Grapevines go dormant (go to sleep for the winter) following harvest. The timing of dormancy varies depending on location. Our estate vines here on the winery property and most grapevines in North Central Texas are harvest from late July to mid-September depending on variety. They usually enter dormancy between November 15 and December 15. One knows that dormancy is achieved whenn all of the leaves have fallen from the vines and the shoots are no longer green but brown. Once the leaves have fallen and the shoots are brown, the nutrients and water have migrated down the trunk into the roots beneat the surface of the ground. This offers protection from freezing until spring. Grapevines requires very little maintenance during dormancy, especially nutrient or herbicide and insecticide maintenance. However, there are two very important mainenance activities:
- Pruning. This is critical and in North Central Texas, the timing is very important because pruning too early can stimulate bud break and as stated above, we want to avoid early bud break because of late spring freezes. Once the vines are dormant, we prefer to wait until late February - early March to prune.
- Sufficient water supply. Although grapevines do not need as much water during dormancy, it is possible to have periods of drought. It is important to monitor soil moisture and irrigate if the roots do not have adequate access to soil moisture.
Sometimes in Texas we have warm days in the early spring (late February - early March). When this happens, it is possible to have early bud break and then a freeze in mid to late March that can destroy the primary crop for that year. Some varieties can still have a secondary bug break, but it is usually much less productive than primary bud break (10% to 40% of normal crop load). Normally, early spring freezes do not kill the vines. This, however, is possible if the freeze is severe (temperatures less than 15 degrees F).
Bud break normally takes place here between early to mid-March. There will be small green leaves budding out on pruned spears that begin to develop into shoots. Dormancy is over. These buds will develop into long shoots (3-5 feet or more). These vines then experience bloom in mid to late April. Bloom is when the small clusters shed their flowers and then develop into clusters of small grapes.