Wintertime in the Vineyard
Several times during the holidays I was asked about what goes on in the vineyard during wintertime. After the fruit harvest, the vines slow down their growth and begin to prepare themselves for fall and winter. Winter is basically a quiet time for the vineyard manager and vineyard workers, however there are several tasks that require attention while the vines essentially go dormant for a period.
Do grapevines get replanted each year? The answer to this oft asked question is NO. Typical grapevines can live and be productive for 20+ years. There are vines in certain wine regions of the world are still producing grapes after 100+ years. Since the Texas wine industry is relatively young, some of the older vines in the state are only 35-40 years old. Grapevines are perennial plants that go through an annual cycle: budding, flowering & fruit set in the spring; leaf & stem growth while developing fruit in the summer; ripening fruit for harvest and continuing photosynthesis until leaves drop in the fall; and dormancy during the winter. The winter dormancy period is addressed below.
Grapevines go dormant after the leaves drop in late fall. The goal before those leaves die and drop is to keep the vine and its leaves healthy so that photosynthesis can build a sufficient carbohydrate reserve in the vine to support budding, flowering and fruit set next spring. These stored carbohydrates “jump-start” the vine until new leaves fully develop and begin photosynthesis for a new growth cycle. Keeping vines properly watered is also important during the winter. If not enough rain falls, periodic irrigation can help the vine to prepare for the new growth cycle in the spring. So, if vines are overly stressed or unhealthy in the fall and drop their leaves too early, there will likely be problems in the spring.
After the leaves drop, a good practice is to clean the vineyard floor. Leaves carrying fungal spores from the current season can be a source of early fungal disease pressure next spring. So, clearing dead leaves is a good practice. The vine’s woody stems become dry and hard as moisture and nutrient flow through the vine comes to a standstill. This helps to keep the exposed portion of the vine from experiencing damage as moisture in the stems may freeze in cold weather. This process is sometimes called “weathering off.”
Other tasks often required during the winter months include evaluation and addition of nutrients to the soil, weed control and trellis management. Vines may need a dose of nitrogen from either fertilizer or mulch, and mineral nutrients, like iron, which can be added in a chelated or soluble form that the plant roots can assimilate during the winter for a healthier spring and summer. Removing weeds, turning them under or treating weedy areas with herbicides can help reduce problems when the vines awaken next spring. With the vine dormant, and with no leaves to be damaged, winter is a good time for this task. And, with no leaves, it is much easier to see where adjustments and tightening in the vineyard trellis system may be needed. Posts can lean and wires can loosen over a full growing season.
A particularly important task occurs at the end of the dormancy period (typically late January through early March), and that is preparation for pruning. Almost all of the vine stems that grew last season, those that produced leaves and held fruit clusters, need to be removed from the vine before it buds out in the spring. New leaves and fruit develop on new-growth stems, so the old ones need to be removed. Cordon pruning is one method used in which the horizontal fruiting arm of the vine is kept, and the vertical stems from last season are removed down to a few inches, leaving 2-4 buds that will develop into new vertical stems in the spring. Cane pruning is another method used in which the fruit-bearing cordon from last season is removed, and a stem or cane based at the top of the vine trunk is bent over to become the new horizontal fruit-bearing cordon for the new season. Some vineyard managers practice pre-pruning, a first pass through to trim the stems extending from the cordon back to about 12-15 inches. In a second pass, later, these stems will be trimmed down to a few inches in final pruning. Others just do the full pruning effort in one pass rather than two.
As you drive around vineyard areas, particularly here in Texas, take notice of the vines and whether they have yet to be pruned, have been pre-pruned or fully pruned. And think about those hard working folks that have tended the vineyards during the wintertime so that new growth will develop in the spring, and a new crop of grapes will be available from which to make wine next summer and fall.