Annual Growth Cycle of the Grapevine
Flowering and Fruit Set
As the new primary shoot develops, flower clusters form opposite a leaf (See Figure 1.2). Where a flower cluster does not develop, a tendril may grow opposite the leaf. A fruitful shoot usually produces one to three flower clusters (inflorescences) depending on the variety and growing conditions of the previous season under which the dormant bud (that produced the primary shoot) developed. Many grape species, including most varieties of Vitis vinifera, form only two flower clusters per shoot. French- American hybrids as a group tend to flower prolifically with four or more clusters per shoot. Location of these clusters on the shoot also is specific.
Millerandage
Millerandage (pronounced mil-ROHN-dahdzh) or “shot” berries on the other hand is a poor fertilization, giving small grapes, without seeds, though which still have the capability to mature and ripen (See Figure 1.4). These exist on the same bunch as successfully set berries. Millerandage is sometimes referred to as “hens and chickens,” where hen berries (the bigger ones) are the result of normal fruit set. Hen berries contain seeds.
Coulure
Coulure (pronounced coo-LYUR), French for “shatter,” occurs during flowering in the spring, wind and rain as well as chemical deficiencies can keep grapevine flowers from being properly fertilized, causing these flowers to drop off the cluster (See Figure 1.5). Since each flower is responsible for a grape, the cluster of grapes that eventually forms is loose and missing grapes. If the improperly fertilized flower stays attached, it produces a puny, seedless grape called a “shot” grape.
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