Chronicle Online e-News
Come spring, expect fewer blooms, due to mild early winter, say
Cornell horticulturists
http://www.news.cornell.edu/stories/Jan07/warm.winte
r.spring.cc.html
Jan. 29, 2007
By Craig Cramer
cdc25@cornell.edu
With record warmth throughout the Northeast in December and early
January, gardeners and commercial growers are asking: "Will the warm
weather wither my plants?"
The quick answer is: It depends. But expect fewer blooms on flowering
trees and shrubs in the spring.
In addition to the particular plants involved and your location, how
your plants fare depends on how quickly the cold temperatures
returned, how cold it gets, and other environmental factors.
"I don't think we've seen the extremes yet that would cause a lot of
long-term damage to trees and shrubs," says George Good, Cornell
professor of horticulture and a landscape plant expert.
A sudden drop to subzero temperatures following the warm weather in
early January would have severely stressed many plants, says Good.
But most plants should acclimate well since the return to more-normal
winter temperatures experienced in much of the Northeast has been
gradual.
"Some flower buds will be killed. So we may see fewer blooms on
flowering trees and shrubs this spring," predicts Good. That has
commercial fruit growers concerned, as they will harvest less fruit
if too many flower buds die. But for most of us, it just means we'll
see fewer flowers.
To reduce potential problems, Cornell horticulturists suggest the following:
Lawns: Although the unseasonable warmth encouraged root growth and
young seedlings, if temperatures drop too fast, lush top-growth may
be more prone to freezing damage. So, avoid walking on lawns as much
as possible until the soil dries out and grass starts growing again
in spring, says Cornell horticulturist Marty Petrovic.
If temperatures fluctuate a lot, it could kill grasses, says turf
specialist Frank Rossi. Note low-lying areas where water collects and
ice forms, and plan to improve drainage before next winter. Replant
bare spots this spring before weeds have a chance to move in. For
directions, see <http://www.gardening.cornell.edu/lawn>.
Trees and shrubs: A warm winter may prompt some ornamentals to flower
prematurely, says Nina Bassuk, woody plant specialist and director of
the Urban Horticulture Institute. "We'll lose some of those flowers
for this season, but the long-term health of most [of these] plants
probably won't be affected," she says.
Berries: If you mulched your strawberry patch, the plants should be
fine, says berry specialist Marvin Pritts. Blueberries are slow to
respond to warming temperatures, so he's not worried about them
flowering prematurely. A rapid chill could freeze some of the
blackberries and raspberry buds, but even if the entire cane dies,
healthy new canes will emerge in spring; even if this summer's berry
crop is lost, 2008's should be fine, says Pritts.
Perennial flowers: Most bulbs and perennial flowers should come
through the winter just fine, says Bill Miller, director of Cornell's
Flower Bulb Research Program, even if they started to flower. "The
flowers that opened will probably survive, especially if we get some
snow cover before really cold weather returns," says Miller.
It's common for the leaves of some bulbs, such as grape hyacinth and
early daffodils, to emerge in fall or winter. The leaves may suffer
some damage. But the flower buds are still deep underground and well
protected from cold weather.
Vegetable gardens: The warm weather in December was great if cover
crops or such cool-season greens as kale were planted, says Betsy
Ingall, a technician who manages vegetable research plots at
Cornell's Thompson Research Farm in Freeville, N.Y. But vegetable
gardeners and commercial growers should be on the lookout this season
for pests they may not have had to deal with following colder
winters. When planning this year's vegetable plantings, consider
testing some new pest- and disease-resistant varieties that also
might perform better during hot seasons, she suggests.
====
Cornell horticulturist warns that warming trend could change what
plants to grow -- and what pests will attack
In the future, chances are good we will see more warm winters like
the one that, before early January, at least, had the Northeast
basking in unseasonably high temperatures, says David Wolfe, Cornell
professor of horticulture.
"We may still have some very cold winters," says Wolfe. "But all the
climate models point to a warming trend, and nature is already
responding to the warmer conditions."
Wolfe, who studies how climate change -- caused in part by increasing
carbon dioxide levels in the atmosphere -- is affecting agriculture
in the Northeast, says there is mounting evidence that the climate is
warming. In the Northeast, he says, lilacs are blooming four days
earlier on average than they did in the 1960s. Warmer temperatures
are also affecting such cultivated crops as grapes (blooming six days
earlier) and apples (blooming eight days earlier).
Studying long-term climate trends can't pinpoint what the weather
will be like next week or next winter. But Wolfe says that warmer
winters could allow gardeners to grow some plants that previously
could only grow in milder climes. And the wine-grape industry, which
relies on varieties that are only marginally cold-hardy in upstate
New York, may benefit from warmer winters.
On the other hand, aggressive weeds and invasive plants would also
move north. Studies show those species are better equipped than crops
to take advantage of the increasing carbon dioxide levels in the
atmosphere that are driving warming, notes Wolfe.
Pests and diseases that were held in check by the cold could become
more of a problem. Life cycles of beneficial insects might get out of
sync with the pests they help control.
Natural ecosystems would shift north, with oak-pine forests replacing
maple-beech-birch forests in some places, for example, Wolfe notes.
Less reliable winter snow cover could hurt overwintering of some
perennial crops and flowers, and hotter summers would cause heat
stress even in such warm-season crops as tomatoes.
It's uncertain, says Wolfe, if weather would become more variable
along with higher temperatures. Most models, he observed, predict
fewer but more concentrated precipitation events, causing more
flooding and drought.
For gardeners, adapting to a changing climate may be as simple
finding better-adapted tomato varieties or other plants to grow. But
for commercial growers, changes would likely be more involved.
"Everyone is going to have to invest some to respond to climate
changes," says Wolfe.
For more information, see "Climate Change and Northeast Agriculture"
at <http://www.climateandfarming.org>.
====
Craig Cramer is an extension support specialist in the Department of
Horticulture.
--
Chronicle Online
312 College Ave.
Ithaca, NY 14850
607.255.4206
cunews@cornell.edu
http://www.news.cornell.edu
