University of Vermont Extension
Department of Plant and Soil Science
Spring News
Article
PRUNING
GRAPE VINES
Dr. Leonard
Perry, Extension Professor
University of Vermont
If
you're growing grapes at home, late winter and early spring is the
time for a
major pruning. Not pruning off enough is
one of the biggest mistakes beginning grape growers make. Between
70 and 90 percent of the previous
growth should be removed this time of year, each year. This is
because grape vines, assuming you
have ones hardy for your area, can be quite vigorous, producing
more growth and
fruit than roots can support. Only prune
less if vines aren't vigorous for whatever reason, such as poor
soil, too
little fertilizer, part shade, or poor match for your climate.
Grape
pruning can get rather complex, and is for commercial growers,
varying with
region, training system, even cultivars (cultivated varieties).
But in home gardens grape pruning should be
somewhat simple, especially after you do it a few times and get
the hang of
what to cut. If you're too squeamish
about cutting too much off, do some one day, then come back and do
more the
next, and so on until the vines have enough removed.
Don't worry about pruning just the right way,
there really isn't one, and each vine is different. Also these
are vines not stone sculptures--if
you do make a mistake, the plants will grow out of it.
The
type of pruning will depend on what kind of structure or trellis
you have to
support the vines, and type of vines. The
most common home systems are either one wire strung between posts
about 5 feet off the ground and parallel to it
(the single wire system), or this and one wire half way between it
and the
ground (the two wire system). These may
have other names, depending on if the vines grow up to the wire,
then are
trained only in one direction (single cane) or with canes
branching off along
the wire in opposite directions (bilateral).
So a
bilateral 2-wire system with 4 canes has one in each direction on
the top and
on the lower wires. This is perhaps the
most common home system, often called the 4-cane Kniffen system.
Since the older short stubs near the trunk,
from which canes come each year are called "arms", this may be
seen
too as the 4-arm system. The canes along
the wires are called "cordons", so you may see this called the
4-cordon system.
If just
setting up a trellis and planting grapes, put posts in the ground
to a depth of
2 to 3 feet, every 8 feet along a row.
Posts should be 5 to 6 feet above ground. You'll plant one vine
centered between each
pair of posts. End posts should be
angled outward (about 60 degrees from horizontal) so they don't
sag
inward. Wires should have turnbuckles
(as from hardware stores) on the ends, and on the wires leading to
anchors on
each end. These keep wires taut. On each end, use guy wires from
the slanted
(outward) posts to some form of anchor on or in the ground. This
can be a screw anchor as for trees or
tents, or a buried block.
The
second main factor to consider with pruning is the type of vine,
which leads to
the second type of pruning method. In
the above systems, canes are pruned back to near the trunk each
year, leaving
stubs (the arms) with only 4 or 5 buds on each.
This is called "cane" pruning.
If the canes are left on the wires and not pruned back, but rather
the
fruiting shoots from the past year that have grown off these canes
are cut
back, this is "spur pruning".
It's called this because when you cut back these fruiting shoots
in late
winter leaving only 2 or 3 buds on each, these short stubs on the
canes are
called "spurs."
Once
you cut back all this previous fruiting wood, creating spurs, thin
out the
spurs. There should be on every 6 inches
or so along the cane along the wire.
This keeps too many fruiting shoots from forming the next year,
more
than the plant can support and still make good size clusters of
grapes.
Cane
pruning is used for most grapes. Spur pruning is mainly used on
the vigorous southern
muscadine grapes (where they're hardy in mild climates), as well
as some European
ones. Spur pruning typically only
utilizes one top wire.
Once
your early spring pruning is done, there is one more time you'll
need to
prune. Actually it is a thinning process
once the grapes start forming in summer.
When fruit are rather small, only 1/8-inch or so across, remove
whole
clusters leaving only one or two bunches of grapes on each new
shoot. This is all the leaves on the plant can
support in order to grow grapes with the size and flavor to which
we're
accustomed. You should remove any
clusters that start forming the first two years after planting so
the plant can
direct all its energy into growth.
Return to
Perry's Perennial
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