Grape Overview
INTRODUCTION:
Grapes are welcome summer treats that can be eaten fresh, processed
into jellies, jams, juice or even fermented into wine. Grapes are adapted
to many soil types, and can be quite long-lived. There are basically
two kinds of grapes grown in North Carolina, bunch grapes and muscadine.
Bunch grapes produce berries in large clusters, and grow best in the
mountains and piedmont areas. In coastal plain areas, Pierce's disease
kills or shortens the life expectancy of many popular bunch grapes.
Muscadine grapes, exemplified by the Scuppernong variety and noted for
having smaller clusters, are not affected by this disease. In these
areas the kinds of grapes that may be expected to give the best results
are muscadine (see Muscadine Grapes in the Home Garden - Hort. Leaflet
No. 8203).
Your success with bunch grapes will depend upon the attention you give
to all phases of production -- including variety selection, soil management,
fertilization, training, pruning, and pest control. This leaflet presents
detailed suggestions for the establishment and care of bunch grapes.
VARIETY SELECTION:
The choice of variety depends on a number of factors including its
adaptation to your area and the type(s) of grape you prefer. There are
seedless table varieties, native Fox-type table grapes such as Concord,
muscats and many wine varieties. Newer hybrid bunch varieties resulting
from crosses of European vinifera (the old-world grape) with native
American varieties are known as French-American hybrids. Both vinifera
and French-American hybrids are used primarily for winemaking purposes.
However, vinifera type grapes are more difficult to grow and require
regular chemical sprays throughout the growing season to control diseases.
Vinifera are easily injured by fluctuating winter temperatures and typically
sustain greater losses to spring frost events than French-American hybrids.
Vinifera should be grown on a rootstock (Couderc 3306, 3309, or SO4).
The bunch grapes listed in Table 1 are the most suitable for growing
in piedmont and western North Carolina. Six grapevines should furnish
enough fruit for most families. A mature vine can yield 10 pounds or
more of fresh fruit. Early season table grapes will begin ripening in
mid-summer, while a number of the wine varieties do not begin to ripen
until late summer. All bunch grapes are self-fertile and may be planted
alone or with other varieties.
SOIL AND SITE:
Good air circulation, sun exposure and a soil that is well drained
are desirable for quality crops of grapes. Air circulation is best if
the location has a gentle slope; avoid low frosty pockets. Plant the
vines away from trees so that they will receive full sunshine. Grapes
are not as particular to soils as other fruit crops; as long as the
soil is best; rich soils stimulate excessive vine growth at the expense
of fruit quality. Grapes require a soil pH of 5.5 to 7.0.
TABLE 1. BUNCH GRAPES
VARIETY SEASON COLOR SIZE USE REMARKS
Alwood E. Mid Purple Med FF,J Resembles Concord
Catawba Late Red Med FF,J,W All purpose grape
Cabernet-
Sauvignon V. Late Black Sm W Vinifera, excellent
Chambourcin Late Purple Med W French hybrid, red wine
Chardonnay Late White Sm W Vinifera, excellent wine
Concord E. Mid Black Med FF,J Not recommended in piedmont
Delaware Mid Red Sm FF,J,W Good wine or table grapes
Fredonia E. Mid Purple Lge FF,J Heavy producer
Himrod V. Early White Sm-Med FF Seedless, disease susceptible
Lakemont E. Mid White Sm-Med FF Seedless, good quality
Leon-Millot Late Black Sm W French hybrid, red wine
Moored Early Red Med-Lge FF Fruity, productive
Niagara Mid White Med FF,J Popular, fruit, hardy
Seyval Late White Sm-Med W French hybrid, good wine
Suffolk Red E. Mid Red Med FF Seedless, good quality
Venus Mid Black Med-Lge FF Seedless, avoid overcropping
*Designations used: FF = fresh fruit; J = juice; W = wine
PLANTING:
Plant grapevines in late winter and early spring. Vigorous one-year-old
plants are best. Planting will be easier if the soil is spaded or tilled
beforehand. Bunch grape roots rapidly grow out several feet in the first
two years, so working compost or fertilizer into the planting hole will
be of little value. Open a hole large enough to let the roots spread
out naturally (root pruning is not recommended except to remove damaged
roots). Plant the vines the same depth or slightly deeper than they
grew in the nursery. Keep the topsoil separate to place over and around
the roots. Be sure not to place fresh manure or fertilizer in the hole.
Tamp the soil firmly around the roots, and water if dry. After setting
the vine, prune it to one stem and cut this stem back to two or three
buds.
TRAINING AND PRUNING:
To simplify installation and avoid damage to young vines, build and
set the trellis system before the vines are planted. Use wood treated
to resist decay or a durable type of wood such as cedar or locust. Construct
the trellis, setting the line posts 20 feet apart down the row. Brace
the end posts.
During the first season, the primary objective for grapevine growth
is development of a healthy root system and straight trunk. After setting
the vine, prune it to one stem and cut this stem back to two or three
buds. When new growth begins and the first shoots from the two-bud cane
reach 6 to 10 inches in length, select the most vigorous and prune away
the others. Tie the shoot gently to the training stake several times
during the first season. Pinch lateral shoots back to the leaf growing
from the main shoot. This allows the main shoot to grow more rapidly,
possibly saving as much as a year in establishing a healthy vine.
MID-TRELLIS CORDON SYSTEM (for
use with French hybrid vines such as Seyval and vinifera vines such
as Chardonnay and Cabernet Sauvignon). Allow the main shoot to grow
until it reaches 3 feet. Tie it there, pinch off the tip, and allow
several of the lateral shoots to grow. Begin training in the second
year by evaluating the extent of growth achieved during the first year.
If no cane has reached the first wire, remove all but one cane. Prune
this cane back to two buds and treat it as a new vine.
In the winter following the first season of growth, remove all but
a few good canes the diameter of a pencil. No added training is necessary,
but it is vital to remove flower clusters in the second growing season.
Vines that grew extensively in the first year will likely have one or
more canes suitable for retention as a trunk. If a cane is long enough
to reach the lowest trellis wire and is of adequate diameter (approximately
1/4 inch), retain the cane as a trunk. The distal (tip) portion of such
canes can be trained horizontally along the training wire to serve as
the basis for a cordon.
Cordon establishment begins in the second season of growth and should
continue over a two-year period for best results. To establish a 3-foot-long
cordon, begin with an 18-inch cane (or trunk extension) in the second
year, and complete the cordon in the third year with another 18-inch
cane from the distal end of the short cordon. Canes that are used to
establish the cordons should be wrapped loosely around the trellis wire
and tied securely at the end with wire to prevent the cordon from rotating
or falling from the wire.
During the second growing season, shoots that develop below the lowest
trellis wire should be pruned to one or two near the graft union. Retain
10 or more shoots that develop on the cordon in the second year.
In the third year the cordon system should be completed. For the trellis
mid-wire cordon, canes that rise from the upper side of the cordon arms
should be pruned to one- or two-node spurs. These spurs should be 4
to 6 inches apart. Develop a second trunk and cordon from a cane that
originates near the graft union. Keep a small crop of fruit (for example,
one cluster for every two shoots) on vines that had at least 1 pound
of cane prunings from the second-year growth. Tie shoots to wires as
necessary during the growing season. Treat weak vines as second-year
vines and remove all crop.
Cordons may be either unilateral or bilateral; in either case, cordons
should ultimately span the distance between two adjacent vines in a
row.
HIGH-TRELLIS CORDON SYSTEM(for
use with American bunch grapes and Muscadine).
The initial training of the trunk is the same as used with the midwire
trellis system, but in this system cordons are trained along the TOP
wire of the trellis. Spurs (short canes) are retained on the LOWER sides
of the cordons to promote downward growth in American bunch varieties.
The vine must be pruned every year to avoid alternate-year bearing
and to make harvesting easier. Pruning mature vines consists of three
operations. The first step is pruning last season's growth. In the dormant
season, prune back all canes that grew during the previous summer to
4 or 5 inches in length. Leave the remaining spurs at a 6-inch spacing
on young vines. As the vines age, they will develop clusters of spurs.
These spurs must be thinned after the third season to force new spur
growth. This process also minimizes the labor necessary for cane tying
and keeps fruit and renewal regions at a uniform height, facilitating
harvesting and pruning. The second step is to remove suckers or shoots
growing from the trunk and any damaged arms. A new cane must be trained
(from the renewal canes at graft union height) to replace the removed
arm. As the third step, remove all tendrils that attach themselves to
the trunk or fruiting arm of the vine.
Overcropping will greatly reduce fruit quality. Some cluster thinning
in years of heavy fruit set (thinning to one cluster per shoot) is the
simplest way to ensure that those remaining will develop into larger,
more fully ripened clusters. A good rule of thumb for mature vines is
to allow no more than two clusters per shoot. Excess clusters should
be removed before bloom (early May in the piedmont, late May in the
mountains).
FERTILIZATION:
Proper fertilization is essential to high yields and quality. Before
planting vines, broadcast and work fertilizer and lime into the soil
as indicated by the soil test (usually about 2 pounds of fertilizer
and 5 pounds of dolomitic limestone per 100 square feet).
After setting the vines and just before growth starts, apply 1/2 cup
(1/4 pound) of 10-10-10 fertilizer in a 20-inch circle around each vine.
Repeat monthly until July 15th. In the second year, double the first
year amounts but follow the same schedule. For bearing vines, scatter
1 to 2 pounds of 10-10-10 fertilizer per plant over the area. Repeat
with 1 pound per vine in mid-June.
For at least the first two years, keep an area 1 to 2 feet in diameter
around each vine free of weeds by hoeing, hand cultivation, or mulching.
Black plastic is a satisfactory mulch material, but it does not add
to the humus content of the soil. DO NOT USE A COMBINATION FERTILIZER
AND WEED KILLER on lawn areas near grape vines; the weed killer may
be absorbed by the grape roots and injure the vine.
FIRST YEAR - after setting and just before growth starts, apply 1/2
cup (1/4 pound) 10-10-10 in a 20-inch circle around each vine. Repeat
monthly until mid-July. SECOND YEAR - double first year amounts. Follow
same schedule as for first year. BEARING - in March apply 2 pounds 10-10-10
fertilizer per plant, scattered over the area beneath the vine. Repeat
with 2 pounds per vine after fruit sets.
CULTIVATION:
For at least the first 2 years, an area 1 to 2 feet around each vine
should be kept free of weeds by hoeing, or with a heavy mulch of grass
clippings (4 to 6 inches deep). Black plastic is a satisfactory mulch
material, but it does not add to the humus content of the soil. Once
established, the vine will shade out some weed growth. Recommended chemical
herbicides may also be used for weed control in grapes, but mulching
is the preferred management practice. Certain types of herbicides should
not be used near grapes as they are very sensitive (e.g. terbacil, 2,4-D).
Do not use the combination of fertilizer plus weed killer on lawn areas
near a grape vine; the weed killer may be picked up by the grape roots,
and cause vine injury.
CLUSTER THINNING:
Overcropping will greatly lower fruit quality and vine vigor. It is
better, especially on young vines, to do some cluster thinning in years
of heavy fruit set. Thinning to one cluster per shoot (a single shoot
may carry three or four clusters), is the simplest way to ensure that
those remaining will develop into larger, more fully ripened clusters.
With mature vines a good rule of thumb is not to allow them to develop
more than two clusters per shoot. Excess clusters should be removed
prior to bloom (Piedmont - early May; WNC - late May).
HARVEST:
An acceptable taste is the main criterion for table use. On a vine
that is not overcropped, the berries of black varieties lose their red
color and white varieties will change from green to golden yellow. Ripe
berries will soften and seeds become brown. Determining the harvest
of wine grapes requires either experience or a means of measuring both
sugar and acid content.
INSECTS AND DISEASES:
Bunch grapes require frequent and thorough spraying to avoid diseases
and insects. Current recommended spray programs are available through
your local Cooperative Extension agent or the Plant Pathology and Entomology
Departments, N.C. State University, Raleigh, N.C.
Published by North Carolina Cooperative Extension Service http://www.ces.ncsu.edu
Harvesting Grapes
One of the toughest things about growing your own grapes is beating
the birds to the harvest! Could it be that the birds know something
we don't? Netting can be placed over a grape arbor to keep the birds
away from the fruits. But don't be too hasty in cutting the fruits to
one-up the birds. Make sure your grapes are ripe before you harvest.
Although color change is important in determining when to harvest grapes,
it should not be the only consideration. Most berries change from green
to blue, red or white (depending on the cultivar) as they approach maturity.
But most grape cultivars color up long before they flavor up. When fully
ripe, the natural bloom or whitish coating on the berries should become
more noticeable. The color of the seeds changes from green to brown.
One of the other factors to consider in determining harvest time is
the size and firmness of the berry. It's helpful to be familiar with
your cultivar's individual characteristics, but most grapes should become
slightly less firm to the touch.
The best telltale sign of ripeness is the grape's sweetness, and, of
course, the most reliable method for homeowners to test this is to taste
them! Unlike some other fruits, once the grapes are cut from the vine,
they will not ripen any further. So, be sure the grapes are ready before
you harvest.
Grapes don't require direct sunlight on the fruits to ripen and develop
good color. Rather, it is the amount of light that reaches the plant's
leaves that governs the quality of the fruit. The leaves manufacture
the sugars that are then translocated to the fruit. To protect your
ripening crop from hungry birds, you can place bags over individual
fruit clusters beginning when the grapes are about half grown. Use a
sturdy brown paper-type bag that will allow enough room for the bunch
to develop, and tie securely to the grape cane. Bagging also might help
protect the fruits from inclement weather, as excessive rains close
to harvest time can cause the grape's skins to split. Of course, bagging
is not very practical for larger plantings, in which case netting is
the best alternative.
Some grape-growers have experienced uneven ripening this year, particularly
with their concord grapes. According to Purdue University Small Fruit
Specialist Bruce Bordelon, this condition is known to only on the Concord
variety and occurs occasionally, especially in warm years. Uneven ripening
is when some of the berries in the cluster remain sour, hard and green
while others develop the purple color and soften during the ripening
process. The green berries will be full-sized, but will not be sweet.
For some reason, those berries never go through the increase in sugar
and decrease in acids that commonly occurs during fruit ripening. It
is not clearly understood why this phenomenon occurs, but hot weather
is partly responsible.
Once you've made the decision to harvest, you can store the grapes,
possibly up to eight weeks, depending on the cultivar and storage conditions.
Ideally, grapes should be stored at 32F with 85 percent relative humidity.
If you have an abundance of grapes, there are some good alternatives
to eating them fresh. Grapes are excellent for making jellies, jams,
juice and wine.
This information provided on Purdue University Consumer Horticulture
website by Rosie Lerner, Purdue Consumer Horticulture Specialist www.hort.purdue.edu
