Chicago Sun-Times
Stray Casts will intelligently report and observe, hopefully with a touch of wit, on daily occurrences, reports and releases related to Chicago-area outdoors from bucks to bass to birds to bugs

Chicago outdoors: Banner year for mast?

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The Morton Arboretum trumpets a ``a mast year.''


It makes sense and I enjoy their breakdown of why. I artfully arranged the photo above from some bounty from a neighbor's sidewalk. (BTW, not sure if I envy the lead sentence of the release or want to poke out my eye after reading, probably lean toward envy.)


"Mast Year" Occurs Periodically

LISLE, IL (September 15, 2010) - The nuts really bolted this year.

The Morton Arboretum experts say that oak trees dropped an exceptionally large number of acorns: the nuts (also called fruits) of oaks. "This is one of the heaviest years I've seen for acorns, not just in the Chicago region, but in other states as well," says Kris Bachtell, Vice President of Collections and Facilities. Bur and red oak species yielded a particularly large number of acorns.

A year of such heavy production, called a mast year, is a natural, cyclical process that apparently helps to guarantee a species' survival, and does not harm the trees.

Each fall, tree roots store energy that's used the following spring to expand buds, and create twigs and leaves. A mast year does not leave oaks with a large energy deficit or otherwise harm the trees, according to Dr. Gary Watson, Arboretum Senior Scientist and Head of Research.

"Trees maintain a healthy balance of using energy to create fruits and for other functions," Watson says, noting also that oak species survive hundreds of millions of years despite experiencing mast years.

Indeed, the periodic upswing in acorn production may be necessary for oaks' survival. "Trees evolved to have mast years, triggered to occur within a species by climatic variables," says Marlin Bowles, Arboretum Conservation Biologist.

Experts theorize that if oaks produced the same number of acorns every year, predators would eventually become so numerous and consume so many acorns that there would not be enough to feed the predators and grow a new generation of seedlings. During mast years, predators are "over saturated," Bowles says, providing enough acorns for the predators and for seedling production.

Bowles recalled the last mast year in 2003 at the Arboretum's East Woods left oak seedlings popping up everywhere the following year, including along the Arboretum's wood-chipped trails. Researchers recorded 80 seedlings in just one, ten-square-meter plot. They also noted an average of 13.5 seedlings per 10 square meters in areas that were burned for woodland area management, and 8 seedlings per 10 square meters in unburned areas.

What's behind the oak trees raining down so many acorns? Bachtell says there could be many reasons, but he points to the warm, dry weather we had in April and May, saying it was "favorable for pollination." The early spring weather brought prime conditions for tree flowers to flourish and for wind to carry pollen to the flowers.

As an example, data gathered at the Arboretum, which is the National Weather Service Lisle Station, showed that April of this year averaged 10 degrees warmer than April of 2009; and May was three degrees warmer on average. Additionally, frequent rainfall in summer allowed the seeds to develop fully within the flowers.

What can homeowners do about the abundant acorns? Either leave them for the animals, or "sweep them up," Bachtell says, adding that they will not harm grass or other plants.

The Morton Arboretum is a world-renowned leader in tree science and education, working to save and plant trees. The 1,700-acre outdoor museum features magnificent collections of 4,117 kinds of trees, shrubs, and other plants from around the world. The Arboretum's beautiful natural landscapes, gardens, research and education programs, and year-round family activities support its mission - the planting and conservation of trees and other plants for a greener, healthier, and more beautiful world. Conveniently located at I-88 and Rte. 53 in Lisle, Illinois, the Arboretum is open 7 days a week, 365 days a year, from 7 a.m. Central Time until sunset. The Children's Garden is open from 9:30 a.m. to 5 p.m., March through October, and 9:30 a.m. to 4 p.m., November through February. Visit Press Room at, call to learn more.

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Can't say I've ever thought of squirrels as predators before.

Jim, I loved it, never heard it before, but loved it. Having squirrels described as predators might have been my favorite part of the release. I've called them far worse, at least the ones in my backyard.

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This page contains a single entry by Dale Bowman published on September 16, 2010 9:40 AM.

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