Grapes for Home Gardeners

By Charles Davis, UC Master Gardener 

Photo credit:  cekern.ucanr.edu

Grapes can be grown successfully in the backyard with thoughtful planning and care. Choose a grape variety based on your climate, desired use and support structure.  If the grapes are trained correctly and pruned regularly, you will be rewarded with abundant crops. Patience is required as a healthy well-trained vine will not produce a full crop for 4-5 years.

Choosing the Grape Variety

• Important considerations in choosing a grape variety: Use (fresh eating vs wine), climate and support structure (arbor vs trellis).
• In general, wine grapes have smaller grapes with high sugar. Table grapes have larger berries with lower sugar content. Many table grapes can be used for wine and vice versa.
• 3 types of grapes:
  • European grapes (Vitis vinifera), most commonly grown wine and table grapes in CA. High heat tolerance, cold tolerance to 5 degrees F. with thin tight skins. Table grape - Thompson Seedless, Flame, Perlette, Delight; Wine grapes - Cabernet and Chardonnay; Susceptible to pests and disease.
  • American Grapes (Vitis labrusca), table grapes with moderate summer heat requirements and cold tolerance down to -20 F. Primarily table grapes with slip skins; vigorous and resistant to pests and disease. Concord and Niagara, Price, Vanessa
  • American-European Hybrid Grapes, mostly table grapes. Disease resistance of American with European flavor. Himrod

• Grapes vines will not grow when temperatures are less than 50 degrees F. Winkler scale is based on Growing Degree Days (GDD). One degree-day for every degree over 50 degrees between April 1 and October 31^st. This scale helps guide choices based on climate.
• For the mild summer climate of SLO and coastal regions, early ripening varieties produce best. Good choices for SLO, coastal and South County based on climate include Price, Vanessa, Himrod, Flame, Delight. High summer heat requiring varieties suitable for North County include Thompson Seedless, Black Monukka, Muscat of Alexandria and Ribier.
• Grapes are self-fruitful so no need for multiple varieties or more than one plant.
• Table grapes produce 15-30 lbs. per vine and wine grapes 8-12 lbs. per vine.

Site Selection and Planting

• Grapes will tolerate a wide range of soil types but do require a well-draining soil. Amend with compost to improve drainage if needed. Vines do best with pH below 8.
• Choose a site with full sun, 7-8 hours. North-south orientation of vine provides best sun exposure.
• Consider microclimate of yard. Avoid areas with low settling frosts or wind. South or southwest facing slopes are optimal. Vines stressed by frost or shade are more susceptible to disease.
• Provide a support structure as vines are heavy and vigorous. Support system needs to be consistent with training method and installed at planting.
  • Trellis - Posts with 2 to 4 strong horizontal wires of 12-14-gauge wire. Advantages include easy access to vines with no ladder.
  • Arbor - Good for both fruit and shade; nice landscape accent.
  • Fence - Convenient but expect harvesting and pruning challenges as vine entangles in fence and may cause damage.

Pruning

• In February, plant bare root plants as soon as they arrive. Trim off any broken or excessively long roots. If the roots appear dry, soak roots in water for an hour before planting. Dig hole wide enough to spread roots. Potted 1-year old plants can also be planted.  Plant no deeper than grown in nursery.
• After planting, remove all but the most vigorous cane and prune it back to 2 buds. Space plants 8 feet apart.

Care

• Irrigation depends on climate and soil type but grapes are low water plants. Use drip irrigation for vines; separate from landscape plants. Water deeply, regularly, but infrequently. Soil should be moist but not continually wet. Water needs decrease as fruit sets so water less even during heat of summer.
• Too much water or fertilizer can cause exuberant leaf and cane growth, decreased fruit production and increased disease susceptibility.
• Use 2-4 inches of mulch to conserve moisture. Do not let bark touch trunk of vine.

Training

• Train young vines to establish a single strong trunk and develop a strong vine structure on the support system.
• Methods of training:
  • Head trained method- vine grows as a single leader and is staked, resembling a small tree. It is a good method for cane pruned grape varieties on an arbor but can also be used on post and wire trellis.
  • Bilateral cordon method – vine trained into 2 or 4 arms (cordons). This method is good for spur trained vines on post supported wires or a fence.

First year - let vine grow unchecked during first growing season. In winter, choose the strongest thickest shoot and prune down to 4 lowest buds, then prune off all other shoots.

• For post and wire trellis:
  • Second spring - let buds grow 6-8 inches then choose strongest one, tie to support post, remove all other shoots. If using 2 wire trellis, also choose 2 shoots to tie to the lower wire.
  • Second summer -prune back the lead shoot as it reaches the top wire and once shoots appear pick the two best to train as the arms on the top horizontal wire (for spur pruned varieties) or choose 2-4 shoots (for cane pruned varieties).
  • Second winter - cut all growth except trunk and arms, or chosen canes.
  • Third summer - let grow but remove any additional shoots from the trunk. In the third winter, begin either cane or spur pruning.

• For arbor:
  • Second summer - when vine has reached top of arbor, bend it over and tie to arbor roof. Cut off all side shoots, this will encourage vine to grow.
  • Second winter - cut end of vine where you want last side shoots to grow and remove side shoots.
  • Third spring - prune shoots to one foot apart. From third winter on, spur or cane prune.

Pruning

• Pruning is necessary to optimize bud formation, control over cropping and to improve aeration and sun exposure. The pruning method will correspond with the training method and support structure used.
• There are two dormant pruning methods which begin the third winter: spur pruning (most common) and cane pruning. The type of pruning depends on the variety of grape and choice of support structure. Some varieties are only cane or spur pruned, others can be pruned by either method.
• Summer pruning involves thinning out shoots and leaves for aeration and sun exposure which is important for disease management and ripening of fruit.

Harvest

Pick grapes, one cluster at a time, in the morning when cool. To judge ripeness, taste is simplest method; taste grapes from bottom of cluster as they are last to ripen. Other clues include stem changing from green to brown, darkening seeds or mature grape color. Determine the sugar, acid and pH levels of wine grapes for best harvest date. Grapes do not ripen off the vine.

Pests and Disease

• Powdery mildew - a very common fungal disease of leaves and fruit occurs when temperatures are 70 to 85 degrees F. Initial yellow spots on leaves become fuzzy with a white powdery coating. Prevention is key: do not over water or overfertilize, prune grapes to allow good air circulation and light penetration, choose grape varieties resistant to disease. Shade encourages this disease. Sulfur is used for prevention only.
• Spraying vines with water (not during heat of day) may prevent spread of powdery mildew. This technique is also useful in knocking off ants and aphids while reducing dust which is favored environment of spider mites.

References

Pests in Gardens and Landscapes- Grapes.  UC IPM. http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/grapes.html

Pests in Gardens and Landscapes: Grapes. UC IPM. Managing Pests in Gardens: Fruit: Grapes—UC IPM

Grape: Year-Round IPM Program for Wine and Raisin Grapes. UC IPM. Grape: Year-Round IPM Program for Wine and Raisin Grapes—UC IPM

Growing Grapes (Table, Wine, Raisins) in Your Backyard. The California Garden Web. UC ANR. Growing Grapes (table, wine, raisins) in Your Backyard - The California Garden Web

Ingles, Chuck. “Guidelines for The Home Vineyard.”  Environmental Horticulture Notes. EHN 97. UC ANR. 163138.pdf