Climatic condition at a temperature below 0 ° Celsius. In general, the air temperature is measured at a height of 1.25 meters above the ground; At this altitude, the temperatures are always slightly higher than on the ground. In meteorology, frost at the level of the ground is called ground frost . Basically, a distinction is made between radiation frost and adjective frost . Radiation frost occurs on dry, clear nights with no wind, when lack of clouds, mist or haze escaping from the ground or the plant tissue heat escapes unhindered into the atmosphere. The coldest (and heaviest) air sinks to the bottom and collects on the surface, preferably in low-lying hollows. The adjective (aka "attached") frost is caused by the inflow of already cooled air from other places. This can be done from very distant areas such as through a long valley.
Even when creating the vineyards can be achieved by appropriate measures a certain protection. A hillside, from which the cold air flows into deeper areas (air drainage), as well as high education forms are of great advantage. Low-lying and flat areas are the most vulnerable. A frost control in the vineyard is done by so-called wind machines (or even by helicopters), with which a mixture with the warmer in the upper layers of air artificially induced (see also wind ). Also warming smoke ovens, large heaters and similar means are used. Artificial irrigation can be used to directly heat the vines and the soil, because when the water freezes, heat is released or a thin layer of ice on plant parts additionally forms a protective sheath.
In the northern hemisphere, frost is generally referred to as late frost in the spring (also maifrost in the month in question) and early frost in late summer / autumn. In the course of the annual growth cycle is the appearance of frost for the Rebstock different dangerous. In the northern part of Europe usually starts in April of the expulsion in which the boys shoots are particularly susceptible to late frosts. Even temperatures as low as minus 1 ° C at the level of the vines usually cause damage. Especially short-term temperature changes are dangerous if the bud after a warm spring and after a late frost occurs. Interestingly, this is not so common in the cool growing areas, but rather in warmer areas and is, for example, in the US state Texas feared. Traditionally frost-prone areas include chablis and Champagne; In 1991, one third of the crop was destroyed. By a late one pruning the shoot-out time can be slightly delayed (1 week to a maximum of 10 days).
The resistance of the vine depends on the grape variety and above all on the wood maturity. The documents are mostly cold-resistant than the tops of the species Vitis vinifera, In frost-prone areas is recommended the Bestocken with late expelling grape varieties, which are for example Cabernet Sauvignon. Clairette. mazuelo. Monastrell. Müller-Thurgau. Trebbiano Toscano. Riesling. Sauvignon Blanc and Sylvaner, Particularly at risk are, for example, the early sprouting varieties Chardonnay and Pinot Noir (but these are the best in cooler areas). Grape varieties in cold areas with frost hard winters have one resistance (Resistance) developed against frost. In the breeding This is also one of the main breeding objectives for new grape varieties. The frog-resistant Asian species will be happy to do so Vitis amurensis used. A well-known breeder of froz-resistant varieties was the American Elmer Swenson (1913-2004).
Winter frosts below 18 ° C lead to damage to the main eyes, then to the destruction of the secondary eyes and also the trunk. The danger of late frosts generally applies to the so-called Eisheiligen (11 to 15 May) as spellbound, then they are extremely rare. In late summer and early fall, early frosts can cause more or less damage. Even a few degrees below freezing point can end the vegetation and the Defoliation the vines lead. But it is of crucial importance, whether the frosts before or after the vintage occur. If the grapes have already been harvested, that's usually not so bad. Whether damage occurs in grapes that are still unharvested depends on the state of ripeness (see also under maturation ).
In unripe grapes, the harvest can be significantly decimated, the wines can thereby also a Frost taste respectively. The fully ripe grapes, on the other hand, practically do not harm frost. Temperatures from minus 7 ° C are for the production of Eiswein even unconditional requirement, but the grape harvest does not take place until November at the earliest. During the Hibernation However, the vines are relatively insensitive and survive usually short periods of cold to minus 25 ° C and more, if not preceded by several warm days, the juice have rise. In the case of vineyards at high altitudes and in high latitudes, winter frost can cause considerable damage. See also the keywords under this topic irrigation. soil type. drought. hail. climate and precipitation,