A meadow with thousands of plants of Helianthella quinquenervis (aspen sunflower, Asteraceae) at peak bloom. This species is a common long-lived perennial plant in meadows near the Rocky Mountain Biological Laboratory. This photo was taken during a year without frost damage. Compare the presence and density of sunflowers with the photograph of the same meadow in a year when frost damage killed...
Photo of a meadow with thousands of Helianthella quinquenervis (aspen sunflower, Asteraceae) plants. In the year that this photo was taken, a springtime frost killed all but a few flower buds. Compare with the photo of the same meadow in a year without frost. The lack of flowers in years having springtime frost has ecological consequences. There is no pollen or nectar for pollinators (bees and...
Results of a demographic study of Helianthella quinquenervis (aspen sunflower, Asteraceae) within plots at 2,900m at the Rocky Mountain Biological Laboratory. Note that seedlings are not common in most years, and the overall population seems to be declining. The lack of seedlings in most years is a consequence of frost damage to flower buds the previous year (so no seeds were produced). The...
Excavated plants of Helianthella quinquenervis (aspen sunflower, Asteraceae). H. quinquenervis is a long-lived perennial (some individuals can live 50-75 years). Note that each plant has multiple ramets from a single root.
Photo of an early-stage inflorescence of tall larkspur (Delphinium barbeyi) after a mid-June snowstorm at the Rocky Mountain Biological Laboratory. The buds were killed by the cold temperature. Like Helianthella quinquenervis, D. barbeyi is a frost-sensitive species.
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