How do you care for Concord grapes?

Grapes are a fun garden fruit for the gardeners in Kentucky. These woody vines need something robust to grow on and suitable growing conditions to produce fruit. They should be grown in at least 8 hours of direct sunlight per day; good air circulation is equally important. Vines adapt to many types of soil, but perform best on a nutrient-rich, well-drained soil.

If you have not had your soil tested, you can contact your cooperative consulting office. The results of the soil tests will show you whether you need to make pH and/or nutrient adjustments specifically for grape cultivation. Grapes prefer a soil range between 5.0 and 6.0. Appropriate growing conditions help prevent potential insect and disease problems. Vitis labrusca 'Concord' is a Native American that thrives in Kentucky. They tend to ripen unevenly, and if picked too early they are not as sweet as others.

The more sun the vine receives, the sweeter the fruit is. Once the grapes have turned dark purple and appear ripe, they can be left on the vine for up to 2 weeks for optimal sweetness. Thinning out the grapes during the first weeks of fruit set also contributes to the sweetness.

As for transplanting, this is best done in late winter or early spring. At this time we are too late in the growing season to transplant the plant without exposing it to the risk of winter injury. Depending on the age of your vine, it may be a job to take out the roots, but to take out as many as possible. Cut the vines back to about one third of their current size. Preparing the new hole before digging the vine helps to avoid transplantation stress. Avoid fertilization in the first year and give plenty of water. Since grapes are produced on the growth of previous years, after pruning and transplanting, fewer grapes are expected in the next season.

Vines require annual pruning and year-round weed control. All plant remains should be removed to prevent wintering of insects and diseases. Always use clean, sharp pruners and if any canes have fallen ill, disinfect them between prunings to prevent the spread of disease. 

from https://www.kentuckyliving.com/home-garden/ask-the-gardener/care-concord-grapes