Wildflowers have a fear of trees! A new project begins.

by Richard B. Primack

“Don't be afraid that your life will end, be afraid that it will never begin!”

-Henry David Thoreau

We have received a new NSF-funded project to determine if trees in the eastern United States, like oaks and maples, respond more rapidly to a warming climate than spring woodland wildflowers, like trout lilies and anemones. If so, the wildflowers might be getting shaded out in spring, reducing their ability to mature their fruits in summer and to grow and flower in later years. This is an example of an ecological mismatch between different species, in this case trees and wildflowers, and could lead to the decline of woodland wildflowers.

Trees such as this big-toothed aspen are leafing out earlier in the spring.

This work builds on the observations of famous environmental philosopher Henry David Thoreau from the 1850s in Concord, MA, combined with our own observations from 2004 to the present, which show that trees leaf out earlier now than in the past and wildflowers are flowering earlier.

Wildflowers, such as this pink lady’s slipper orchid, might be shaded out by trees in coming years.

We are using herbarium specimens, which are plant museum specimens, to extend our study across the entire eastern United States. Much of this work is being carried out by BU grad student Tara Miller with help from others.

Colleagues in China and Germany will carry out comparable studies, allowing us to determine if this mismatch between trees and wildflowers is really a global phenomenon. 

Mason Heberling at one of the Pittsburgh field sites.

Our co-PIs on this grant, Mason Heberling at the Carnegie Museum and Sara Kuebbing at the University of Pittsburgh, will carry out complementary experiments to determine the combinations of temperature and photoperiod that trees and wildflowers use to start their spring activity.  They will also measure photosynthetic rates of wildflowers to determine how they respond to reduced light levels.

This work was recently covered by the Daily Free Press.