Mixed Fruit Set.

After flowering comes fruit set. This is the time to begin evaluating how well the bunches have set in order to estimate yield.

Each individual immature grape has up to four seeds contained within it. Depending on how many of those seeds are pollinated will determine the eventual size of the berry. The more seeds that are pollinated the larger the grape will be.

This is the reason most seedless grapes naturally carry small berries within the bunch and commercial manipulations to increase berry size need to be performed for retail sales.

When the weather is cool and showery, as they have been this year, often grape clusters will set many different berry sizes with the smallest ones never ripening at all. The french call this "millerandage" while in english uneven fruit set is sometimes called "hen and chickens".

Here is a grape cluster showing typical signs of uneven fruit set.

Compared to this one which is much more evenly set. It should produce a decent bunch eventually.

Likewise this Chardonnay bunch looks reasonably well set. Chardonnay naturally grows a large amount of small bunches.