Regional Gardening Reports :: National Gardening Association

In the Garden:
New England
February, 2010
Regional Report

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Plant corn when oak leaves are the size of a squirrel's ear.

Become an Amateur Phenologist

Most gardeners like to observe nature, and it's especially exciting in spring when we see plants and animals return after the long winter. Pity the poor soul who doesn't thrill at the sight of the first crocus, or robin, or bluebird -- what wonders they are missing! As we observe the cycles of growth in our gardens and landscapes we become familiar with seasonal patterns. The study of this relationship between climate and biological phenomena is called phenology. The word translates to "the science of appearances."

The return of migratory birds, the emergence of insects, and the blooming of wildflowers are all examples of phenological events whose timing in spring depends on a variety of factors, including weather and day length.

Aldo Leopold, an internationally respected scientist and conservationist, was an avid phenologist. He kept extensive records of natural seasonal events near his home in Sauk County, Wisconsin. He wrote, "Many of the events of the annual cycle recur year after year in a regular order. A year-to-year record of this order is a record of the rates at which solar energy flows to and through living things. They are the arteries of the land. By tracing their responses to the sun, phenology may eventually shed some light on that ultimate enigma, the land's inner workings."

Phenology isn't just an intellectual endeavor, however. It can be a useful tool in deciding when to plant specific crops and when to expect insects and diseases to make their appearances. Historically, farmers and gardeners were some of the keenest observers. Rather than relying on a calendar, they turned to nature's clues to decide when to plant what.

They knew, for example, that it was time to plant corn when oak leaves were the size of a squirrel's ear. Why? Because no matter what the calendar says, oak leaves that size indicate that the soil has warmed up enough for corn seed to germinate. Sadly, we've lost much of the lore handed down through the generations. But such knowledge just might be coming back into vogue.

The last few years have brought some remarkable weather events -- floods, fires, hurricanes, early and late freezes, and midwinter thaws. Records are being broken across the country for extreme temperatures, rain, and drought. During times like these, averages lose their meaning. When was the last time your actual last spring frost coincided with the official average last frost date?

Weather affects more than our gardens; it also affects the life cycles of many of the organisms in our landscapes. And erratic weather can cause havoc. For example, scientists believe that bird migrations are based in part on day length -- as the days get longer, birds wintering in the south are called to fly north to their summer breeding grounds. The growth of insects and plants, on the other hand, is more closely correlated to air temperature. Suppose early spring temperatures are warmer than normal up north, leading to an earlier emergence of flowers and insects. What happens if these flowers and insects have come and gone by the time the birds who depend on them for food finally arrive?

One of the goals of the USA National Phenology Network (USA-NPN) is to establish a nationwide network of citizen scientists trained in simple, uniform procedures to observe, report, and utilize their data. At the USA-NPN Web site ( you can select a state and view a list of plants for which data is being collected.

By engaging thousands of citizens nationwide in the collection of scientific data, these programs will be able to analyze far more data than would be possible from isolated government and university studies. They'll be able to track short-term weather trends and begin to look at long-term changes in climate. And the information may be useful in analyzing why certain species are on the decline.

Why not put your natural inclination to observe nature to further use and take part in these fascinating studies?

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