University of Vermont Extension
Department of Plant and Soil Science
Anytime News
Article
NORTHERN GRAPE GROWING
Dr.
Leonard Perry, Extension Professor
University of Vermont
Growing
grapes in cold, northern climates isn't difficult if you've chosen
hardy
varieties, a good site, and follow some cultural basics. This
includes knowing the basics of pruning
grape vines.
There
are three basic groups of grape varieties.
European or vinifera varieties include such popular names as Cabernet
and Riesling, and aren't hardy below about -10 degrees F (USDA zone
6). American or labrusca varieties such as Concord and Catawba
are
hardy to -15F or colder. Some of the
most hardy, developed in Minnesota
and often known as Swenson varieties after their breeder, include names
such as
Frontenac and Prairie Star. Hybrids of
the American and European varieties have moderate hardiness from -10 to
-15F.
The
best site is one with full sun, good air drainage, and soil that isn't
too wet
or dry. Grapes do tolerate a range of
soil types and soil drainage. Avoid
north-facing slopes and low areas that remain cooler and delay fruit
ripening. Choosing a warm microclimate,
such as near a building or a south-facing slope, you may be able to
grow
varieties not listed for your hardiness zone.
Once
a site is chosen, erect a trellis or arbor.
A split rail fence works well too, and is attractive. Grapes grow
on most any structure, including
trees. They can cover evergreen trees in
a few seasons, killing branches. The
goal is to use pruning and training to keep grape vines manageable and
productive. A common trellis system is known as the "four-arm Kniffen
system", and consists of two wires at three and
six feet high, strung tightly between wooden posts 24 feet apart.
Training comments refer to this system, but
the principles apply to others.
Whatever
system and structure you use for training, keep in mind three main
principles:
--Vines should have only one or two layers of leaves
during a season.
--You should prune up to 90 percent of new growth off
during the dormant season in late winter or early spring.
--Vines will bear fruit on current-season shoots that
grew from buds on side branches from previous year growth.
Plants
roots in spring, as soon as the soil can be worked, spacing plants
eight feet
apart. Make holes large enough for the
roots, trimming excessively long ones.
Water well. Don't fertilizer the first year. In subsequent years
use two ounces per vine
of 10-10-10 or the equivalent in year two, increasing to 16 ounces per
vine in
year five and after.
Remove
all but the best single cane, and tie it to the trellis bottom wire or
a
stake. They need support to grow
straight. Buds will grow in a few weeks. As the
single cane grows, remove all but the
strongest shoots, and flower clusters as well.
Your goal is to have one single cane reach the top wire of a trellis
the
first year, or if not then the following spring.
Early
in the second year, tie the cane to the top trellis wire, and cut it
off just
above the wire. Leave four to six buds
near each wire, then remove any others as well as any flower
clusters. Allow these buds to grow into shoots the
second year.
Early
in the third year, while vines are still dormant, prune them
hard. Select four healthy canes or side shoots near
each wire to keep, then remove the rest.
Train one cane on each wire going in each direction, so two on the
lower
wire, two on the upper. These are the
four "arms" of the Kniffen system.
Allow these four arms to fruit up to the sixth bud along the
stems. Cut the
remaining four canes back to a couple buds. These are the
"renewal spurs" that
will produce fruiting canes next season.
In
subsequent years, remove the fruiting canes from the previous
year. As the shoots grow from the renewal spurs,
train two to each wire, then prune after it has produced ten
buds. You should have two shoots left on each wire,
which you can prune back to two buds for next year's renewal
spurs. The whole point in this pruning is to have
enough buds for shoots to produce fruit, but not too many which will
result in
poor quality and vine growth.
Often
the most productive buds, then shoots, are at the top of the trellis
where the
previous season buds were exposed to the most light. Ideally the
distance between leaves should be
about six inches, with the cane diameter between leaves one-quarter
inch or
more.
For
arbors, prune annually, but allow the trunk to grow longer, and keep
more
fruiting canes and spurs. Train short,
permanent arms from the main trunks so leaves will cover the arbor.
Harvest
grapes when fully ripe, since their sugar content does not increase
once they
are picked. The peak is usually about
one week after grapes have good size and color.
After this the quality goes down rapidly. Yields will vary with
season, site, vine
vigor, and culture, but by the third year might be five to ten pounds
of fruit
per vine. Remove bad grapes from
clusters before storing the good ones in refrigeration.
Controlling
weeds is essential for best fruit quality and yields. This is
best done with frequent, shallow
cultivation around vines. Organic
mulches, such as bark or rotted sawdust, will help control weeds and
conserve
moisture. These mulches may keep soils
cooler, delaying ripening. Also they may
harbor rodents in winter that can damage vines.
Good
air circulation, pruning infected shoots, and using less susceptible
cultivars
are non-chemical solutions for diseases. Diseases to get familiar
with, and watch for,
include powdery mildew, black rot, downy mildew, and botrytis.
Insects
to learn about and watch for include Japanese beetles, grape berry
moth, grape cane
girdler, and grape leafhoppers. Birds
and
raccoons can be problems with grapes, especially the
larger seedless varieties.
Learn
more on potential grape insect pests and diseases in Cornell leaflets
online
(nysipm.cornell.edu/factsheets/grapes).
Return to
Perry's Perennial
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