Grape Vine Canopy Management

You probably will ask yourself what canopy management is and why you must manage the canopy. A simple answer is to expose the vine to as much direct sunlight as possible. You will notice that I hammer on sunlight exposure in almost all my newsletters and in the Complete Grape Growers Guide. This is for a good reason, as exposure to sunlight is one of the most important things, you as a grape grower must keep in mind - ALWAYS!

What is a normal or ideal canopy? A few lateral shoots, shoots with big leaves, moderate internodes and a length of 4-5 feet is characterize an ideal canopy. On a canopy like this, almost all of the leaves and buds and shoots are exposed to direct sunlight. The airflow (ventilation) of the vine is good, which will help the prevention of diseases.

When planning a vineyard, no matter what the size, you need to know how fertile your soil is in order to decide the size of your trellis. A too small trellis with a vigorous growing vine, will compact the vine to much and now airflow or sunlight penetration can take place. On the other hand, a too big trellis on a not so vigorous growing vine, is a waste of money, as building a trellis can be quite expensive. The planting distances, also vary on different soil types, which will have a direct influence on the canopy growth. Planting vigorous growing vines too close to each other or making the rows of the vineyard too narrow will also compact the canopy of the vine.

Another reason all grape growers strive to have a well-balanced canopy, is that it reduces the amount of labor it requires to successfully grow grapes. A too vigorous vine will have many shoots to prune during winter, and could take up twice the time to prune than a grape vine with an ideal canopy. Summer treatments, like suckering, removing of leaves, removing of side shoots and the prevention of diseases is much more difficult when the vine has grown too much.

Normally the reason why a grape vine grows too vigorous, or why the canopy of the vine is too compact is over-fertilization or over-irrigation on fertile soils. The amount of nitrogen a grape vine needs per year, differ from soil to soil, but a rule of thumb is 120kg N per year. Just to give you an example; one vineyard of Sultana on my farm, gets only 55kg N per year, because it grows on deep, very fertile, sand/clay soils.

If your grape vine is under-vigorous, you can try a few things. Don't let these vine bear to many grapes, as it will only prevent the vine from growing as it should. Determine why the vine isn't growing well; look for symptoms of virus infections, see if you have watered the vine enough by digging a hole next to the vine and at the same time have a look at the structure of the soil and how the root system has developed. Sometimes it happens that a clay layer can prevent the roots from spreading into the sub-soil.

If you find, during the growing season, that your grape vine is growing to vigorous and you are the canopy of the vine is getting too compact; there are a few practical things you can do to try to stop the vine before it gets out of hand.

Removing of leaves - this is done by hand and all the leaves close to the cordon or arms of the vine should be removed. Also, remove leaves in the bearing area of the vine (close to clusters). Removing these leaves will ensure better sunlight penetration and airflow. Do not expose clusters to too much direct sunlight, as it will scorch the skin of the grapes, especially if you have a hot climate. Remove leaves after fruit set a then again at varaison (coloring).

Suckering - Remove all water shoots from the cordon or framework of the vine. Under developed and non-bearing shoots can be removed as well, if you find that suckering only water shoots wasn't enough. Keep in mind that you need prune wood the following winter and never leave less than two shoots on a spur. Suckering shout be done before flowering and never during flowering as this will stimulate more growth that can lead to abortion of fruit.

Placing or twining of shoots - The placing or twining of shoots is a well-known manipulation of the grape vine and this should be done when the shoots are about 12 to 16 inches long. Cover the as much as possible wires on the trellis so vine will have maximum exposure to sunlight.

Summer pruning or topping - When your grape vine grows on an arbor or high trellis, and the placing of shoots is difficult, you can summer prune excessive growth by removing the growing point of the vine. Summer prune when the vine has overgrown the trellis, and in this case remove more than just the growing point.