The Grapevine Vegetative Cycle Part II
The cool days and mornings are pretty much behind us. The spring frost has packed up and left. Weather patterns have become increasingly harder to predict. For example, four weeks ago, a weather event with cold temperatures and hail decimated northern Bordeaux vineyards. In California however, the vines are now just about to flower and start to show a lot of growth.
A Recap of the Vegetative Cycle:
• Bleeding of the vines between February and March
• Bud break in April, dependent upon temperature
• Flowering starts in May, 40-80 days after bud break
• Fruit set almost immediately follows
• Veraison (the onset of ripening) takes place around 40–50 days after fruit set
• Maturation and harvest
After a month or so of vegetative growth, a vine will develop tight bunches of tiny flowers. Each flower has the potential to form a single grape berry. Frost and wind are concerns at this stage of development. When there is a danger of frost, vintners and growers take steps to protect the tender young shoots, including the use of large fans to circulate the cold air, sprinkling the vines with water to form a protective coating of ice (which keeps the temperature constant) or the use of heaters to warm the air temperature in the vineyard. Elevations ranging from sea level to 2,600 feet and variance in temperature from the cooler coastal areas to the center of California both influence the flowering. As a result, this period can stretch over two months, depending upon the microclimate of the vineyard location.
Fun fact: Most cultivated Vitis vinifera grapevines are hermaphroditic, with both male stamens and female ovaries, while many wild grapes are usually male, producing pollen but no fruit.
The now-pollinated flowers drop their petals and a tiny green sphere begins to emerge at the end of the stem. As these grapes grow, bunches begin to take their familiar shape. Frost is still a concern, but once set, the fruit will begin to ripen under the influence of Mother Nature, and of course a bright, shiny sun. The climate of Napa Valley is truly unique, found on only 2% of the earth’s surface. This contributes to the consistent quality found in Napa Valley wines.
At a certain point, the vigorous shoot growth that has occurred during the spring must be managed to ensure optimal grape production and ripening. A complex process, canopy management refers to a variety of decisions and actions related to leaf removal, vigor management, shoot thinning and shoot positioning. The goal is to achieve the perfect balance of shade, sunlight and air circulation around each grape bunch, which will promote optimal ripening. High-end vineyard workers often make more than 20 passes through a single row of vines each year.
In a few weeks, we will be getting closer and closer to a new harvest after veraison and maturation of the grapes. Stay tuned for Part III of the Grapevine Vegetative Cycle, coming soon!