Protecting grapes from frost
Frost resistance and winter hardiness of grapes characterize the ability of this plant to withstand adverse temperature effects in winter, spring and autumn. The ability of grapes to withstand, with no signs of tissue damage, temperatures below 0 ° C during winter frosts and short-term frosts characterizes its frost resistance. It is determined by the origin and biological characteristics of the variety, the degree of maturation of shoots and hardening of wintering eyes, the condition and development of plants, the structure and moisture capacity of the soil.
Winter hardiness of grapes
In winter, the grape bush is exposed to a complex of adverse factors: low temperatures, thaws and high humidity, sharp fluctuations in positive and negative temperatures, and is also damaged by rodents.
The ability of a plant to tolerate without significant damage the impact of these adverse factors in wintering conditions characterizes its winter hardiness. This indicator also depends on varietal characteristics, growing conditions, and to a large extent on the general condition of the plants and their preparedness for winter.
The winter hardiness of a plant is affected by the accumulation of nutrients in the tissues of the vines and roots, the dormancy of wintering eyes, the degree of ripening of the shoots and the nature of the temperature decrease during autumn hardening of plants.
Varieties possess increased frost resistance: Alpha, Moscow Sustainable, Hassan Bows, Chasla Rumming.
Damage to grapes from low temperatures
Grape plants are often damaged by early fall and late spring frosts. By lowering the temperature in autumn to minus 2 ° С, leaves and tops of green shoots are damaged, and when lowering to minus 4 ° С - berries. This adversely affects the ripening of shoots and the preparation of vines for winter. At the same time, the future yield is also reduced due to damage to part of the wintering eyes.
The greatest damage to vine plantations is caused by late spring frosts. Swollen kidneys and all green shoots die from them. As a result, annual vines cannot restore the leaf apparatus and often die. Damage caused by spring frosts is restored only within a few years. In spring, when freezing to minus 4 ° C, puffy eyes die, at minus 0.5 ° C - leaves, and at minus 0.2 ° C - inflorescences, so the main task of the gardener is to protect the vineyard from late spring frosts, otherwise all efforts to grow grapes will become useless.
There are two types of frost control: biological - the cultivation of frost-resistant varieties and agrotechnical - the placement of bushes on the site in warm areas protected from the north winds, the use of film shelters and the introduction of increased doses of potash fertilizers.
The use of film shelters to protect grapes
Protecting plants from frost starts with laying the vineyard. One of the effective methods is the use of film shelters (Fig. 1). After removing the winter shelter of the vineyard, they carry out the final pruning of the vine and leave it tied in bunches on the ground. The whole ridge is covered with a frame in the form of a greenhouse with wire arches and covered with a film.
Do the same with seedlings planted in a schoolhouse or planting buckets. Care for the bushes at this time boils down to daily airing of the film shelter. If frosts are expected, it should be borne in mind that the film protects plants only at temperatures up to minus 2 ° C, therefore, with a more significant cooling, the frame should be covered with a second layer of film or any other improvised material (clothing, tarpaulin, burlap).
The shelter is removed and the vine is tied to a support when the danger of frost has passed. This method of shelter has one drawback - the green shoots under the film shelter grow very intensively and by the time the frame is removed, reach 50-60 cm in length. At the same time, they are weakly kept on vines and easily break off. Gartering the vine to the support in this case requires special care.
Dry garter of the vine to the trellis is carried out in the phase of bud germination. In this case, it is possible to save all developed shoots. However, the protection of vineyards from frost is difficult, since the presence of trellis hinders the shelter. In these cases, open heating of areas with bonfires, smoke, spraying and abundant watering of plants are used. An effective measure for plant protection is the multiple spraying of green parts with water in the early hours with an interval of 10-15 minutes and plentiful evening watering.
It is very convenient to install collapsible trellises, which have a hinge or collapsible connection at the bottom, which allows you to put a vertical trellis with bushes in the aisle and cover the bushes on the ground with plastic wrap and other heat-insulating materials.
In autumn frosts, they also shelter bushes using heat-insulating materials, but the main means of protection against frosts is proper agricultural technology in the summer and autumn: stopping irrigation, using phosphorus-potassium fertilizers, chasing shoots, timely harvesting, and water-charging irrigation.
In order to protect the grapes from frost, a winter shelter of ground parts and fruit vines is carried out. Depending on varietal characteristics, light or double shelter of bushes is used. It is carried out in several ways: by hilling the head and vines of the bush with loose and moderately moist soil; using special boxes and insulating materials.
The most important condition for the good preservation of the eyes in the winter is that when the shelter is covered, the vine is dry.
Otherwise, by spring, the vines become moldy and the eyes die. It is necessary to cover the bushes immediately after weak autumn frosts, which are observed, for example, in the Moscow Region in late September and early October.
Before sheltering the vine is removed from the supports, pre-pruned and tied in bundles that are laid along the rows. Young vine bushes for winter shelter earlier than fruiting.
When hilling with earth, they cover primarily the head and sleeves, as well as 4-5 eyes on annual shoots. After hilling, the bushes are covered on top with a film or roofing material, the edges of which are spudded with earth. To avoid damage to the root system, the ground for earthing up is taken at a distance no closer than 60 cm from the head of the bush.
Dry grape shelter for the winter
In the Moscow Region, the so-called dry shelter is successfully used, in which the bushes are covered with wooden gable ducts (Fig. 2).
With such shelter, the vine is also tied into bundles and pinned to the ground. Softwood branches (lapnik) or boards are placed under the harnesses. Then the vine is covered with boxes hammered together from a tez. The air between the walls of the box and the ground is sufficient protection against low temperatures for frost-resistant varieties. The box should fit snugly against the soil and not let cold air pass to the head of the bush. Boxes are installed along the entire length of the row. From above they are covered with a film or roofing material.
When sheltering less winter-hardy varieties, the vines and the head of the bush are covered first with a dry sheet or needle, and then the boxes are installed and covered with a film.
In the northern regions, a two-layer shelter is advisable. With this method, a layer of straw, leaves or a needle bed is laid on the laid vines, and on top they are covered with a layer of earth and then the boxes are installed.
Instead of baskets, you can use wooden shields, but then along the edge of the rows at a distance of 40-50 cm from the bushes make shafts with a height of 20-25 cm. Wooden shields are placed on these earthen shafts, which are covered with a film or roofing material. The preparation of the vines is carried out in the same way as in the first case. In winter, in severe frosts, it is necessary to ensure that the snow cover is high enough.
Snow is the best shelter, and its accumulation in the vineyard guarantees the safety of bushes. The temperature on the surface of the soil under a snow cover of 19-23 cm is 15-16 ° C higher than the temperature of the soil free of snow. In winters with little snow, mulching the soil with straw, reeds, peat, sawdust, as well as winter irrigation and artificially built-up ice layer helps preserve the roots.
- A. Shitov - The vine in the Non-Black Earth region.