Climate warming is causing Mundy wildflowers to flower earlier
Shown above: Hepatica (H. acutiloba) and bloodroot (Sanguineria canadensis) grow in the Mundy Wildflower Garden.
Three decades of research in the Mundy Wildflower Garden shows some spring plants blooming as much as two weeks earlier today, with serious implications for delicate ecosystems
David Weinstein, Senior Research Associate, Cornell Department of Natural Resources
Since 1985, a dedicated group of volunteers has been recording the date of first flowering for all 503 plant species found in the Mundy Wildflower Garden. These records detailed observations made each day of the growing season. This special collection of continuous observation has been rarely duplicated elsewhere. The data are now playing a major role in uncovering the effect climate change is already having on plants, and helping to unravel the mystery of why some plants are affected, while others are not.
David Weinstein, a researcher in the Department of Natural Resources at Cornell and a member of the Cornell Botanic Garden Advisory Council, has begun documenting how much warmer it is in the wildflower garden now, and identifying which plants are flowering much earlier than they had in previous years, because of the warming trend in climate.
Since 1970, the average annual temperature at the official Cornell University weather station, located close by the wildflower garden, has increased 1.8°F. The number of growing-degree days (days with an average daily temperature above 40 degrees F) accumulated (starting January 1 each year) triggers spring plants to begin flowering. In 2017, the number of growing degree days (GDD) on May 1 was nearly double what it had been historically by this date. We have begun making weather measurements directly in the wildflower garden with the installation of a weather station in 2016.
Because of these climate changes, some early spring ephemeral plants in the wildflower garden, such as skunk cabbage (Symplocarpus foetidus), hepatica (Hepatica acutiloba), and bloodroot (Sanguinaria canadensis), are flowering 10 days to 2 weeks earlier than they did 30 years ago. Twenty one percent of the plant species in the Mundy Wildflower Garden have had their day of first-flowering significantly changed over the last 15 years. On average, for every increase of 17 growing degree days, the flowering of each plant species has been advancing one day.
Unfortunately, one of the plants that has moved its date of first flowering earlier in the year most consistently over the past 30 years is the invasive garlic mustard. This means that garlic mustard is increasingly able to gather essential resources needed for growth earlier and earlier compared with other spring plants, making it ever more successful at invading those other plant’s territories.
The earlier flowering of some plants, such as common milkweed (Asclepias syriaca) and black-eyed susan (Rudbeckia hirta), could potentially help specialized insects that depend of these plants, but whose populations have been declining, such as monarch butterflies and bumblebees. Unfortunately, there is some evidence that periods of activities of these insects is becoming disconnected from the timing of when the plants are flowering, a trend that could spell disaster for the ecosystems built on the synchrony of plants, insects, birds, and other animals.
We would not have any way of knowing this without the long-term dedicated efforts of the volunteer observers, data collectors, database compilers, and organizers over the last 30 years. We especially thank Susanne Lorbeer (observer extraordinaire); Rosemarie Parker (magnificent database organizer); Donna Levy, who began this effort; Krissy Boys, through whose careful gardening these plants thrive; and Betsy Dain. These efforts demonstrate how citizen scientists, the professional gardening staff, and Cornell researchers can collaborate to use the Botanic Garden collections as a vital resource to help us understand what is happening to our world.
