A look at phenology, the study of how plant and animal cycles are influenced by temperature, rainfall and day length.

Citizen scientists are helping build a map that shows where the common lilac is leafing out.

Phrenology was a 19th century theory that personality tendencies could be inferred by the bumps and depressions on a person’s skull. The word phenology sounds similar but is a very different and much more reliable science with great value for gardeners.

Phenology is the study of how plant and animal cycles are influenced by changes in seasonal and climactic factors such as temperature, rainfall and day length. A phenologist tracks events like the first appearance of robins in spring, when apple trees or lilacs flower, when geese begin migrating south or when trees start to change color in the fall.

Leonard Perry, Extension Professor of Horticulture at the University of Vermont writes:

Tracking the dates of biological events began in 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 1,200 years. This type of information is often handed down as folklore, such as the saying about spring bud break and rainfall: “If oak’s before ash, you’re in for a splash. If ash before oak, you’re in for a soak.”

When Dr. Perry first arrived at the University of Vermont in the 1980s, he took over some phenology work begun in 1965 by a Professor Hopp, who tracked bud and bloom times for certain selections of lilac and honeysuckle. Since then, the original work has been greatly expanded by other curious minds, such as geography professor Mark Schwartz at the University of Wisconsin–Milwaukee, who is currently chairman of the National Phenology Network.

Farmers and gardeners have always found phenology information valuable for predicting events such as first frosts, the arrival of certain pests and expected harvest times for crops. Scientists attempting to understand and quantify climate change, are finding these phenology records incredibly valuable.

To get a sense of just how interesting and useful phenology information can be, check out the “citizen scientist” phenology network called Project BudBurst. Right now, you can see live maps that indicate where 75 native species of trees, shrubs, grasses and wildflowers are leafing out or coming into bloom. It’s easy to contribute data about what’s happening where you live. Check out this live map that shows where the common dandelion is blooming. Or this one, which shows where the common lilac is leafing out. Click on the markers to see details.

Happy spring!

Kathy LaLiberte, Director of Gardening, Gardener’s Supply