Creepy but Harmless: Grape Aerial Roots

Aerial roots on a grapevine in eastern Minnesota. 
Photo: Annie Klodd

Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production

I receive about 12 calls, texts, and emails throughout the year from grape growers and home gardeners who have spotted a somewhat disconcerting anomaly on their grapevines.

The question usually goes something like this: "Hello Annie, I have found these weird finger-looking things growing out of my vines. What are these? Are they a problem?"

These long, skinny red structures, which grow from the trunks or limbs (cordons) of the vines are called grape aerial roots.

Why is my vine producing grape aerial roots?

Grape aerial roots, in themselves, are harmless. There is no evidence suggesting that they will impact the health or fruit production of the vine. However, grape aerial roots may actually be a sign from the vine that it is stressed or that it has experienced injury in the recent past.

Eric Stafne, a horticulture professor at Mississippi State University, has written an Extension article describing aerial roots. He explains that while the causes of aerial roots are not thoroughly understood, they are more commonly found in humid conditions, tropical regions, greenhouses, and in temperate climate where vines experience winter injury. I frequently observe them in vineyards that have wet soil or very humid canopies.

Grapevines growing in Minnesota regularly experience winter injury and heavy rain, so it makes sense that so many grape growers report seeing aerial roots. A 1999 study found that a wound on the vine (like winter injury) is necessary to stimulate aerial root growth.

How to respond to aerial roots

If you have a grapevine with aerial roots that is also exhibiting die-back or is not producing much fruit, the failure of the vine is likely due to winter injury, disease, "wet feet," or other environmental stresses.  It is not due to the aerial roots. The aerial roots are likely just a benign consequence of the stress that the vines are experiencing.

Treat the aerial roots as a clue that the vines may be stressed. Assess the impact and cause of the stress, and respond accordingly:

• If the vines are producing well, no special action is needed beyond your regular management practices.
• If the vines are frequently unhealthy, evaluate whether they are growing in chronically wet conditions. Avoid irrigating mature vines, and plant new vines in areas with better drainage. Sometimes, growers will even install drainage tile, or transplant vines from waterlogged areas to better sites when they feel it is economically feasible to do so.
• Evaluate whether there is frequent die-back on the vines, and whether you are growing a variety that is known to be hardy in your area. Winter injury is a major cause of grapevine die-back in Minnesota. Severely winter-injured or dead cordons can be removed and replaced, using new canes from the center of the vine.
• Consider that winter injury is often worse in wet, low-lying areas.

As far as we know, there is no reason to remove the aerial roots. They will dry up on their own.

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References: 
de Klerk, J-G., W. van der Krieken, and J. C. de Jong. 1999. The formation of adventitious roots: New concepts, new possibilities. In Vitro Cellular and Developmental Biology – Plant 35:189-199.