Read Time: 3 min
By Mitchell Hennings, Land Steward for Wildlife & Habitat
You may have noticed on your outdoor walks and adventures that this year’s trees, shrubs, and flowers began to greet you much earlier in the season, blooming and filling in the gray and brown spaces of the woods with their intricate flowers and leafing patterns. If you noticed this, you might have also wondered why this occurs. Are the plants confused? Are their calendars mixed up? Or is something much larger at play that is influencing plant behavior across the country?
Plants can sense subtle changes within their environment, whether it be early rain or lack thereof, increased photoperiods (longer exposure to the sun), frequent disturbances, or intense weather events. These variables impact how plants progress through their stages of growth to sprouting leaves, fruiting, or developing flowers. Yet, if the timing involved in these processes is off by days or even weeks, like we are now experiencing, there can be untold impacts on the plants whose growth is regulated by it.
This year, plants began to leaf out and fill our forests and roadsides with green earlier than usual, but these growing plants are not naturally occurring in our environment. Plants like Honeysuckle, Bittersweet, Autumn Olive, Multi-Flora Rose, Barberry, and Norway Maple all leaf out much faster than our native plants. These invasive plants had either full leaves or were beginning to bloom before native plants and trees had even begun to produce leaves. The faster phenology of the invasive plants is a clear competitive advantage over the native plants, as they have longer flowering periods and a higher chance of attracting pollinators and going to seed sooner (Kherberger & Holzschuh 2019). This behavior puts increased pressure on native plants to adjust their flowering period earlier in the season, but this may prove to be even more of an issue. If these native plants adjust their flowering period, they could then be impacted by sub-optimal temperatures, low pollinator activity, and a higher chance of dying off (Kherberger & Holzschuh 2019).
Another well measured variable that has been found to contribute to the forward progression of early leaf onset is the decrease in precipitation events. An article published in the journal Nature details a study conducted to understand the impacts of precipitation on native and nonnative plants and how those complex interactions impact leaf onset date, which is when plants produce leaves (Wang et al. 2022). When there are decreased precipitation days, there are also decreased cloudy days to allow for radiation absorption by the plants, which is what signals plants to begin producing leaves (Wang et al. 2022). You don’t need to be a scientist to notice the decrease in rain over the years during the spring season. The adage “April showers bring May flowers” used to ring true ten or twenty years ago, but in today's climate, it looks like flowers bloom in early April, leaving May irrelevant.
Sources:
https://www.nature.com/articles/s41598-019-51916-0
https://www.sciencedaily.com/releases/2022/02/220217155232.htm
