Are you one of those home gardeners that don't know the three stumbling blocks to successfully growing grapes in your backyard? Don't worry, you're not alone.
I have grown grapes successfully under the worst of conditions since 1975 and I can tell you that most of the problems gardeners encounter are because they don't understand the nature of the beast that they are growing. So let's look at the problems that I see when people, like you, have me come and analyze what problems they are having growing the backyard grapevine.
The first problem I see is that gardeners want to grow some grapes but they are unaware of the variety they are growing and its growth habit. This leads to many problems from the get go. Each variety has to be treated as an individual. The most common varieties in local nurseries are either Concord types or the European vinifera grape. It all depends on whether you live East or West of the Rockies. In the East, Concord types are common. In the West, especially along the Pacific Coast, you will find the vinifera varieties. Each distinct type have differing growth habits and this influences what you will have to do to maintain them.
Concord types have a more drooping habit of growth. Vinifera types are more upward in their growth habit. What does this mean? It means that each type has to be trained differently because they grow differently. Because the Concord types droop, they must be trained high and allowed to droop downward during the growing season. The vinifera types must be trained low and allowed to grow upward. This takes advantage of the natural growth habit and maximizes the sunlight into the leaves to get the best ripening conditions and yield of grapes.
Each variety varies in how vigorous the growth is. This trait determines the distance between vines when planted. Low vigor vines must be planted closer while high vigor vines need more space. You don't want high vigor vines planted close as they will run into each other and be hard to maintain over the years. Conversely, low vigor vines planted farther apart will leave gaps of space that will never be filled and you will lose yield because of this.
Gardeners must also be aware of the ripening habits of the variety. Some varieties ripen early and are grown in areas where the growing season is short. Others need much more time to mature. These are late varieties and will need up to 170 days or more to ripen. Then there are those that are in between. You have to select the varieties that are adapted to your growing conditions. Your local nurseryman should be able to help you out there.
One last thing when considering varieties is whether you want to eat them or make wine. Table grapes are to be eaten and wine grapes obviously are to make wine from. The two types are distinct and you can't make wine from most table grapes as they don't get high enough in sugar content and the acids are too low to balance the wine. While wine grapes are small berried and seedy, not suited for eating.
The second big problem I see is that the vines are a tangled mess. Vines need maximum exposure to the sun to be able to ripen the grapes. When they are allowed to grow out of control, the vine leaves begin to shade the vine and this allows for disease and insects to set in (some varieties will need spraying throughout the growing season for disease and insect control), and for less than optimal conditions for ripening the fruit properly. Vines must be pruned properly each year for maximum fruitfulness and health.
Pruning means removing 75-90% of the previous year's growth. This seems drastic but it maintains the health and vigor of the vine. It also means the maximum production of fruit and the best ripening conditions. You can't ignore pruning the vine each spring. It is a must! There are various styles of pruning. These are dependent on the variety and its growth habit. Some varieties are pruned long and some require short "spur" pruning.
Long pruned vines are not fruitful in the bottom, (basal buds). The maximum fruitfulness on these vines comes from the middle buds on the canes from last year's growth. Varieties that bear fruit from the bottom, basal buds are spur pruned. Pruning is an art in itself and comes out of a knowledge of how the vine grows. But if not done, the vine will be shaded, get diseased, and overbear, thus weakening the vine. Not pruning will lead to lowered yields and improper ripening. It can also lead to the death of the vine over time. This is especially true in areas with winters. Pruning will instill more winter hardiness because of healthy growing conditions.
Harvesting too early is the last major problem I see from backyard gardeners. People seem to think that as soon as the grapes begin to color that they are ripe. This can be far from the truth. Coloring, known as verasion, occurs weeks before the grapes are actually ripe. Grapes need to attain a good sugar content and acid balance before they can be harvested. Many people harvest their grapes before they have reached this point and are disappointed in the taste or the wine made from these grapes.
Here again, varieties differ in when they are ripe. It is best to use simple qualitative analysis to determine ripeness. The easiest way is to purchase a refractometer to determine the sugar content of the berries. Table grapes can be harvested between 16 and 18% sugar. Wine grapes usually need a sugar content of around 22-24% sugar or more to be harvested and obtain the right alcohol content of the wine.
Growing grapes in the backyard or garden can be a rewarding experience if done correctly. If grown haphazardly, the vines can become overgrown, tangled messes and never ripen properly. Often leading to death of the vine or disappointment at least. You should read as many reference books on the subject as you can before starting out to plant your backyard vineyard. The more you know about the grapes you are planting the better.
More information on growing grapes (especially under marginal conditions where grapes are not usually found growing), can be found at Jim's website. Just visit: http://www.ristcanyonvineyards.com