Agriculture Reference
In-Depth Information
→ Choose varieties that can ripen with a shorter growing season, such as
Gewürztraminer, Madeleine Sylvaner, New York Muscat, Pinot Blanc, and Pinot
Noir.
→ Spread black mulching material or rocks under the vines to absorb heat.
→ Pull leaves to expose as much of the canopy to sunlight as possible.
→ Develop a good program of control for fungal diseases, which are often worse in
cool, damp climates.
TEMPERATURE AND VINE GROWTH
Grapevines are deciduous, woody plants. This means that they develop a hard, woody
permanent framework that puts out new growth during the warmer months and then enters
a period of dormancy during the winter months. It helps to know the stages of growth be-
cause timing of various tasks is extremely important when maintaining your vineyard.
Dormancy is the period when your vines are growing very little or not at all. Depend-
ing on the soil temperature, the vine may still have some root growth, but where the soil
is frozen, there is likely to be very little activity even in the root zone. Grapevines need
this period of cold, which is why they do not grow in tropical climates where there is no
winter freeze. Some grapevines are able to withstand winter temperatures as low as -45°F
(-42°C). The degree of cold-hardiness depends on the variety and the rootstock.
In spring, rising temperatures stimulate the vine to start converting the starch it has
stored in its woody tissue to sugar. Sugary sap moves through the vine, and growth of the
green tissues starts.
Bud break or bud burst occurs when the average daily temperature is 50°F (10°C).
Shoot development begins right after bud break (the leaves and fruit are produced from
these shoots). Once leaves grow to about half their final size and lose their initial bright
green color, they begin to manufacture new sugar by photosynthesis.
Flowering occurs 30 to 80 days after bud break at 61°F to 68°F (16°C to 20°C). The
inflorescences begin to swell, then open to reveal the small flowers. Most grapevines are
self-fertile, which means they do not need to have male and female plants in order to pol-
linate. Wind and insects do assist with pollination, however.
Berry development begins with berry set or fruit set, which comes 7 to 10 days after
flowering and ends with harvest. In hot climates, the total period from bud burst to harvest
is shorter (110 to 140 days); in cooler climates, it is much longer (190 to 220 days).
Veraison is the mid-stage of berry development when the berry softens and changes
from green to its final color (amber, black, blue, golden, pink, red, or yellow).
