Plants confused by balmy temps

  • Article by: MARY JANE SMETANKA , Star Tribune
  • Updated: December 31, 2011 - 5:21 PM

Normally long dead or dormant, some plants hang in as winter struggles to get started

In September, Judy Moran planted pansies by her Minnetonka home for a little fall color.

They're still blooming. Bulbs planted on the south side of her house are poking their noses out of the soil, too.

While it's not unusual for pansies to survive winter under a protective layer of snow, it's odd to see them flowering away on naked ground at this time of year. Moran and other Master Gardeners around the state report that sedums are sprouting, parsley and thyme live on and magnolia buds look suspiciously close to popping.

They're all signs of a peculiarly warm fall, and now winter. While staff at the Minnesota Landscape Arboretum say they're not seeing anything abnormal -- Bachman's CEO Dale Bachman confirmed it by running outside to make sure the crocus weren't sprouting at his company's south Minneapolis headquarters -- strange things are happening in certain places.

"I've been keeping an eye on my magnolia at home," Bachman said. "It's dormant. ... But it's possible, in a microclimate, that we see things we wouldn't normally see at this time of year."

Along the warm south sides of buildings and on sunny slopes, some plants are coming to life. Kathy Zuzek, a University of Minnesota extension educator, said she doesn't doubt reports of magnolias and certain roses that look ready to bloom. Though varieties of those plants have been bred to survive here, she said, their genetic roots lie further south.

Magnolias, redbuds and some types of everblooming roses "are not set up to take Minnesota's environmental cues like the plants that evolved here over millions of years," she said.

Plants native to Minnesota begin slipping into dormancy as day length shrinks. By September, Zuzek said, most native woody plants could survive if the temperature fell to zero.

A second trigger of dropping temperatures sends those natives into full dormancy, from which they usually don't emerge until spring.

Though daytime temperatures have been much warmer than average, most nights have seen freezing temperatures that have held native plants dormant. Zuzek said non-natives may be more confused by the weather's mixed signals.

"I can see some of the repeat blooming roses getting into trouble; they never seem to know when to go dormant," she said. "Redbuds might be a good example, too."

Nothing can be done about sprouting bulbs or perennials. Bulbs are unlikely to totally emerge from the soil, and as long as flower buds remain underground they should bloom normally in spring.

With other perennials, it's not too late to mulch if you can find the material. Even cutting up a Christmas tree and spreading the branches over perennials will help steady soil temperatures, Zuzek said.

She is more worried about the lack of snow than the mild temperatures. In many places, the soil is like dry powder. If homeowners didn't water before the ground froze they may find branches on pines and arbovitaes turning brown by spring.

Dry soil is easily penetrated by frost, and the soil heaving that results from freezing and thawing can kill perennials.

Any snow that fell Saturday night will probably disappear by the end of the week, when daytime temperatures are expected to again reach the 40s. Snow is a great insulator, protecting plants and the ground from extremes. That's one more reason to wish for some white stuff from the sky.

"A snow cover would do some good," Bachman said.

Mary Jane Smetanka • 612-673-7380; Twitter: @smetan

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