Water can also be brought in through osmosis. When the osmotic pressure of the root cells is greater than the soil moisture, moisture then moves into the epidermal cells of the vine roots.
Bleeding is not harmful to the vine and it is a normal process. In fact, it does some good, pushing out air bubbles from the plant's vascular system. The water pressure also stops some wood diseases that could try to enter inside the wounds after pruning.
The Bud Break
As temperatures begin to warm in the spring, stored starch is converted to sugar and sap begins to move in the vine. Buds begin to swell, then burst (break). The newly emerged shoots grow very rapidly, and will continue to do so for several weeks in the absence of stress. Soon cluster inflorescences become visible, usually opposite the third and fourth leaves on a shoot.
I stopped in a vineyard in Saint Helena this morning. In the middle of March, the dormancy period of the vines is over. Depending on the vine variety and vineyard location, bud break can take place over a two month period throughout the Napa Valley.
With such great viticultural diversity, one might think that Napa Valley is quite large. However, our little region is only 30 miles long by five miles wide at its widest point. Only 9% of Napa Valley is planted to grapes and the region has just one-eighth of the vineyard acreage of Bordeaux.
The 2018 vintage has just begun. Vineyard managers need to be very vigilant regarding the dangers of fungi and frost at this time of the year. Over the next couple of months, we will look at the next stage of the grapevine's vegetative cycle – the flowering and fruit set.
