To achieve the optimal size, sweetness, and raisin yield each year, a method of trimming and handling is done to the vine at each stage of the growing process. This method is crucial to the quality of the raisins, and includes techniques such as, pruning, dropping bunches, thinning, girdling, and leafing.
During the winter the plant lies dormant waiting for spring. As the warmth of the early desert spring takes effect, buds will form at each node. After three or four leaves have developed from each bud, flowers will start to appear. At this stage, the flowers will have feathery tips. These are the parts of the flower that need to be polynated to produce fruit. Pollination occurs by wind, so it’s important for the wind to ripple between the flowers. Plucking off all leaves along each cane below the flowers is what is called “leafing”. This also allows for the plant’s energy to go into filling out the grapes rather than into making new leaves. Vines can overproduce, which results in degradation of quality. To correct this, the process of “thinning” is done to misshapen and excess clusters.