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Why are there flowers blooming in December? 'Plants respond to weather'

A few flowers on Mexican orange are not unusual this time of year, but entire shrubs in bloom isn’t a normal circumstance. Photo by Neil Bell.

CORVALLIS, Ore. – Winter has yet to start, but it looks like spring has sprung in parts of the Willamette Valley.

A wetter than usual October ...

... followed by a warmer than usual November ...

... appears to have confused flowering plants in the Willamette Valley.

“Plants respond to weather,” said Wilbur Bluhm, a retired Oregon State University Extension Service horticulturist. “If we get cold weather, they slow down. If we get warm weather, it can hasten bloom.”

Another factor: the southern Willamette Valley hasn't seen freezing temperatures yet. The last time the mercury dipped below 32 in Eugene was February 23.

“It usually would have hit 32 a month ago and we haven’t come close,” said Kathie Dello, associate director of OSU’s Oregon Climate Change Research Institute.

Dello said the Willamette Valley is on track for the latest first frost date in history.

The record was set in 1998 when it came on Dec. 9.

The temperature is forecast to dip into the 30s next week with freezing temperatures possible.

“It’s been warm,” Dello said. “We’re looking at one of the warmest years in the history of Oregon.”

As a result, impatiens, begonias and geraniums are still in bloom.

Many other annuals and perennials are still upright.

And while it’s not uncommon to see rhododendrons, azaleas and Mexican orange put out a few flowers in fall, some plants appear close to full bloom.

Neil Bell, an Extension horticulturist, saw several Mexican orange covered in flowers Nov. 21 in Dallas.

On the Oregon State campus, the ceanothus - a spring-blooming shrub not known for repeat flowering - is putting on a show now.

“I saw it from 50 feet away,” Bell said. “I thought, ‘Wait a minute, that looks really blue.’ Then I realized it was a ceanothus hedge. It was blooming like crazy.”

Elsewhere, Mahonia "Charity" is sending up bright yellow blooms a month early.

And the sure sign of spring - daffodils – are appearing in some people's yards and gardens.

So will this affect the plants' normal cycles?

Bell said that's hard to know, but it’s a possibility they'll show fewer spring blooms.

Bluhm has spent more than 50 years observing plants and animals change with the seasons.

“Very few people have the data to turn to, so consequently it may seem early or late,” he said. “Recall is the best they have to use to pass judgement on those situations. When I say that I’m not being critical at all. Because if I didn’t have the info I have, I might have the same idea they do.”

This year, however, if you think the flowers are blooming late, he said - you're right.

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