Why Are Our Grapevines Not Producing Fruit?
Grapevines can fruit for years if they are handled properly. The current year's grapes grow on the current year's shoots. But those shoots come from last year's buds. Protecting the buds throughout the winter and pruning the perennial parts of the vine correctly are essential practices. The perennial parts are the roots, stem and cordon, the horizontal extension of the main stem. Wild grapes have both male and female genders. But most planted grapes have both male and female flowers and they self pollinate, so this is rarely the reason for a lack of fruit.
Cold and Frost
There are a few reasons grapevines don't fruit. Winter damage from cold, untimely frosts, the age of the vine and pruning too little or incorrectly are the main culprits. Most grapes that can thrive in North America have a cold hardiness of down to zero degrees, but not much lower. Damage is done when cold snaps hold on for days. Another problem is when a hard freeze follows a warm period in winter. Frost hitting after the vines have budded is another problem. Vines will bud twice, but if both sets of buds freeze there will be no grapes.
If your grapes have been planted within the last three to four years they may not yet be capable of fruiting. It takes them a few seasons to develop mature wood and build up sufficient nutrients in the plant to produce fruit. Vines that are very old may need food or more vigorous pruning to keep them fruit bearing.
Grapes must be pruned a lot and pruned correctly. If pruning has not been done correctly at any time, you might not see grapes until the problem is corrected. Most grapes that can thrive in North America should be pruned to leave five nodes per cane. Spur pruning is used on European grapes. It means pruning them to less than three buds. If you are pruning with this method, stop and let them grow more than three buds before pruning again.
Phenoxy herbicides can retard fruit production on grapevines especially if the exposure occurs early in the season. The spray from such herbicides can carry quite far, up to two miles. Even if you are not using them on your vines, they can be exposed if you are using them on other plants or if your neighbors are.