Winter has been too bloomin' warm: Some spring plants are flowering

Lexington's mild winter has confused some plants, which are flowering a month early

ctruman@herald-leader.comFebruary 10, 2012 

  • Hardiness-map changes will matter to gardeners

    The federal Agricultural Department released its new zone hardiness map last month, which could affect how gardens are planted nationwide.

    If you're a Kentucky gardener, you probably think you're in Zone 6.

    In the new hardiness map, Fayette County and its surrounding area are zone 6b, meaning the average annual extreme minimum temperature from 1976 to 2005 was minus 5 to 0. In far Western Kentucky, a cluster of counties falls into zone 7a, with temperatures of 0 to 5 being the winter extremes.

    However, Jackson County and about half of Clay County are in zone 6a, with an annual temperature floor of minus 10 to minus 5 — frigid, compared to the rest of the state.

    The same chillier effect goes for a string of counties including parts of Oldham, Trimble, Carroll and Boone. To the east, chunks of Morgan, Elliott and Carter counties also are in 6a.

    When you study your gardening catalogs, dreaming of that swath of summer color that will be the envy of the neighborhood, your zone matters. It also matters to the garden catalog companies, which ship to various areas of the United States according to their zone hardiness. The changes, however, will not be reflected on this year's seed packets.) The National Gardening Association estimates that 82 million Americans do some form of gardening.

    The map had not been updated since 1990. Changes in the new zone hardiness map reflect more advanced mapping capabilities and the effect of climate change.

    To see the map in detail, go to Planthardiness.ars.usda.gov/PHZMWeb. Click on any state to see detailed maps of its hardiness zones.

    CHERYL TRUMAN

The unusually mild winter we've had might have an odd side effect: Spring flowers and spring blooming shrubs are making their appearance earlier than they normally would.

Many daffodils and tulips have pushed through the soil, thinking the spring thaw has begun and it's almost time to bloom. Likewise, forsythia, roses, hydrangea and ornamental trees are blooming or preparing to.

But what happens to them if the temperature suddenly plummets, or at least gets much colder, as is expected this weekend? Will we have a spring without the glory of spring flowers?

Jesse Dahl, horticulturist at The Arboretum on Alumni Drive, Kentucky's state botanical garden, said early blooming plants at the arboretum, such as hellebore, are blooming about a month early.

"We've got one daffodil that is blooming, and it bloomed last year in the middle of March," Dahl said. "For stuff that blooms later in the season, it's still pretty safe."

A dawn viburnum at The Arboretum has been blooming since December:

"It just doesn't know what season it is," Dahl said.

The trouble is, Dahl said, Lexington had a relatively mild winter. Many plants are confused.

"It just hasn't cooled down and stayed cold to put them in dormancy," he said.

For most of the shrubs, more typical February temperatures mean that this year's blossoms might be more restrained or missing. However, such plants are perennials and will be fine.

The Arboretum planted 2,000 bulbs, including 1,500 tulips, for spring display.

"If we get a severe cold snap, they're just gone for the year," Dahl said. "We were expecting spring in March, not in February."

Jamie Dockery, the Fayette County Cooperative Extension Service horticulturist, said there's no black-and-white answer to those questions. Conditions can vary, creating microclimates from house to house, depending on where plants and trees are growing.

Daffodils' comparatively spindly stems might be downed by sudden cold, but the bulb still might flower on the ground. Tulips are more dicey. Because they generally bloom later than daffodils, tulips seem to be hardier than they really are in our climate, where they are often considered an annual that must be planted each fall to bloom the following spring.

In general, Dockery said, "If the bud is still tight, they're probably fine and can take a good bit of up and down. ... But a lot of this depends on how cold it gets how quickly."

The best-case scenario for eager plants is that the temperature goes down gradually over many days. In the worst case, the temperature plummets overnight.

Woody shrubs — such as forsythia and roses — and trees might suffer minor damage by a sudden temperature drop, but over the long term, they probably will be fine. Nonetheless, don't expect a spectacular spring show of yellow forsythia blooms if the temperature continues to yo-yo.

Dockery said the great thing about perennials is that even if they go through a rough patch of weather, they aren't gone for good.

He is not a big fan of trying to cover plants with sheets, because so many home gardeners do it wrong. Covering only the top of the plant — what Dockery calls the "lollipop" look — is not helpful. If you're going to sheet up the yard, drape the sheets so they are in contact with the ground. What you're trying to do is to gain a few degrees of radiant heat from the ground that you can't get from the air.

Speaking of ground, Dockery said that homeowners should avoid walking on their frosty lawns: It breaks grass blades and gives the lawn a ragged look.

"You never want to walk on frozen grass," he said.

Cheryl Truman: (859) 231-3202. Twitter: @CherylTruman

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