Grapevines grow well in home gardens, as long as you pay attention to soil health. Healthy soil creates healthy grapevines which are able to resist disease more easily and produce abundant, delicious fruit. Many commercial grape growers have turned their attention to creating sustainable, healthy, organic soil so their wine develops the character of the soil on which it is grown. There are several types of soil to consider in grape growing.
Optimal soil for grape growing is well-draining sandy loam with a pH of 5.3 to 6.0. Loam is garden soil with average organic content. Soil that is sandy without adequate organic content drains too quickly and water is not available for grapevine roots. Sandy soil consists mainly of rock and shale particles that do not provide the environment for necessary microorganisms to grow and reproduce. These are present in decaying plant and animal residue. Sandy soil benefits from the addition of composted materials so grapevine roots have particles to hold onto and develop.
Heavy clay-like soil does not allow grape vine roots to spread and develop. Water does not drain well in clay soil, encouraging root damage. Clay soils have more organic matter content than sandy soils but they do not have enough to create optimum growing conditions. Clay soil is easily amended by the addition of both sand and humus (decayed organic matter). Compost added before grapevines are planted improves soil structure and brings the pH closer to the desired level. Composted materials can be used as mulch during the growing season, which adds organic matter to the soil slowly. The University of New Hampshire Extension recommends using well-rotted manure, peat moss or a green cover crop to amend clay soil.
Organically Managed Soil
Grapevines planted in sustainable, organic soil produce healthy fruit. John Williams, of Frog Leap Winery in California recommends, in an article for University of California, Davis, organically cared for soil because “A healthy soil enriched by the organic matter of compost and cover crops and left alive by avoiding toxic herbicides, fumigants, nemadocides, and the like, is the building block of great wine." Home gardeners growing grapevines can enrich soil with compost to increase the biological activity that produces healthy plants. Biological activity produces the nutrients that increase flavor of the grapes.