How to you protect your grape vines from the cold?

If you are in the unfortunate position to live in an area with constant sub zero temperatures, it is important to take note of this article.

Most of you people in the USA are nearing winter now and your grape vines will be preparing itself for the winter (dormancy). The leaves will turn their color and will fall, exposing only the canes and old wood on the grape vine.

The grape vine going dormant doesn’t mean you as a grape grower can go dormant as well! There are lots of work to be done before the real winter starts, so therefore I decided to prepare you for this winter by giving you some tips on how to protect your grape vine from cold damage.

Now you might be asking yourself: “What will a guy from South Africa know about cold damage?” and yes you are absolutely right, the temperatures in the far north drop much lower than here down south, but that doesn’t mean I know nothing about the prevention of cold damage! :-)

Okay, lets look at winter protection for grapes.

Protecting your grape vines from cold damage starts when you plan your vineyard or when you decide to buy a few grape vines. Carefully planning the location of your vineyard and choosing the right variety is probably the most important steps you can take in preventing cold damage.

As soon as you have harvested the grapes from your vines, no more carbohydrates is send to the canes of the vines and will start going dormant and prepare it self for winter (hardening off). The earlier this happens, the more time there is for the grape vine to harden off and the more resistant it will be to extreme cold weather.

In other words, if you live in an area where early frost is a problem, you should choose a variety that ripen early in summer, so your grape vine will have enough time to go completely dormant before the frost.

Both internal soil drainage and external air drainage are very important. Cold air is denser than warm air and tends to sink and flow down hill just as water does. Vineyards must planned beforehand and planted on sites where cold air is deflected, and any barriers to movement of cold air out of the lower side of the vineyard should be eliminated. Low areas and flat areas collect dense cold air. These should not be planted to cold sensitive varieties. These low areas were cold air accumulate, we call cold pockets and this is normally where the most cold damage occur.

Now what cause the damage on the grape vines?

The whole grape vine consist of plant cells filled with sap and if the temperature drop below the freezing point of the sap inside the cells, will freeze and eventually kill the cells. Most damage on grape vines occur near ground level where it much colder than a few feet above the ground, so protecting the trunk of the grape vine in very cold climates is imperative for the survival of your grape vine. This is especially important during a cold, still, clear night when heat is radiated rapidly to the dark sky and the temperature near the ground drops dramatically.

During mid-winter spells of above 32 degrees Fahrenheit, the biochemistry of the grape vine will change and might cause the grape vine to temporarily de-harden making it susceptible to a sudden drop in temperature. It is therefore important to cover the trunk of the grape vine during relatively hot winter days (as strange as it might sound!).
Burial is a most practical solution. In very cold regions, whole vines are buried. The most common practice is to “hill-up” the vines with a mound of earth in the fall. The earth should cover the graft union to ensure that some scion buds will survive if the above ground tissues is damaged. Remember to remove the hill once the danger of cold damage is over, otherwise scion roots will develop from the scion and will counter effect the advantages of having a rootstock.

The effect pruning can have cold damage. It is a well known fact that pruning stimulates the grape vine and will almost “force” the vine out of dormancy earlier. In areas where early spring frost is a problem, you should prune very late – even after the first signs of bud break is visible. The buds furthest on the canes of a grape vine will normally break first, because it will be the gathering point of newly transported carbohydrates that reached the end of the canes. If the buds at the end of the cane is damaged by a sudden spring frost, the half dormant buds near the old wood, will most probably survive the cold. You will notice, that as soon as you prune canes that has sprouted on the ends, the buds left on the vine will start sprout almost immediately.

Another method some grape growers in the very cold areas use, is to have multiple trunks on their grape vines. If cold damage kills one trunk of the grape vine, another one can produce a crop the coming summer, so no total crop loss will occur (except if both trunks are killed off course).

These are some basic tips when you prepare your grape vine for winter, so get to work before the winter cold hits your area.

Good luck!