While many wine lovers get weak-kneed when they see limestone, or wax lyrical about granite, schist or slate, few get as excited about sandy soils. It’s partly because we want to see rocks in our vineyard, and sand lacks drama. However, there are advantages to growing wine grapes in sandy soils.
Defined in various ways, sand is one of three particle sizes in soil. The others are silt and clay, and loam is a mixture of all three. Generally, the diameter of coarse sand measures 0.2–2 millimeters, and fine sand ranges from 0.02–0.2 millimeters. Silt is 20–2 micrometers (.02–.002 millimeters), and clay is less than 2 micrometers (.002 millimeters).
Due to the size of these particles, sandy soils are very porous. As a result, water can infiltrate and pass through these soils easily. Well-drained soils generally benefit grape vines, but they can also lead to drought stress if roots aren’t deep enough to access water reserves.
Sandy soils tend to have low levels of organic matter, which means they can lack fertility. Many winegrowers use compost or plant cover crops like fava beans or oats to try to increase the organic matter in sandy soils, which also makes them better able to retain moisture.
Arguably the most famous sandy site for wine pilgrims is Vassal, France, where centuries-old vines feature nearly 3,000 grape varieties from more than 50 countries. Phylloxera, the root-munching aphid pest that almost destroyed viticulture in the 19th century, can’t grow on sand. So, in 1949, French agriculturists moved a collection of 1876 cuttings to Vassal, where vines can grow on their own roots without the need for pricey rootstock or labor-intensive grafting.