What is Grafted Rootstock and What Role Does it Play in the World of Wine?
If you’re an avid gardener, you may already know about the use of grafted rootstock to propagate plants.
From a big-picture perspective, grafted rootstock is used in plant propagation to combine the strengths of two different plants into one. The rootstock (the lower portion) is selected for its hardiness, disease resistance, and ability to adapt to specific soil and climate conditions, while the upper portion (scion) is chosen for its desirable fruit, flower, or foliage characteristics.
By grafting them together, growers can produce plants that are more resilient, productive, and consistent than those grown from seed or cuttings alone.
I grow Vitis vinifera grapevines, in particular Pinot Noir and Riesling. Till this year, I’ve always used grafted rootstock when planting new vines.
Why use grafted rootstock?
Because Vitis vinifera vines are very vulnerable to a pest called phylloxera, a root-feeding insect that devastated vineyards across Europe in the 19th century. Most modern vines are grafted onto rootstocks derived from resistant American grape species, which protect the plant while allowing the scion to produce the desired grape variety, i.e., Pinot Noir and Riesling.
Another way to propagate grapevines is through cuttings.
Propagating a grapevine from cuttings is the other, more reliable propagation approach. A cutting creates a new plant from taking a section of an existing vine—typically a piece of dormant, one-year-old wood—and encouraging it to grow its own roots. The new plant will be genetically identical to the parent.
For the first time, I decided to use cuttings this growing season to fill several gaps in the vineyard. The process is fairly straightforward, doesn’t cost much, and, supposedly, vines grow faster from cuttings.
As I pruned the vines in early March when they were still dormant, I took a dozen promising vine cuttings. I dipped each cutting in a growth hormone solution and placed it in a growing medium of loose soil. They now sit in a bright window, sheltered from the outside elements.
In theory, the next two months should bring roots in the growing medium, possibly a few shoots with leaves above the soil level as well.
As you may have already surmised, there is a risk in using the cuttings. Phylloxera exists in the valley, though it is isolated in certain areas. (See the photo of a grape leaf infected with phylloxera below.) My hope is that a dozen vines grown from cuttings, intermixed with 110 vines on resistant rootstock, should reduce the risk.
Further, I will tag the new vines once they are planted so they can be tracked over time. In the future, should they succumb to the louse, I’ll remove them in favor of grafted rootstock.
In the meantime, I can track the development of vines grown from cuttings in the vineyard and compare them with those on grafted rootstock, noting similarities and differences.
There is always science to be had!