Report: Climate Change Causes Plants to Flower Historically Early

Temperature increases have caused flowers to bloom up to a month earlier than normal.

Snow covered daffodils are pictured on March 24, 2008 in Duesseldorf, Germany.

Dozens of flowering plants have gradually begun blooming earlier as average temperatures rise.

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Spring has, well, sprung, earlier than ever in the past few years. A new study suggests global warming is causing dozens of flower species to bloom more than a month earlier than they did in the past.

According to the study, published in the journal PLOS ONE Wednesday, dozens of flowering plants in Massachusetts and Wisconsin have gradually begun blooming earlier as average temperatures creep up. For example, the highbush blueberry plant flowered April 1, 2012—in the 1850s that plant normally flowered in mid May.

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Elizabeth Ellwood, of Boston University's department of biology, says the development "speaks to the big picture of climate change." Her team found a direct correlation between higher average spring temperatures and earlier flower blooming. For every 1 degree C increase in average springtime temperature, plants bloomed about 3.2 days earlier.

"The correlation is so strong that there's no doubt it's the strongest factor" controlling plants' blooming schedules, she says.

For now, the change simply means certain parts of the country could see longer growing seasons, she says. But if the trend continues, some plants might not be able to flower at all.

"It'll be species-specific. Some will begin to flower earlier, but others won't have enough of a cooling during the winter to flower at all," she says. "At some point, these temperate species will reach the point where they can't keep up."

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Ellwood and her team used historical data from authors Henry David Thoreau in Massachusetts and Aldo Leopold in Wisconsin, which she says are some of the earliest records of plant blooming in the United States.

"Their works are essential to our understanding of things — we now have insight to how things were 160 years ago which gives us a chance to compare it to today," Ellwood says.

A year ago, the U.S. Department of Agriculture released its first new Plant Hardiness Zone Map in 22 years due to global warming. When that map was released, many farmers and gardening enthusiasts noticed they were able to grow warm-weather plants further north than they used to be able to, and other plants were blooming earlier than expected.

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