What is winter hardiness of grapes defined by?
Winter hardiness of grapes depend on a number of circumstances, and first of all - on conditions of its cultivation, a damage rate by wreckers and diseases, time of the end of growth of escapes, their ripening, on nature of training of plants during the autumn period and depths of rest.
During the summer period of a plant there pass several phenophases, forming the wintering bodies with a certain reserve of nutrients, that is even long before approach of low temperatures they prepare for wintering. Various bodies of a grape bush have not identical resistance to low temperatures. Roots of a grapevine are less frost-resistant in comparison with elevated part of a bush. For example, at the European grades roots die off at a temperature minus of 5 - 6 degrees, at American - at minus 12. Are more frost-resistant evropeysko - the Amur hybrids.
At the European grades of grapes without shelter for the winter eyes are damaged at decrease in air temperature to minus 18 - 20 degrees, one-year escapes - at minus 21 - 22, long-term wood - at minus 24 - 26 degrees. The damage rate of elevated part of a bush in many respects depends on duration of influence of low temperatures, biological features of a grade.
At the end of summer and during the fall in a grapevine there take place three main physiological processes causing preparation it to wintering - the timely termination of growth of escapes, transition of the wintering kidneys and a cambium in a condition of organic rest, ripening of fabrics of escapes, a hardening. The dormant period plays a huge role in frost resistance of grapes. Organic rest is an ability of kidneys not to sprout in the fall when activity of root system still continues.
For the correct hardening of a grapevine decrease in air temperature has to be gradual in the fall. Damage of a rod by a frost in several degrees seems impossible: in the winter it maintains much lower temperatures. But early frosts often damage eyes and reduce future harvest as the rod does not manage to pass the training increasing frost resistance of a plant by this time.
During the winter period fast changes of temperature are very dangerous to a grapevine. Thaw causes renewal of growth processes in fabrics, from - for what they easily are surprised even small frosts.
In the district where winter temperatures fall below minus 15 degrees, it is necessary to cover slabomorozostoyky grades of grapes carefully. It is necessary to make it right after the first weak autumn frosts. If with it to tighten, then not to avoid damage of a rod. Because after hit under frosts it becomes very fragile and easily breaks and bursts in attempt to lay it on the earth.
Depending on local climatic conditions bushes cover in whole or in part hill. For this purpose take moderately damp friable soil, but not directly from - under a bush not to bare roots. The most important - to cover a pristvolny circle with a diameter not less than one meter. For its mulchirovaniye use the soil, the rerotting manure, peat, straw. The rod is bent down to the earth and carefully cover with fir-tree fir twigs, straw, sawdust or foliage a layer not less than 30 cm. It is impossible to cover bushes with a film. In the period of thaw escapes under it heat up and kidneys resume growth, and with return of cold weather are easily injured.
I hope, this information will help you to make correctly the grapes ready for the winter. Good luck and good harvests!