The word “terroir” is a fancy word which in the life of grape growing can pack a powerful punch. Merriam-Webster defines the word as “the combination of factors including soil, climate, and sunlight that gives wine grapes their distinctive character.” After all, the mineral notes and flavors that dance on our palates when imbibing in some really good stuff are caused by the soils in which the fruit is nurtured and grown, right? Well, not exactly.
Contrary to popular belief, soils are not directly responsible for the wonderful flavors reflected by each swirl and swig we experience. Soil influences vine growth and grape production, and thus indirectly adds the flavors we most value. That said, it’s important to understand what soil types have a positive effect on vine and grape growth, which, in turn, lead to the pleasant wine tasting and bouquet experiences we’ve come to enjoy. So, let’s explore some of these very important “wine soils” necessary for this wonderful fruit to be at its best in the glass.
Grapevines and their rootstock can grow in certain soil conditions, but fertile soil is not necessarily one of them. It’s very complicated, since pH levels, soil texture, nutrients, compounds and chemical elements residing in soil play such a big role as influencers of great wine. Drainage, structure and depth are all physical properties of good quality soils. There’s really no perfect soil that fruit farmers can point to when describing the perfect storm for vine production and grape growth. What viticulturists do know is soil needs a balance between free draining and moisture retention that will deliver the proper amount of water and nutrients needed by the vines’ deep roots. The proper soils also have a tendency to hold a certain amount of heat, which is extremely important during those cold nights. So, what are the best soils for grape growth, which enhance the flavors of our best wines?
Silt soil is very granular with a mixture of fine grains and sand. There is a nice balance of heat and water retainage, allowing for the vines’ deep roots to absorb much-needed nutrients. But this type of soil erodes easily, and thus, it’s challenging for the vines to take root.
Sandy soil allows the vines’ roots to take hold more readily than silty soil noted above. Sandy soil also has a good amount of porosity to it and will retain heat easily, but as important, this type of soil drains water quickly, perhaps too much. Although sandy soil is something of a good friend to the grapevines, it may not retain enough moisture to allow nutrients to reach and feed the fruit.
Clay soil’s structure includes small particles of clay. This type of soil can retain a much better ratio of moisture than sandy soil, but doesn’t drain well, and can drown the vines’ roots by not wicking enough water back into the ground.
Another type of soil ideally found in growing grapes, and indigenous to the California appellations of Sonoma and Napa, is a loamy soil type. This is made up of a clay, silt and sand combination. It’s ideal due to its balanced moisture content and good drainage qualities, as well as its perfect nutrient absorption rate.
So, soil types can add to the aromas and flavors of wines, but only indirectly through moisture and nutrient absorption, among other processes. By delivering the quintessential punch between organic compounds, soil texture, water and nutrients, this combination will help develop the fruit flavors into something special. It’s important to note that there is no proven direct effect between soil minerals and the mineral flavors found in the scent and tastes on our tongues.
The type of soils found in vineyards today will certainly influence the flavors of wine, but only to the extent of the grapes’ chemical and physical compositions and properties. The earthy and mineral aromas and flavors in wines really do exist but are developed through the fruit itself, coupled with grape growth, production and the vinification method. The whole process remains a beautiful and quasi-mystical experience, regardless of the way this herbal essence finds itself into our stemware. Cheers!