base; petioles 0.5-2(4) cm long. Jul--Sep. Wet meadows, marshes, shores, stream banks, ditches and other wet places; nw, c and e ND, across SD and e WY and s to c NE; (MN to Sask. and se B.C., s to NE, NM, AZ and CA). H. rydbergii Britt.
Two phases of H. nuttallii are encountered in our region. H. nuttallii subsp. rydbergii (Britt.) Long is most common, with mostly opposite, ovate-lanceolate to lanceolate or elliptic leaves, acute to obtuse at the tip. The other phase is subsp. nuttallii, with mostly alternate, linear-lanceolate to narrowly lanceolate leaves, acute to acuminate at the tip.
In the e part of our region where H. nuttallii and H. grosseserratus overlap in range, intermediate populations are found which cannot be assigned to either species with confidence.
Previous Section -- Helianthus grosseserratus Martens -- Sawtooth sunflower
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