Nature’s Alarm Clock and the Life Cycle of a Grapevine©


The weather has become so screwy it’s a wonder that migrating birds know when it’s time to come and go or when perennial plants and hibernating animals sense naptime is over. In vineyards, climate change has the potential to disturb the signals that tell dormant vines to get up and going. Changing periods of daylight alert many  plants, like grapevines, that are sensitive to the relative amount of day and night as seasons pass from one state to another. The amount of daylight during a 24-hour period also is important. Variations in air temperature and the angle of the sun also play vital roles. As warm air increases, plant hormones and cells in the tips of a plant’s root triggers the plants to send out new growth. In the case of grapevines, the appearance of buds tells watchful winemakers and vineyard managers the cycle of growth and renewal is beginning. Bud break is the first joyful sign the vines are alive.

John Williams, owner-winemaker at Frog’s Leap Winery in Napa Valley, notes that timing is crucial for grapevines. He says, “ If a grapevine gets up too early in spring, it’s very existence is in peril from crippling frosts lying in wait for its tender young buds. On the other hand, if it decides to sleep in, it may find itself at a competitive disadvantage from adjacent vines eager to grab space in the sunlight. Waking up is one of the most critical decisions the vine will make all year.”

During the long dormant season that precedes new growth, a lot of activity takes place in the vineyard. Vineyard workers are out in the field with pruning shears, tying the vines to supports for stability. Pruning vines sets the stage for the season’s growth, guiding the vine to grow in optimum directions to capture sunlight and moisture.

After a few weeks of vegetative growth, vines develop bunches of small flowers. Each flower will develop into a grape berry. This is a crucial time since frost can damage the potential development of grapes. The pollinated flowers drop their petals and form into tiny green bulbs. As plants develop during the growing season leaf production vies with grape development. Vineyard workers make many passes through the vineyard managing leaf removal and imperfect bunches to assure a proper balance between shade, sunlight, and air circulation around the remaining bunches. All grapes, whether ultimately red or white, hide their true nature and stay green until the middle of summer. The development of pigment on the skins takes place slowly in a process called veraison. Then the grapes continue to ripen until it’s time for harvest, or crush.


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