Following the flowering of the Maltese vines reported a few weeks ago, the next stage of ‘fruit set’ is now well under way for certain varieties of Moscato Bianco and Chardonnay grapes growing in two separate Żebbuġ vineyards for Delicata.

Fruit set is when the fertilised flower begins to develop a seed and a grape berry forms to protect it. Climate and the health of the vine play an important role with low humidity, high temperatures and water stress having the potential of severely reducing the amount of flowers that end up getting fertilised.

Two concerns that can cause abnormal fruit set for growers are coulure and millerandage.

Coulure can occur when there is an imbalance of carbohydrate levels in the vine tissues and some berries fail to set or simply fall off the bunch. But this is more prevalent in cooler climate winemaking regions as periods of cloudy, cold and wet weather during the flowering can have a devastating effect on yields for some grape varieties.

Millerandage can occur when some fertilised flowers do not form seeds but only small berry clusters and on the vine one ends up with mixed berry sizes of both large and small berries, often referred to as ‘pumpkins and peas’.

The cause of millerandage is the poor fertilisation of the ovary by pollen, usually due to inclement weather at flowering.

Following fruit set, the bunches will go through the process of veraison in about a month’s time (for certain varieties). Veraison is an intermediate stage of grape berry development which marks the beginning of ripening, where the grapes will change from their hard green state to their softened and coloured form.