In south central Michigan the growing season is 150 to 160 days long. This is barely enough time to grow a standard variety like Concord that needs 160 to 165 days. Varieties listed in the variety section are early to midseason varieties. The vines are healthier if good weather occurs after the crop is produced so the vines recover from producing the crop and have time to get ready for winter.
The soil should be well drained, 30 inches deep and with a pH of from 5 to 8. An excessively rich soil, high in organic matter, produces heavy, late maturing crops with a low sugar content. Light soils produce light yields of early maturing fruit with high sugar contents but vine growth is weak.
There should be a minimum of cold-warm-cold cycles during the winter. Exposure to alternating cold and warm temperatures causes much winter injury. The site should allow for good air drainage to reduce the amount of frost injury.
When selecting varieties consider the number of days required to mature the crop and the cold temperature hardiness. Varieties listed below mature fairly early and are hardy. Other varieties should be considered only if they mature in a reasonable time and are listed as hardy. Other characteristics would be the type and uses of the fruit.
Concord--160 to 165 days, a blue variety, hardy, fruit good for juice, jelly, jam, wine Niagra--150 to 155 days, a white grape, somewhat less hardy than Concord Delaware--150 to 155 days, a pink-red grape, somewhat less hardy than Concord, low vigor Fredonia--146 to 151 days, a blue variety, less productive than Concord Golden Muscat--a white variety, vigorous, productive Moore Early--146 to 151 days, a blue variety, fruit quality not as good as Concord, the fruit sometimes cracks badly Beta--very early, very hardy, productive, a blue grape, berries with high sugar and acid Seyval (Seyve-Villard 5-276)--Early midseason, a white grape, moderately vigorous, productive
Plant grape vines in the spring. Nurseries offer either 1 year or 2 year old plants. The 2 year old plants cost more than 1 year old plants. The cheaper one year old plants give as good a result as the more expensive 2 year old plants.
At planting time cut off dead or broken roots and prune back the tops to 2 or 3 buds. Set vines at 8 foot spacings in rows 8 to 9 feet apart. Plant the vines 2 inches deeper than they were growing in the nursery. Do not set vines close to trellis posts. The posts may have been treated with a preservative that may injure the vine. Set the vines directly under the trellis. After planting give each vine 1/2 cup of 5-10-10 or similar analysis fertilizer. Apply the fertilizer in a 3 foot circle around each vine.
Only one type of trellis and training method will be discussed. The trellis is the two wire trellis. Use durable posts about 3 inches in diameter. About 2 1/2 feet of the 8 foot long post should be buried in the ground. Set posts at 16 foot intervals along the row. End posts may need to be longer to give good support and strength. If the end posts are weak or poorly braced the trellis will be weak and sag.
Fasten wires to the post so they slide through the fastening device. This allows the tension on the wires to be increased to keep them taut. The bottom wire should be 3 feet from the ground, the top wire about 5 feet. Number 10 galvanized wire is suitable for use on grape trellises.
The training system described is called the 4 Arm Kniffin. Plants trained to the 4 Arm Kniffin system will consist of a vertical stem which reaches to the top wire plus an upper and lower branch on each side of the trunk. These branches are tied to the wires.
During the first year the strongest shoot is trained to grow upward and is fastened to the first wire. During the second growing season it reaches and is tied to the top wire. During the winter, cut off the portion of the trunk that extends above the wire. During the second growing season, the vine will have sent out side branches near the bottom wire. One branch on each side of the trunk should be trained to grow on the bottom wire. During the second winter these side branches should be pruned back to 5 buds each at the time the excess trunk is cut off. During the 3rd growing season the upper branches form. During the 3rd winter prune as described in the pruning section.
Fruit is only produced on the previous year's wood. Vines allowed to grow for many years without pruning accumulate much old, unproductive wood. The object of pruning is to remove all the old wood and leave 4 canes that will produce next year's crop. The 4 canes are the 4 arms or branches described in the training section. In addition, 2 to 4 other canes, called renewal spurs, are left to produce the fruiting canes for the following year. Renewal spurs only have 2 to 3 buds and like the 4 fruiting canes originate from the trunk.
Grape pruning regulates the health and vigor of the vines. This is done by pruning the vines so the fruit load is about what the vines are able to mature. This is done through a system called balanced pruning. The system is based on the vigor of the vines in the previous growing season.
Grapes are pruned during the dormant season in late winter or early spring. Buds that have begun to swell are easily knocked off during the pruning operation. First, select the 4 canes that will be the fruiting wood for the coming growing season. Also select the canes to serve as the renewal spurs. The renewal spurs should originate on the trunk near the point where a wire crosses. This positions canes properly. Once the renewal spurs and fruiting wood have been selected, all other growth is removed. The wood left should be dark brown and slightly larger than a pencil. The pruned off wood is bundled together and weighed. The total number of buds left on the 4 fruiting canes is determined by the weight of the prunings. The chart below gives the weights and bud numbers.
Weight of Prunings In Pounds Buds to Leave
less than 1 less than 30 1 30 2 40 3 50 4 60 5 70 6 80 above 6 above 80
For example, if the prunings weighed 2 pounds, the fruiting wood should have a total of 40 buds. Each of the fruiting canes would be cut back to 10 buds.
Here is a less complicated method. Select fruiting canes and renewal spurs as just described and take off all other wood. Then, instead of weighing the prunings, just cut back each of the fruiting canes to 12 buds. The renewal canes would still be cut back to 2 to 3 buds.
The vertical shoot that forms the trunk is allowed to grow to the top of the arbor. The laterals are allowed to grow off the trunk at 2 foot intervals and are trained across the arbor. For fruit production, cut the laterals back to 12 buds each winter.
Tying Canes to the Trellis or Arbor
Grape buds are easily knocked off, so early tying minimizes bud damage. The material used should be strong enough to last several months but not be so long lasting it girdles the vine. Tie canes just behind the last bud. This tie may be fairly tight but other ties should be loose enough to allow the cane to increase in diameter.
Frost Injured Vines
If the new growth is frosted it should be removed. Take off both the injured and uninjured portions of the injured shoots. If growth is removed it must be all or none. Partial removal will be ineffective. If the plant has produced considerable growth that is only mildly injured, it is safer not to remove the growth. Underestimating the amount of injury may result in the flowers falling off.
Weed Control and Fertilizing
Control weeds by cultivating no deeper than 3 to 4 inches.
The amount of fertilizer needed varies with the soil. Soil testing and foliar analysis will help monitor plant needs. Avoid giving too much nitrogen.
Grapes should be left on the vine until fully ripe because ripening stops once the grapes are harvested. Color is not a good indicator of ripeness as it changes 2 to 3 weeks before the grapes are ripe. The stem of ripe grape clusters will be brownish and wrinkled. Ripe berries are easily pulled from the cluster.