Everyone knows that grapes must be properly prepared for the cold, but not everyone realizes that winter hardiness depends on the condition of the bush. In this Article: What Factors Affect Freezing, How to Increase Hardiness, and How to Cover Grapes to Overwinter Without DamageCommunity Q&A.
In the previous article “Smart Vineyard: The Basics of the Basics” we talked about the fact that there are winter-hardy varieties, that is, those that are not even necessary to cover for the winter, and those that do not tolerate the effects of frost well and require reliable shelter. Eyes of winter-hardy grapes can withstand temperatures of minus 12-15 degrees on average for a long time, and 20 degrees below zero for one to two weeks. Perennial wood of such varieties is able to withstand a decrease of up to minus 27 degrees. It should be noted that these indicators are typical for bushes in good condition, that is, with powerful roots and well-developed ripe vines..
Practice shows that no matter what winter hardiness indicators the variety has, if the grape bush is overloaded, sick or suffers from a lack of moisture, sunlight and heat, then even well-covered, it will freeze and lose young vines, which means the next year’s harvest … In this case, the main rule should be understood – the winter hardiness of grapes is always determined by the condition of the bush. Let’s see what needs to be done to increase the resistance of grape bushes to frost.
Why does the bush freeze
Almost the entire actively growing part of the root system (thin roots and root hairs) dies off in winter and gives up its substances to thicker roots. Only the part that has managed to stiffen remains alive, that is, the roots are no thinner than 1–1.5 mm. In the spring they will sprout again in thin layers, and the development of the root system will continue..
For the normal development of the roots, it is extremely necessary to have a sufficient amount of nutrients, which are given to the aboveground part of the grapes during the deterioration of conditions to overcome stressful situations (dry wind, sudden temperature fluctuations, severe frost). If in the summer the bush was overloaded, hurt, or lacked heat, the roots will not receive enough nutrients, which means that in winter they will not be able to help the grapes survive the frosts. Experienced growers believe that in order to protect the roots, it is necessary to mulch the soil in the vineyard. Organic mulch will be useful for all varieties, as it can protect the earth from rapid freezing.
The most lively and delicate parts of the bush are the eyes, they live, breathe and evaporate moisture constantly, except for the freezing time. Three factors can threaten the grape eyes. First, there are sharp jumps in temperature from warm to frost, which usually occurs on clear nights and is accompanied by the appearance of frost. Practice shows that in this case, the endurance of the kidneys is significantly reduced. Secondly, frosty temperature, accompanied by a dry wind, can greatly harm the eyes. Under such conditions, the vines are very dry, and the freezing of the eyes is accelerated. The third dangerous factor for the kidneys is long-term icing of the vines. The eyes will withstand a day under a layer of ice without problems, but then there is a danger that they can suffocate.
Bushes of resistant varieties with mature wood and a developed root system will survive the winter without problems. However, it is not always possible to plant such a variety, and the taste of the fruits of such grapes is much inferior. Therefore, experienced specialists have developed a number of rules to make the bushes already in the vineyard as winter-hardy as possible..
How to increase winter hardiness
As we have already found out, healthy, well-developed grapes with strong roots survive the cold best. In order for the bush to develop well, it is necessary to follow certain care rules during the season, which will increase the resistance of the vine to cold weather:
- First of all, you need to pay special attention to that moment in order to provide the grapes with an optimal load. We described how to do it correctly in the article “Smart vineyard: shaping on a trellis or arbor”. An overloaded bush does not develop well, since all the forces are spent on ripening the bunches. Such grapes do not allow the roots to stock up on the necessary amount of nutrients for wintering. An underloaded bush throws out powerful fat vines, but they will not be distinguished by good frost resistance, since practice shows that the most resistant to cold are vines of medium strength, which received maximum sunlight over the summer. Therefore, it is necessary to load the bush so that there are as many of them as possible..
- There is no doubt that grapes can ripen in the best way only in the sun, even with the slightest shading, the vine does not develop normally – the wood of such a bush will be watery and loose and will not be able to accumulate the necessary nutrients.
- To increase winter hardiness, it is recommended to make sure that the grapes do not get sick throughout the season. The most dangerous disease in this sense is mildew, which causes leaf dieback. And if the leaf dies off, this provokes the growth of stepsons from sleeping eyes. Such shoots, as a rule, do not ripen until autumn, and the vine can die from the first frosts in November..
- Proper nutrition will help increase resistance to cold weather. As you know, potassium is the main anti-stress substance for grapes. Therefore, experts recommend adding wood ash under each bush during the season (on average, a bucket per season). But grapes overfed with nitrogen will be very pampered and will give fat and bursty shoots that are unlikely to withstand severe frosts.
- A properly moistened soil under it will help improve the frost resistance of the bush. Dry ground cools down and freezes very quickly, while wet ground has a high heat capacity and smooths out the negative effects of low temperatures for a long time. In addition, the eyes need moisture for normal breathing and development. However, it should be noted that it is necessary to start moistening the soil under the bushes in October-November, and in no case should the grapes be poured in the middle of summer, since frequent watering at this time can provoke the growth of young shoots that will not have time to mature before winter. Well, what is the risk, we have already discussed.
So, from all of the above, it is clear that in order for grape bushes to be able to better resist frost, it is necessary to give them an optimal load, provide maximum sunlight, protect against diseases, and also feed and water properly..
How to shelter grapes for the winter
The grapes growing on most household plots either do not hide at all, or are diligently buried in the ground. There are simpler, but equally effective ways. Let’s take a look at some of them.
For example, you can simply pull the bush off the gazebo, cut it off, heap it up and lightly cover it with earth. Various homemade hooks made of reinforcement or thick wire will help to pin the grapes to the ground. Experts believe that it is enough to cover a bush pressed in this way with a layer of earth of 3-5 cm. The main danger for grapes in winter is strong dry winds at low air temperatures, and if your bushes grow in a windless place, then you can not sprinkle them for the winter – just press it to the ground. Also, in this case, instead of land, you can use various improvised materials – corn stalks, straw, weeds. It should be noted that the wetter the soil to which the grapes are pressed, the less the risk of freezing..
Many believe that it is impossible to cover the grapes with a film – it will get worn out. It’s a delusion. You just need to wrap it up not tightly so that the air circulates freely. The film can be used to cover both trellis bushes and bushes on the gazebo.
The grapes growing on trellises must be cut off, put on the ground, covered with a film on top, which is pressed down along the edges with pieces of earth. Gazebo bushes that need to be covered must be bundled and freely wrapped with pieces of polyethylene – in this form, leave directly on the gazebo.
Well-developed and matured high-stamped bushes on trellises can not be lowered to the ground, but wrapped in foil right on the spot. The basic rule in this case is that the winding should not be airtight and tight, so that on sunny winter days the grapes do not overheat and suffocate. It is necessary to wrap with polyethylene freely, leaving small gaps for ventilation. Some experts use roofing material, tarpaulin, rubber, as well as specially made boxes of boards to hide grapes..
When preparing grapes for winter, the question may arise: when do you need to cut the bushes? Experts recommend that those bushes that require shelter be cut in the fall, since it is quite difficult to work with uncut ones. But those that you do not plan to wrap up should be pruned in early spring before the start of sap flow, since practice shows that uncut uncovered grapes are better able to withstand low temperatures..
When preparing grape bushes for winter, you need to understand the main thing – well-ripened healthy grapes will endure unfavorable winter conditions much easier. Therefore, the main task in this case is to create optimal conditions for the growth and development of the bush throughout the season. The correct load, maximum heat and sun, protection from diseases, as well as optimal watering and nutrition will allow the grapes to retain more vital energy and more easily survive the winter..