Annual Grapevine Growth Cycle
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Many of us in the Indiana Uplands American Viticulture Area are walking the rows in the vineyards at this time of year with our pruners in hand. How we cut and snip our vines has a direct effect on the quantity and quality of our grapes. With wines containing upwards of 1500 natural chemical compounds, precision in the vineyard is of utmost importance.
Additionally, many of us are preparing our lands to plant new vines. Planting vines normally occurs in the Uplands area from March through May. Basically, the plants need to be planted during their dormancy phase to ensure proper adaptation to their new environment.
At this time of the year, we get many questions about our vineyards and what goes on during this active time of the year. So we thought it might be kind of cool to give you an idea as to what is going on with our vines.
A grape vine growth cycle occurs in 6 distinct stages. Each stage is crucial for the outcome of the grape during harvest and for future grapes on that vine the following season. During each stage, a vineyard manager will monitor and manipulate the vine to affect lifecycle, flavor, and growth capacity of the grapevine.
Stage 1: Weeping
When temperatures begin to rise during early spring, stored starch (stored in the vine during dormancy) converts into sugar, making sap. This sap begin to weave through the vine and “bleeds” out of any pruning wounds it finds. This is the first sign that the vine is ready to start growing.
Stage 2: Bud Break
The stage occurs when buds begin forming on the vine. When temperatures begin to get warmers, the buds swell and then burst. Shoots emerge and grow rapidly at this point. However, the vines are very vulnerable to damaging frosts at this time, and precaution must be taken.
Stage 3: Early Grape Development and Flowering
During early grape development, sugars are not forming but the maximum yield for each vine is set. The flowering stage follows, which can vary greatly in length depending on conditions. Once the flowers abscise, small grapes begin to form.
Stage 4: Fruit Set
This stage signifies the grapes’ maturation process. The grape flesh and skin tannins begin to develop at this time, and a vineyard manager will prune and fruit that is not maturing properly.
Stage 5: Veraison
During this stage, the grapes will begin to change color. While still sour in this stage, the grapes are actively collecting sugar and softening. This stage is extremely critical to the outcome of the grapes during harvest. Vineyards workers must prune the canopy and excess grape clusters to ensure that the grapes will continue to mature at the correct levels for harvest.
Stage 6: Harvest
The vineyard manager will decide when harvest will occur, but it traditionally happens 100 days after flowering. The manager will decide on a harvest date based on the grape variety, sugar, and acidic levels of the grapes. Another factor is how quickly the chemistry changes in the grapes. For instance, Pinot Noir ripens extremely quickly and can fall apart in a blink of an eye whereas chambourcin ripens more slowly so we can be more patient with this grape. Once the harvest is complete, a new life cycle of the vine begins.
Stage 7: Hardening off for Dormancy
The vineyard’s leaves will start turning colors. Some varieties give us some nice red colored leaves, others yellow, and others simply brown. But brown is the color we want to see on the canes – the new wood that started off as green shoots which produced both the fruit for this year’s harvest and the buds for next year’s fruit. A good hardening off cycle means that the vines are fully preparing for winter’s dormancy phase. Once the fall frost arrives, the vines quickly drop any remaining leaves and the vines stay as they are until we’re ready to walk the vineyard again to prune.
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