Harvesting time is late summer to September and this is best seen through experience and the variety of your plant. It is ready for harvesting when the grapes begin to swell. Then will come a point when they cease to swell and begin to ripen. This is recognized by the transparent appearance of the berry.
After this the quantity of the sugar in the berries will increase quickly in the warm season and the acidity will start to decrease at the same time. The grapes are normally ready for eating before they have enough of sugar to make a good wine, but if it is a wet autumn, watch carefully and pick before the berries start to rot on the plant.
It is usual to permit a little rotting in order to make sure that the berries are as ripe as possible.
Some of the best hybrids and varieties are Schuyler, strawberry grape, Excelsior, Brant, the muscat varieties like Queen, de Saumur, and Hamburgh. You may want to look at local varieties which grow very well in your area.