Growing Grapes

Ever wonder why the same grape can produce different flavors in different areas? The site's geography, geology, and climate (heat, rain, sunshine, elevation, slope, aspect, and soil), combined with the plant’s genetics, create a unique flavor and characteristic fruit in an area. This unique individuality of flavor is called “terroir” from the French “terre” or land.

A sunny spot with warmth and air circulation is a must when growing either table or wine grapes. South, southwest, or westerly-facing slopes are generally the best heat producers.

Grapes are trained on wires or trellises (different systems for table and wine grapes are used) and generally planted in north/south facing rows. Spacing between rows should be about 8 or 9 feet so that the 6-foot-high vegetation will not shade the adjacent row except early or late in the day. Individual plants can be planted 4 to 6 feet apart.

Grapes prefer well-drained, sandy, or gravelly soils for heat retention. Well-established plants can’t be transplanted, so choosing your site and preparing the soil thoroughly before planting is important.

If possible, cultivate the area where you will be planting the year before, get a soil test to determine any soil nutritional deficiencies and correct them. Make sure the area is weed-free before planting your vines.

To maximize soil heat, avoid areas prone to early spring frost or in a valley where cool air accumulates. You can plant your vines on a mound surrounded by stones to increase warmth near the plant roots. Grass growing near vines can lessen the vigor of the plant's growth, so removing the grass is beneficial.

Plant grafted grapes to promote early ripening and better resistance to root diseases. It is extremely important when planting grafted vines that the graft is planted well above the finished soil level. The vine will settle in the dirt, so factor this into your planting depth.

Apply organic matter to the soil before you plant in the spring or fall. Compost can be worked into the entire area, not just each hole. Organic mulches cool the soil, so avoid using them. Dark-colored gravel or rocks warm the soil and keep weeds down. Dark-colored poly mulches can be used, but if you have voles, be aware that they will likely find shelter under the plastic layer.

It may be necessary to use low nitrogen fertilizers after the first year because grapes can grow aggressively and deprive the soil of nutrients. An annual application of lime or sulfur-potassium-magnesium with micronutrients can be beneficial to raise the pH to the desired 6.8-7 range.

Irrigation is especially important in the first two years while your vines establish themselves. Pruning and training canes is dependent on whether you are growing table or wine grapes and can vary slightly with every grape variety and the age of your vines. For more information on trellising and pruning, look up the “Study of Grapes and Wine with WSU” at the Viticulture & Enology (https://wine.wsu.edu/extension/grapes-vineyards/), or Oregon State University’s “Growing Table Grapes” publication at https://extension.oregonstate.edu/catalog/pub/ec1639

It will take two to three years before your first harvestable crop and five to six years for grapes to reach full production maturity. Plants have been known to live for 50-100 years with proper care.