When Spring Comes Early: Shifting Bloom Times of Piedmont Ephemerals

Spring ephemerals are woodland plants that bloom early in Spring, capturing sunlight that hits the forest floor before the trees leaf out. Some of these ephemerals, like Trout Lilies (Erythronium sp.) have colonies that are over 100 years old!

We see spring ephemerals, their delicate leaves and incandescent flowers, during their epigeous or above ground phase, but these season-adapted plants spend most of their life in a hypogeous or below ground phase, reliant on extensive mycorrhizal associations to get water.

During the spring, when temperatures fluctuate wildly, many spring ephemerals close up in the cold. This opening and closing of blooms, and sometimes leaves, is called nastic movement. Some flowers exhibit nastic movement in response to day-length (i.e., photonasty where increases in light trigger the production of the hormone auxin, which causes cells to grow) or temperature (i.e., thermonasty where liquid warms in the cells at the base of flowers, causing the cells to expand the the flowers to open). Photonastic and thermonastic movement can help protect pollen when the weather is bad.

In the Piedmont of North Carolina, researchers in the Duke Forest (e.g., Alex Motten) in the 1970s and 1980s spent a lot of time looking at phenology, or the timing of cycling natural phenomena such as blooming or leaf burst.

Figure 1. Bloom times for Spring flowers in the Duke Forest in 1979 from Alexander F. Motten, “Pollination Ecology of the Spring Wildflower Community of a Temperate Deciduous Forest,” Ecological Monographs 56, no. 1 (February 1986): 21–42, https://doi.org/10.2307/2937269.

Key to numbers: 1. Hepatica americana (DC.) Ker; 2. Erythronium umbilicatum subsp. umbilicatum Parks; 3. Sanguinaria canadensis L.; 4. Claytonia virginica; 5. Thalictrum thalictroides (L.) Boivin; 6. Cardamine(Dentaria) angustata 0. E. Schulz; 7. Stellaria pubera Michaux; 8. Viola papilionacea Pursh; 9. Uvularia sessilifolia L.; startfl; 1O.Tiarella cordifolia var. col/ina Wherry; 11. Uvularia perfoliata; 12. Chrysogonum virginianum L.; 13. Podophyllum peltatum L.; 14. Trillium catesbaei Elliot; 15. Amsonia tabernaemontana; 16. Iris cristata; 17. Cercis canadensis L.; 18. Aesculus sylvatica Bartram; 19. Cornus florida

Since these earlier studies were published, researchers have found phenological changes across taxa associated with various metrics of climate change, especially the timing of snow melt and average spring temperatures. For example, Rebecca M. Prather and colleagues (2023) found that for plants in temperate areas, increasing average spring temperatures correspond with earlier phenological activity. Some changes in phenological activity responded to lags up to two growing seasons prior. For example, hotter summers one and two years prior result in earlier phenological activity for both plants and amphibians!

Here in the Piedmont of North Carolina, I’ve been taking notes, photographing spring ephemerals, and recording bloom dates in Durham, Orange, and Wake Counties for 20 years, since 2005. Below you can see a chart of my own records of bloom dates (written as day of the year, e.g., Day 32 = Feb 1) by year. The overall trend supports the work of other researchers suggesting earlier bloom times for spring ephemerals as the climate warms and spring temperatures increase sooner.

Figure 2. Bloom first bloom dates of spring ephemerals [Bloodroot (Sanguinaria canadensis), Dutchman’s Britches (Dicentra cucullaria), Hepatica (Hepatica sp.), Rue Anemone (AKA Windflower, Thalictrum thalictroides, Anemonella thalictroides), Spring Beauty (Claytonia virginica), and Trout Lily (Erythronium americanum and Erythronium umbillicatum)] in the Piedmont of NC (2005-2025), collected by Nicolette L. Cagle. Includes a trend line for Spring Beauty’s (Claytonia virginica) earliest noted bloom time.

Photos of Spring Ephemerals in the North Carolina Piedmont (primarily Durham County, also Orange and Wake Counties) between 2005 and the present.

Jump to Bloodroot (Sanguinaria canadensis), Dutchman’s Britches (Dicentra cucullaria), Hepatica (Hepatica sp.), Rue Anemone (AKA Windflower, Thalictrum thalictroides, Anemonella thalictroides), Spring Beauty (Claytonia virginica), and Trout Lily (Erythronium americanum and Erythronium umbillicatum).

Bloodroot (Sanguinaria canadensis)

Dutchman’s Britches (Dicentra cucullaria)

Hepatica (Hepatica sp.)

Rue Anemone (AKA Windflower, Thalictrum thalictroides, Anemonella thalictroides)

Spring Beauty (Claytonia virginica)

Trout Lily (Erythronium americanum and Erythronium umbillicatum)

References

• Alexander F. Motten, “Pollination Ecology of the Spring Wildflower Community of a Temperate Deciduous Forest,” Ecological Monographs 56, no. 1 (February 1986): 21–42, https://doi.org/10.2307/2937269.
• Rebecca M. Prather, Rebecca M. Dalton, billy barr, Daniel T. Blumstein, Carol L. Boggs, Alison K. Brody, David W. Inouye, Rebecca E. Irwin, Julien G. A. Martin, Rosemary J. Smith, Dirk H. Van Vuren, Caitlin P. Wells, Howard H. Whiteman, Brian D. Inouye, Nora Underwood; Current and lagged climate affects phenology across diverse taxonomic groups. Proc Biol Sci 1 January 2023; 290 (1990): 20222181. https://doi.org/10.1098/rspb.2022.2181