Pat Pearson and Eddy Anderson, Arizona Master Naturalists, and observing lilacs south of Tucson, on the Santa Rita Experimental Range. (Photo courtesy USA NPN)

Each growing season, gardeners yearn to learn the crucial dates indicating spring planting and first frost in fall.
Seeking reliable guidelines, growers have regularly referred to the color-coded zone maps printed on the backs of seed packets, or their state Extension service.
But lately, apparent changes in Mother Nature’s timelime, affected by warming worldwide temperatures, seem to be meddling with those once certain standbys.
Plants bud and bloom earlier than traditionally expected, and birds normally associated with southern skies are spotted farther north with more regularity.
Enter the old folk science of tracking visual signs, phenology, which in recent years has reemerged as a vital tool in coping with ever more noticable climate related changes.
Adages advising the planting of peas when forsythia blooms and tomatoes when dogwood flowers peak, once regarded as “old wives tales” or “old farmers lore,” are now gaining renewed credence, as changes in the natural rhythms of ecosystems become inescapably noticable in one’s own backyard, impacting the once predictable growing cycles.
According to, a Chicago Botanical Garden project, Phenology is “literally the ‘science of appearance” — the word itself stemming from the Greek phainos (“to show or appear”) and logos (“to study”).
Dedicated gardeners have often kept journals to refer back to from year to year.
Such valuable records have also been maintained by naturalists, notably Henry David Thoreau, author of the 19th century classic Walden, and Aldo Leopold, whose conservationist essays describing his family’s remote farm life landscape in the 1930s and ’40s were compiled as “A Sand County Almanac.”
Programs such as Budburst, and especially the USA National Phenology Network are at the forefront of coordinating organized outreach to facilitate wider observation and recording efforts.
USA NPN defines phenology as “nature’s calendar—when cherry trees bloom, when a robin builds its nest and when leaves turn color in the fall.”
Changes in such vital phenophases are among the most sensitive biological responses to climate change, the organization’s website explains, adding:
“Across the world, many spring events are occurring earlier—and fall events are happening later—than they did in the past. However, not all species are changing at the same rate or direction, leading to mismatches.
How plants and animals respond can help us predict whether their populations will grow or shrink – making phenology a “leading indicator” of climate change impacts.”
Locally, Salisbury University is among USA NPN’s many wide-ranging partners including academics, research scientists, policy makers, educators, resource managers, and citizen scientists.
In 2021, SU Biology Department Professor Kim Quillin initiated SUPP, the Salisbury University Phenology Program.
“My role in the SUPP program was to create it as a Course-Based Undergraduate Experience for our new Introductory Biology sequence. I conceived of the project, selected the trees, wrote the curriculum, and continue to oversee it as a partner with the National Phenology Network,” Quillin noted.
Two additional faculty members teaching Biol 202 (Introduction to Evolution and Ecology) along with Quillin, Dr. Chelsea Berns and Dr. Richard Wilkins, are also involved with guiding students through the protocols of observing and recording relevant data from 120 tree specimens of nine native species (40 of each at three sites throughout the campus).
Students record observations into NPN’s publicly accessible “Nature’s Notebook” app, during the fall and spring semesters.
“We are in the process of extending the SUPP research project to include Biol 201 (Introduction to Molecular and Cellular Biology),” Quillin added.
The trees being studied include Red, Silver, and Sugar Maples, Canadian serviceberry, Eastern redbud, Sassafras, Willow and Pin oaks, and Flowering dogwood.
One of this spring’s student teams compared the timing of flowering in Flowering dogwoods (Cornus florida) compared to last spring on SU’s campus.
The graphed results show that flowering occurred much earlier this year due to the exceptionally warm spring, Quillin said.
Dogwoods and lilacs make up one of a number of USA NPN’s regional campaigns that observers can participate in. Others include Pest Patrol, Nector Connectors, the Green Wave (Spring leaf out and Fall color), Quercus Quest (Oaks), and Redbud Phenology Project.
Lilac observations, stemming from the 1950s, are known as the “lilac legacy project,” developed by University of Montana Professor Joe Caprio, according to Alyssa H. Rosemartin, currently the organization’s Partner and Application Specialist.
Back in 1956, Caprio, a newly hired assistant professor with a degree in Agricultural meteorology, decided to focus his research efforts on learning about the state’s plant climatology.
To that end, he set out to map the state’s growing temperatures by enlisting more than a hundred volunteers to observe and record three stages of development in the hardy common purple lilacs which seemed to grow everywhere.
The undertaking became the state’s first phenology survey.
Soon the program was expanded throughout 11 Western states, with 1,500 volunteers recording simple data on mail in cards.
Rosemartin recalled seeing Caprio’s original hand-drawn topography maps and long handwritten reports.
“A handful of original volunteers were still mailing in cards with paper data,” she said.
The program lagged for several years following Caprio’s early 1990’s retirement.
But his trailblazing efforts ultimately inspired the eventual creation of a comprehensive USA-NPN in 2007 by co-founders Dr. Mark Schwartz and Dr. Julio Betancourt.
Today, observers can choose to study natural or cloned lilacs (or dogwoods).
The cloned specimens allow those analyzing data to focus on purely environmental changes.
When asked about data indicating spring’s arrival in this region, Rosemartin quickly referenced the top ten earliest spring arrivals, from 1983 through 2023, indicated by NPN’s leaf index for Baltimore, Anne Arundel, Dorchester and Wicomico counties.
Sure enough, 2023 marked the earliest spring in Baltimore, and the second earliest in the other three, she noted. “But the spring of 2017 was also really dramatic, drawing a lot of media attention.”
For those interested in signing up to become a Citizen Scientist observer, Rosemartin recommends visiting
For more information on SUPP, contact Dr. Kim Quillin at