Growing Grapes

Photo
The grape vine on the right is a Flame Seedless variety. It is growing on an east facing wall so it receives full sun in the morning and afternoon shade. A wooden trellis has been attached to the wall to give the grape something to climb.

This grape vine is planted in the grass where it only receives water from the sprinklers. The grass is trimmed up to the base of the grape vine, and care is taken to not ding the base of the vine when mowing the lawn. This vine has never been fertilized and yet grows vigorously.

Flame seedless grapes are ready to be picked in the middle of June and are an excellent variety for the Phoenix Arizona area.

Overview
Grapes grow very well in the lower desert, and are even grown commercially on a small scale. They do best with a fair amount of direct sun and regular water and can take the summer heat and winter cold. European grape varieties with high heat requirements are recommended.

Fruit
The best grape varieties for the Phoenix area are in the European class (Vitis vinifera). Flame seedless grapes and Thompson seedless grapes are both in this class and these plants can be easily found for sale locally. The lower desert summer heat encourages these varieties to produce lots of sugar, creating a wonderfully sweet flavor. Interestingly, the heat also keeps some pigmented grapes from attaining full color, even when they are fully ripe. For example, flame seedless grapes stay green during the hottest months even when they are ready to eat. This requires one to perform taste tests for ripeness before picking them.

For a home gardener, a grape vine can be allowed to sprawl out on a trellis, fence, or wall and over time fruit will be produced. The grape enthusiast will want to maximize yield by pruning the vine. More information on grape vine pruning can be found at the following links. Both Flame Seedless and Thompson Seedless grapes should be cane pruned.

Pruning Grapevines

Grape Training Systems

Heat Tolerance and Sun Exposure
Grape vines need at least a half day of direct sun to grow well and produce. They take the oven like heat of summer afternoons in the Phoenix area very well as long as they have adequate water.

Cold Tolerance
European grapes are hardy down to 5 degrees Fahrenheit so there are no concerns about frost damage in Phoenix Arizona. Grape vines are deciduous, so they will be leafless and dormant during winter.

Watering frequency
Grape vines do well on a grass watering schedule.

Watering method
Basin, flood, or sprinkler irrigation are suitable for grape vines.

Planting
Dig a hole at least twice the size of the rootball. At a minimum, make the hole 2 feet in diameter and 2 feet deep. Back fill the whole with the same native soil that was removed. It also is a good idea to finish with the hole an inch or two recessed so that a watering basin is formed. After planting, spread a thin layer of compost on top of the soil to help conserve moisture and to supply some nutrients. Do not fertilize the newly planted vine until it has been vigorously growing for a couple of months.

Fertilizing and Growth Rate
Regular applications of a balanced fertilizer during the growing season will benefit grape vines. Grape vines do not burn easily from fertilizer so chemical or organic fertilizers are suitable.

Propagation
Grapes are propagated by cuttings and grafting and will not come true from seed.

Pests
Grape Leaf Skeletonizers, a type of catepillar, are a problem in the lower desert. I have just one grape vine so I originally controlled them through manual squishing. I did not find the caterpillars hairs to be a problem, although some people with more sensitive skin can find them irritating. I squish the caterpillar with bare hands using a finger tip rolling motion. I do avoid touching my face and eyes and other more sensitive skin until I have washed off my hands well. I must admit that the adult form of this caterpillar is quite beautiful, being an iridescent blue/purple colored moth.

I originally only had problems with grape leaf skeletonizers in fall months but now they are a problem through all the warm months. In fact, it is getting hard to keep up with them so I have started using a caterpillar killing spray called BT. It is one of the best options for the home garden containing a bacteria named Bacillus Thuringiensis (BT), which sticks to a plants leaves and gives the caterpillars a fatal tummy ache. Brand names for BT include Thuricide and Dipel. They are apparently safe for other creatures in the garden, even other insects, and are not hazardous to people. The only problem with BT is that it is photo degraded, so it does not last very long on the leaves, meaning it needs to be reapplied frequently. I apply it once a week when I see the catepillars and their damage begin, and keep at it until they have disappeared. BT is working very well and is much easier than squishing several hundred of them. To apply, I pour a half of a cap full of the mixture into a one quart spray bottle diluted with water and spray the entire bottle worth on my grape vine. The mixture smells very similar to stagnant pond water.

Another skeletonizer control option is a product called Spinosad, with has the brand names Entrust Naturalyte, and Monterey Garden Insect Spray . It is a chemical produced by soil microbes and is fatal to insects but not harmful to mammals. It also is photodegraded, so will not persist very long. In general, it appears to be slightly more toxic than BT because it persists in water and is more hazardous to other insects.

Carbaryl which has a brand name of Sevin is the harsher chemical alternative for killing grape leaf skeletonizers. It was invented in the 50's and has all of the toxicity one can typically expect of this type of product. Therefore, if used make sure the instructions are carefully followed and precautions are taken. It persists on the plants for quite some time, which means it will not need to be reapplied frequently.

There are evidently fly and wasp parasites of skeletonizers released by commercial growers in California. Also, a virus has been introduced into the skeletonizer population in California which has been generally successful in reducing their numbers. Neither the wasp or the virus control appear to be available to the home gardener here in Arizona.

Birds eating your grapes is another problem. I have tried to cover grape bunches with white paper lunch bags but this seems to interfere with the proper ripening of the fruit and encourages molds. Instead, do what the commercial growers do and cover you entire plant with a bird net. When the grapes are very green, the birds won't bother them but as soon as they start to get soft the fruit will need to be protected.

Links to more grape growing information

Growing Grapes in Arizona      Growing Grapes in Your Home Garden      Growing Grapes in New Mexico