The Desert Southwest, with its long sunny days and low humidity, is an exceptional place to grow both table and wine grapes. While our climate is generally favorable, success depends on rich, well-drained soil and a consistent seasonal maintenance program to manage the desert’s unique pest and soil challenges.
Soil Preparation & Amendments
Grapes require a rich, loose, and well-drained environment. Desert soils are often alkaline and compacted, making preparation vital to prevent root rot.
- The Mix: Amend your native soil 50/50 with Dr. Q’s Paydirt® or Dr. Q’s Vegetable & Herb Planting Mix to improve organic content and root penetration.
- The Biological Boost: Incorporate Worm Castings (10-20% by volume). This improves the structure of heavy clay and introduces beneficial microbes that help unlock nutrients.
- Drainage: Grapes hate “wet feet.” If you have heavy clay, plant on raised mounds to ensure water moves away from the root crown, preventing rot.
Fertilizing for a Bountiful Harvest
To support vigorous spring growth and heavy fruit production, a consistent feeding schedule is essential.
- The Choice is Yours: We are proud to offer Dr. Q’s® Fruit Tree & Nut Food and Dr. Q’s® Organic Fruit Tree & Nut Food. Both are specifically formulated to provide the micronutrients grapes need in our high-pH soils.
- When to Feed: Apply your first round of fertilizer in early spring as winter pruning concludes and buds just begin to swell. Follow up with a second application in early summer once the fruit has set; providing nutrients when the grapes are the size of a pea ensures the vine has the energy required to produce a heavy, high-sugar harvest.
Pruning and Training Systems
Grapes fruit on wood that grew during the previous season. To ensure a productive harvest, major pruning must take place during the winter dormant season (typically December through January).
- Two primary training techniques
- Rod Renewal (Cane Pruning): Fruiting shoots develop from scratch each year from long canes. Best for Thompson Seedless and Perlette.
- Rod-and-Spur (Spur Pruning): Main stems are permanent; fruiting growth is cut back to short “spurs” with 1-2 buds. Best for Wine Grapes and Red Flame.
- Thinning: For larger table grapes, use scissors to remove 1/4 to 1/3 of the grapes in a bunch. In autumn, remove leaves covering the fruit so sun can reach the bunches to increase sugar levels.
Seasonal Pest & Disease Protection
Proper timing of preventative sprays can save your crop.
1. The Dormant Season (Late Winter)
Before the buds open, apply a Dormant Spray Oil combined with a Copper Fungicide.
- Why: The oil smothers overwintering scale and mite eggs, while the copper prevents Powdery Mildew and Anthracnose spores from activating in the spring.
2. Growing Season Pests
- Spider Mites: Common in dusty desert heat. They cause yellow, stippled leaves.
- Solution: Wash foliage frequently and use Insecticidal Soap.
- Grape Leaf Skeletonizer: These yellow caterpillars feed in rows, leaving only the “skeleton” of the leaf.
- Solution: Treat with Bonide® Captain Jack’s Dead Bug Brew (Spinosad).
- Grape Leafhoppers: Small, wedge-shaped insects that jump when disturbed, causing pale spotting on leaves.
- Solution: Use BioAdvanced® Fruit, Vegetable & Citrus Insect Control or insecticidal soaps.
Essential Problems & Solutions
| Problem | Symptoms & Causes | Solution |
| Powdery Mildew | White, dusty coating on leaves/fruit. | Apply Copper Fungicide in dormancy; improve airflow by thinning leaves. |
| Bird Damage | Birds eating ripening fruit. | Protect with bird netting as soon as fruit begins to change color. |
| Sunburned Fruit | Grapes look shriveled or “cooked.” | Use 50-60% shade cloth during July and August. |
| Skeletonized Leaves | Leaves eaten down to the veins. | Apply Spinosad (Captain Jack’s) at first sign of caterpillars. |
Popular Varieties for Our Climate
In the Desert Southwest, the harvest window is typically early July through late September, though specific dates depend heavily on your elevation and the grape variety. Because of our intense heat, grapes ripen faster here than in cooler coastal regions.
Harvest Timeline by Variety
| Variety | Typical Harvest Window | Characteristics |
| Perlette | Late June – Mid July | The earliest seedless green grape to ripen. |
| Red Flame | July – Early August | Handles heat exceptionally well; harvest once deep red and sweet. |
| Thompson Seedless | Late July – August | Turns from green to a translucent gold when peak sugar is reached. |
| Wine Grapes (Whites) | August | Chardonnay and Sauvignon Blanc are usually picked early to preserve acidity. |
| Wine Grapes (Reds) | Late August – September | Cabernet and Zinfandel need the extra heat to develop bold sugars (Brix). |
| Concord | Late August – September | A late-season favorite; best flavor develops as nights begin to cool. |