University of Vermont Extension 
Department of Plant and Soil Science

Anytime News Article

Dr. Leonard Perry, Extension Professor
University of Vermont
Watching when buds and then flowers appear on specific plants from year to year now is being used to watch for changes in climate.  Knowing these dates also can be related to the appearance of certain pests and diseases, so can tell you the best times for control.  The study of such biological events is known as “phenology.”  It is easy, once you know a few tips, and now you can join a national network of gardeners and naturalists all sharing this interest.
The appearance of robins in spring, flowering of crabapples and lilacs, and the flowering of the cherry trees in Washington are all phenological events.  They respond to a combination of climate factors such as temperature, rainfall, and daylength.  Of course these can be measured separately, but what I find fascinating about watching plants is that they are programmed to combine all such factors to determine when certain events such as bud opening occur.
Watching dates of biological events each year is not new, dating back centuries to pre-agricultural times.  The earliest written records were by the Chinese in 974 B.C.  The Japanese have been monitoring peak cherry tree bloom for 1200 years.  The famous Swedish botanist of the 1700’s Linnaeus is considered a cofounder of the study of phenology.  The word actually comes from the Greek words for “study” of “appearances.”  Another cofounder of phenology was a British landowner, Robert Marsham, whose family kept detailed records for a couple hundred years.  Phenology has been handed down for years in folklore, such as the saying relating leaf appearance and rainfall. "If oak's before ash, you're in for a splash. If ash before oak, you're in for a soak."
Much of the current phenology efforts can be traced back in part right here to Vermont, to the research and network begun in 1965 by Professor Hopp in the Department of Plant and Soil Sciences.  I took over this network in the early 1980’s, at that time collecting bud and bloom data on certain selections of lilac and honeysuckle.  Since then, this network has been expanded under Dr. Mark Schwartz at the University of Madison Milwaukee.  The current result is the National Phenology Network where you can learn more about this science (  You can become involved with many across the country in their latest effort, Project Budburst (
The goal of Project Budburst is to gather phenology data on several dozen native tree, shrub, and flower species, over many years, and over all regions.  This data then can be used to track any changes in climate.  Even if you just monitor your own plants without sending this project the dates of certain events, you can get a feel over the years of whether the climate in your own area is changing. 
The website for Project Budburst has some very useful information for your monitoring, with descriptions of events such as first leaf, full leaf, first flower, full flower, and end of flower.  There is a map you can click your state for a list of possible native plants to watch for such events.  For instance, in Vermont there were about 30 possible plants listed.  Of these, some are more common such as American linden, aspen, black locust, box elder, chokecherry, dandelion (yes, you can even monitor weeds!), yarrow, white pine, large-flowered trillium, common lilac, paper birch, red maple, and red osier dogwood (the shrubby one with red stems). 
When you pick a plant or two to watch, make sure you chose a species and not a cultivar (cultivated variety).  With lilacs, for instance, depending on the cultivar, you might see first bloom from the second week of May to the second week of June. 
Many more details on phenology, climate change, details and photos of all the plants, and how to participate as a “citizen scientist” are on the Project Budburst website.  Through participation in this program which is easy, and doesn’t require much time (outside of what you probably already are doing in watching your plants in spring and summer), you will be learning more about your climate.  You’ll be helping scientists in their predictions, taking the “pulse of the planet.”  And you can begin to relate certain events, such flowers and pests.  More information on this is available in Integrated Pest Management checklists from the University of Massachusetts ( 

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