Increase Grape Berry Size by Thinning Fruit Early

Q. When do you harvest green grapes and how do you increase their individual size?

'Italia' seeded grape ready for harvest in North Las Vegas.

A. Increasing the size of the berries (individual fruit) is a two-step process starting when the berries are very small. The correct time to begin this operation in our climate could begin as early as the end of March or the first part of April. At this time the berries have already begun to increase their size. The correct time to begin is when the berries are about the size of a young, early pea.

Remove small clusters of grape berries when this size

            First, leave only the large bunches and remove any small bunches. You want the average distance between bunches of about eight or 12 inches depending on how much was set. You want the remaining bunches to be big and long.

Remove the bottom 1/3 of the grape cluster by pinching.

            After removing the smaller bunches and getting the correct average distance apart, next reduce the size of each bunch by one third. Pinch the bottom one third of each bunch of grapes and remove it. It will decompose on the soil or mulch surface. The result is a fewer berries and fewer bunches. This results in larger fruit.

1. Keep an eye on your grapes in mid Spring.

2. When grape "berries" are young and pea-sized thin out the clusters.

3. Next pinch each remaining cluster so it is reduced by 1/3.

            This is the “organic” method. There is an “inorganic” method involving spraying the bunches with hormonal sprays when they are increasing in size but the “organic” method should be adequate for most homeowners.

            When to harvest is more difficult with green grapes than red grapes. Green grapes have a slight color change when they are ready to harvest. This change in color of the berries is from green to yellowish green or “bronzy” in color.

To determine the harvesting date, taste a few of the berries. If the berries are to your liking, then harvest them. Birds begin their damage (pecking or stealing berries) when the sugar content rises in fruit. Seldom do they damage fruit when the sugar content is low unless they are a stupid or young and inexperienced. Whenever you start to see significant bird damage, begin harvesting ripe fruit. After the grapes are harvested there is little to no change in “sweetness”.