Chronicle Online e-News
Sudden, deep cold snap could be lethal to some
Finger Lakes grape varieties, Cornell experts say
http://www.news.cornell.edu/stories/Jan07/warm.temps.gra
pes.html
Jan. 16, 2007
By Franklin Crawford
fac10@cornell.edu
Finger Lakes sybarites love to romance their
regional vintages, but the reality is that grape
growing is crop farming, and crop farming is
largely weather dependent. With a mild central
New York winter suddenly returning to normal or
below-normal temperatures, area grape growers
have reason to be worried for their crops.
Because of water retention at warmer temperatures
followed by a sudden freeze, this year's
harvests, from Chardonnays to Concords, are
threatened by damage to buds that will produce
this summer's grapes, say experts at Cornell's
New York State Agricultural Experiment Station in
Geneva, who are keeping a close watch on their
vineyards.
"The main concern is with buds freezing," said
Tim Martinson, senior extension associate at
Geneva. Mild weather has caused grapevines to
retain water and buds are more vulnerable to
freeze-kill at 4 degrees higher than is typical.
"The plants need to gradually lose water and
acclimate. And with warm, moist conditions
followed by unseasonably cold temperatures, that
doesn't happen."
A sudden deep freeze could cause cells to burst
in the vines' trunks and buds. In 2004-05, for
example, temperatures suddenly plummeting to
minus 10 degrees Fahrenheit destroyed 75 percent
of such cold-sensitive grape crops as Riesling,
Chardonnay and Pinot Noir, as well as many stone
fruits.
A sudden cold front this week is sending
overnight temperatures down into single digits at
least once, with daily temperatures in the 30s
and lows averaging about 14 degrees, said Mark
Wysocki, state climatologist with Cornell's
Department of Earth and Atmospheric Sciences.
There will be a warming trend Wednesday and then
unseasonably to seasonably cold temperatures
Friday, Saturday and Sunday, he said.
"We're in for a bumpy ride for at least the next week or longer," Wysocki said.
That's not welcome news for area grape growers.
While all varieties can be damaged by sudden
freezing, such varieties as Merlot, Pinot Gris,
Cabernet Sauvignon, Pinot Noir and Gew�rztraminer
are particularly susceptible, said Martin
Goffinet (GOF-fin-nay), senior research associate
at the Geneva station. The vinifera varieties
(those that originated in Europe) and many hybrid
varieties (many developed at Cornell) also are
particularly vulnerable to winter cold snaps
because they tend to acclimatize slowly, he said.
Bud growth actually begins the year before the
grape emerges, Goffinet explained, so the
following summer's embryonic buds are already
growing while the vine producing the current
season's harvest is in bloom. Under normal
conditions, buds acclimatize to gradually cooling
temperatures throughout a seasonable winter.
American varieties, including Concord, Delaware
and Catawba, acclimatize quickly but are
vulnerable to spring frosts because they come out
of winter dormancy earlier.
"Typically the first week of February is the
coldest week with temperatures dipping down to
zero or minus 5 Fahrenheit," Goffinet said. "In a
typical year, vines seem to do okay; they've had
lots of prep, and the buds are dry. We are
concerned right now but we haven't yet had
temperatures that can kill the vine. But if the
trunks fill up with water, and there's a sudden
hard freeze, they can actually split."
The most susceptible grape varieties, he said,
will need about one to two weeks of cold (but not
bud-killing cold) temperatures to regain the
winter hardiness they would typically have at
this time of year. Goffinet also said stone
fruits -- apricot, peaches and sweet cherries in
particular -- are also susceptible to warmer
temperatures, and any precipitous drops in
temperature "are going to be problematic for next
season's crop."
"Between the poor fall ripening and warm winter
temperatures, we're hoping we don't see any
below-zero conditions any time soon," added
Geneva researcher Steve Luce, who conducted
freezing experiments on buds Jan. 3. "Sometimes
all it takes is a one deep freezing event to
cause damage."
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