Italia, a seeded table grape that can be used for wine as well |
When plants have fewer “children” to nourish, each child as the potential for becoming bigger, healthier and stronger. Thinning a tree or vine to remove fruit is a form of pruning. Fruit is removed when they are very young so that the remaining fruit has enough time to get larger. The earlier you get it done while the berries are small, the greater the amount of food that will be transferred to the remaining berries.
Grapes are thinned in two ways; small bunches are removed and the remaining bunches are “pruned” so that the berries that remain get larger. This is how to do it for table grapes.
After the grapes of flower you will see the development of very tiny grapes at each of the flowers. Space the bunches of grapes so that they are about 12 inches apart along the vine. Look for bunches that are smaller or have not filled out well. Prune these inferior bunches from the vine with a pruning shears and compost them. Cut them off so that you do not leave any stub behind.
Secondly, look at the remaining bunches of grapes. These bunches grow in a triangular shape with a lot more berries at the top of the triangle, closest to the vine, and fewer of them at the bottom of the triangle near the point. Divide the triangle along its length into three equal segments.
Remove the bottom segment, or about one third of the bunch, by cutting with a pruning shears or pinching with your thumbnail.
Yes it’s painful… To you…Not to them. There. You have reduced the size of this family so that the vine can provide more food and make the remaining berries larger.
Improving Size and Quality of Seedless Grapes
http://www.aces.nmsu.edu/pubs/_h/H311.pdf – to the best of my knowledge this was never updated as promised so this is the most recent. Darned useful.