Leaf pulling or the removal of leaves is one of the summer manipulations you simply cannot just ignore, if you are serious about growing good quality grapes.
Why leaf pulling? Not only will leaf pulling improve the coverage and penetration of your spray applications, but it will also improve sunlight penetration and airflow into the vine, which on the other hand makes your grape vines less susceptible to diseases. As the UV-rays and air penetrates the vines, it will create less ideal conditions for the inoculation and spread of fungal diseases. Remember for fungus diseases to spread, a hot humid climate is needed. The removal of leaves will allow the vines to dry off much quicker after rain or heavy dew and thus will make the vines less susceptible to the spread of fungus diseases.
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Many grape growers ask me why their vines dont have any grapes and the first question I ask them is how they do summer manipulations. In 90% of the cases, they don't do leaf pulling. I will almost go as far as to say that, leaf pulling is just as important as proper pruning techniques! I know, this is a bold statement, but without proper sunlight penetration, the chances are good that your vines will only have shoots and leaves and no grapes!
Leaf pulling is done just after flowering, when fruit set is complete so you won't disturb the pollination process. In the southern hemisphere, it is round about middle to end November and in the northern hemisphere in May (off course this may vary from climate to climate). If you grow table grapes or dessert grapes, then leaf pulling will improve the overall cosmetic quality of the grapes, as it will minimize the bruising of the grape skins from leaves scratching it's surface. For wine and table grapes, it will improve the overall grape and wine quality, as the vines are using the nutrients available more efficiently.
Tests done with a light sensitivity meter shows that the first layer of leaves on the grape vine canopy, get the most sunlight and will use the sunlight to produce more than 90% of the carbohydrates inside a vine. They are the most efficient leaves on the canopy, which is obvious as it gets the most exposure.
The second layer of leaves inside the canopy, only gets about 7 - 10 % of the sunlight and will contribute only that percentage to overall carbohydrates.
The third layer only receive about 3% of the sunlight. Now, the following is important; your grape vine needs leaves to produce carbohydrates, but on the other hand use up nutrients for normal assimilation processes. Therefore, some leaves are using energy they produce to create more energy but some are only using energy and do not produce enough energy themselves. These are the leaves that will make less energy available for grape development and they need to be minimized at all cost. The leaves at the base of each shoot (leaves 1 to 3, counting from the spur or cane) are the ones that are not contributing to improve grape quality.
By only removing those leaves, you will improve the sunlight penetration into the base of the canopy and will also improve the airflow by up to 40%! Leaves touching the structure or cordon of the vine and those touching grapes clusters needs be removed. Don't forget leave pulling, I know it's a time consuming job, but you will reap the rewards in the end.
Leaf Pulling Grape Vines
Danie has been growing grapes commercially for more than a decade and owns an export table grape farm. For more grape growing tips like this one, please visit My Grape Vine
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