winter protection for grapes Archives

Spring Frost Damage On Grapes

Spring frost damage is a common problem among grape growers!

 

spring frost damageAs you can see from the picture on the left, spring frost damage on grapes can cause severe damage and if you grow your grapes in colder climates, you will sooner or later have to deal with spring frost damage.

What makes spring frost damage a big problem is that preventing it, is not easy – economically and practically.  Some years you will have no spring frost damage and another year you can loose all your grapes due to spring frost damage.

Even here in South Africa, where temperatures are known to be mild to hot, we sometimes face dangerous Spring temperatures and many grape growers in the lower region of where I live, have suffered crop losses because of spring frost damage.

Most grape growers from the US who grow their grapes in climates colder than zone 6, will definitely know what I’m referring to.

When will spring frost damage occur on grapes?

Generally, there are two type of spring frost.  Advective and radiattion frost.

Radiation frost damage happens with clear night skies and calm airflow or wind conditions.  With clear skies, radiant heat from the earth moves up into the upper layers of the atmosphere and the calm wind conditions allow the air to mix.  An inversion occurs where the a layer of cold air is trapped below the layer of hot air from the dadiation.

Advective frost happens when a cold front moves into an area with gusty winds trapping the cold air on at ground leve.

Spring frost damage – what happens inside the grape vine?

I will not dig too deep into the physiology of the grape vine, but spring frost damage occurs when the water inside the plant cells of the grape vine cools down to temperatures below freezing.  Ice crystals form and damage the cell membrane of the plant cells, causing the sap flow to escape from the plant cells once the temperatures increase.

Choosing your site to prevent spring frost damage:

The most important factor that will influence spring frost damage is your site location – not even planting the correct variety, or using the correct pruning methods will fully safeguard your grape vines from spring frost damage.

Cold air is heavier than hot air and will form pockets of cold air in valleys, near rivers and even alongside a tree lines.  Avoid planting your grape vines on these location as far as possible; especially if spring frost damage is a problem in your area.

Planting your grape vines on a down slope, will force the cold air to move away from your grape vines, into the lower areas of the land – this could help prevent spring frost damage!.

Trellis & training systems to help prevent spring frost damage

As said earlier, cold air is heavier than hot air, so the temperature close the surface of the ground is colder than a few feet higher.  Using a higher trellis system could make the difference between light and severe frost damage.

Cultivation practices to help prevent spring frost damage

Here are a few tips that might just save your grape crop from spring frost damage.

  • If you grow grapes on a larger scale, it is advisable to get a frost alert system in place.
  • Keep your eye on the calendar for historical frost damage dates.  Knowing historical spring frost damage dates can help you plan ahead with irrigation or to cover your vines.
  • Use a cover crop on your soil and keep away from bare soil cultivation.  Bare soil will loose it’s latent heat much quicker than soils covered with organic material.
  • Manage your irrigation correctly – drought stressed grape vines are more susceptible to spring frost damage
  • Prune as late as possible.  Pruning later will prevent the basilar buds from opening too soon.
  • Use cane pruning method.

What to do after spring frost damage occured:

Come to terms with your losses – you will have a lighter crop but not necessarily no crop!

Do not cut off the damaged parts too soon.  A grape vine has a composite bud, meaning there are 3 buds within what looks like a singe bud.  Chances that the secondary and tertiary buds will open after spring frost damage is good.  These buds can produce grapes as well, although not as many as the primary bud.

If only sections of the shoots are damaged, new growing points will appear from buds situated near the base of the shoot.

 

All I can say; loosing your grapes to spring frost damage can happen within a few hours.  Keep a watchful eye on the weather channel and try identify climate conditions that may lead to spring frost damage.

Good luck my friend and hopefully your grape vine will have a better chance to survive the next spring frost!

Danie – The Grape Guy

www.my-grape-vine.com

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Winter Protection for grapes

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!