Helianthus maximiliani Schrad.
This tall, vigorous plant provides sunny late-season color for the back of the border. Cultivars are available that bloom earlier for shorter-seasoned areas. Perennial sunflower prefers more water than many other Wyoming natives. Lack of sufficient supplemental water will produce significantly shorter plants with smaller blossoms. This perennial reseeds and can spread aggressively by rhizomes in some situations; however, limiting supplemental irrigation can help keep it under control.
Water needs: moderate
Exposure: full sun
Availability in nurseries: common
Native range: native to most of the U.S. (WY native)
Plant family: Asteraceae
Photo by Jennifer Thompson