Zones of frost resistance of plants - what are and why should they be known?
More and more in the summer cottages there are new (including exotic) trees and shrubs, fruit and garden crops. Passion for exotics does not always please a summer resident, although sellers assure that the plants are zoned and able to withstand any climatic hardships. Do not always trust empty words. The zone of its frost resistance will “tell” about the prospects of plant adaptation to the growing area. What is it, and how to apply knowledge about the frost resistance zone of a plant in practice, we will describe in this article.
- What is frost resistance and winter hardiness of plants?
- Who divided the world into "zones"? Brief historical background
- Table of USDA frost resistance zones
- How to use the frost table?
- How to increase frost resistance of plants?
What is frost resistance and winter hardiness of plants?
Often, when buying plants, summer residents complain that they poorly or not at all take root, and some die after the first winter. At the same time, proper care was given to the plant and the right place was chosen. Something went wrong?
Accused of deceiving sellers. Like, "slipped" low-quality goods. But is it really the sellers are to blame? Different regions vary significantly in climatic conditions. And the first thing that needed to be done to ensure the success of the purchase was to ask about the frost resistance zone of the plant. It is possible that it is completely inconsistent with the environmental conditions in which you are going to plant your plant.
Do you know what extreme temperatures your geographic area differs from others? These data will help you understand which plants can grow and develop in your area, and for which additional cares will be needed (shelter for the winter, transfer to a warm apartment, to a closed balcony, to a winter garden or a greenhouse, growing in greenhouse conditions). It should be understood that frost resistance and winter hardiness are not the same thing.
Frost resistance - A term that characterizes the ability of a culture to tolerate extremely low temperatures in winter. That is, the frost resistance of a plant is determined by the lowest temperature that it can survive in winter without additional shelter and insulation.
Winter hardiness - the ability of plants to withstand adverse temperature and other environmental conditions. Spring thaws give way to short-term frosts. And if some plants maintain a stable twenty-degree frost easily even without shelter, then the sharp temperature jumps from -10 ° С to the "pluses" and vice versa are certain deaths for many of them.
Frozen cell sap is thawed, expands in volume and causes rupture of cells of woody tissues and plant bark. Cracks appear in which snow, water gets, and then - mold, fungal and other infectious microflora.
You can protect plants in such unstable weather with temporary shelters (the use of caps, swaddling, coniferous spruce branches, mats and other types of insulation). Helps to survive the temperature changes of whitewashing trunks and skeletal branches at the end of winter. Whitewashed trees reflect the sun's rays well, not allowing the trunks to heat up very much during the day, and at night in cold weather - to cool sharply.
All measures aimed at protecting plants from temperature extremes are called increasing winter hardiness. But their shelter for the winter - increased frost resistance.
The USDA frost resistance zones adopted worldwide for determining the frost resistance of plants do not fully take into account their winter hardiness. Therefore, they can be considered indicative, and you should not rely blindly on them.
Who divided the world into "zones"? Brief historical background
For the first time such a temperature and climate scale was developed in the United States for agricultural needs. The innovation allowed the United States to describe its territory not only in terms of temperature ranges for crops, but also to identify tree and shrub crops that can grow and develop in the ranges of these temperatures, that is, in certain areas.
They called such a breakdown into zones by the USDA scale (the first letters of the name of the USDA). Today, the regions of all states of the globe are divided into frost resistance zones on the USDA scale indicating the types of plants adapted to live in such climatic conditions.
In Russia, and earlier in the USSR, work on zoning frost resistance of plants began in the early 20th century. The temperature scale of frost resistance was supplemented by a list of tree crops (fruit and forest) found in climatic zones. The data obtained were combined by Professor A.I. Kolesnikov (1974) with later co-authors in the multivolume edition “Decorative dendrology”.
Work on zoning the territory of Russia, as in other countries, continues to this day. The main direction is zoning detailing, taking into account factors affecting the winter hardiness of plants: average annual temperatures (monthly and quarterly), average and minimum humidity of the region, annual rainfall, moisture evaporation, strength and constancy of wind (dry wind), soil type, daylight hours, dates of the first spring frosts and the first real frosts and others.
Due to additional or side factors, a microclimate is created within the climatic zone, which changes (sometimes significantly) the average temperature indicators. If side factors contribute to an increase in temperature, then plants of warmer zones can be grown in colder ones. But at the same time, all the requirements of agricultural technology and measures for sheltering plants for the winter are required.
The climate has changed today, but so far there is no more detailed climate maps in the use of agricultural, forestry and other farms than regional ones, which is not enough for individual farms. Therefore, all data used by agricultural enterprises and summer residents are considered indicative. Nevertheless, it is climate maps or other reference materials that can most accurately answer the question of whether the plant you bought will survive in the winter and what conditions it will require to survive.
Table of USDA frost resistance zones
|0||a||−53.9 ° C|
|b||−51.1 ° C||−53.9 ° C|
|1||a||−48.3 ° C||−51.1 ° C|
|b||−45.6 ° C||−48.3 ° C|
|2||a||−42.8 ° C||−45.6 ° C|
|b||−40 ° C||−42.8 ° C|
|3||a||−37.2 ° C||−40 ° C|
|b||−34.4 ° C||−37.2 ° C|
|4||a||−31.7 ° C||−34.4 ° C|
|b||−28.9 ° C||−31.7 ° C|
|5||a||−26.1 ° C||−28.9 ° C|
|b||−23.3 ° C||−26.1 ° C|
|6||a||−20.6 ° C||−23.3 ° C|
|b||−17.8 ° C||−20.6 ° C|
|7||a||−15 ° C||−17.8 ° C|
|b||−12.2 ° C||−15 ° C|
|8||a||−9.4 ° C||−12.2 ° C|
|b||−6.7 ° C||−9.4 ° C|
|9||a||−3.9 ° C||−6.7 ° C|
|b||−1.1 ° C||−3.9 ° C|
|10||a||−1.1 ° C||+1.7 ° C|
|b||+1.7 ° C||+4.4 ° C|
|11||a||+4.4 ° C||+7.2 ° C|
|b||+7.2 ° C||+ 10 ° C|
|12||a||+ 10 ° C||+12.8 ° C|
|b||+12.8 ° C|
Plant frost zones, originally developed by the US Department of Agriculture, show average annual extreme temperatures (daily minimum temperature), rather than the absolute lowest temperatures observed in the region.
How to use the frost table?
For practical use, the climate zoning scale for USDA zones is convenient in the form of a table or map. In 2012, it was updated due to climate change over the past 30 years. The territory of Russia occupies zones from zero to 9th. There are 13 USDA zones in the world - from 0 to 12. Moreover, for more accurate information, each USDA zone has two subzones a and bwhose limiting temperatures vary between 2-3 ° C.
- Zone 1 - Central Siberia;
- Zone 2 - South Siberia;
- Zone 3 - Ural, Eastern Siberia;
- Zone 4 - Moscow region and most of Central Russia;
- Zone 5 - Moscow, St. Petersburg and the region, Vladivostok, the Midland of Russia, the Baltic states, Minsk and most of Belarus, Kiev and central Ukraine;
- Zone 6 - Caucasus, Krasnodar Territory, Crimea, western and southern regions of Ukraine, eastern and central Poland, Czech Republic;
- Zone 7 - The south coast of Crimea;
- Zone 8 - Dagestan;
- Zone 9 - Sochi.
In addition to weather, many other factors influence the winter hardiness of plants. Under natural conditions, plants cannot grow strictly in a certain area. For example, forest and other crops in the Novosibirsk region grow with equal success in the 2nd and 3rd zones. For Moscow and St. Petersburg, you can choose plants that will successfully grow from the 1st to 4th zone, although for them the main is the 5th zone. Only in the colder will they have to be covered for the winter, mulched, wrapped, covered with caps.
The above examples once again show that zoning according to temperature characteristics is an example and takes into account the minimum winter temperatures that the plant can withstand. When choosing which plant you can buy, you need to take into account not only temperature data, but also the local climate (amount of snow, duration of frosts, wind strength, return frosts, etc.). Certain plant species can spread within 5-6 zones with milder climates.
When buying plants in the nursery, be sure to look for the USDA zone, in addition to zoning, on the tag. To which category (group) does culture (primary, secondary or auxiliary) belong?
Our article “The best varieties of fruit crops for cold regions” will help determine the choice of fruit.
As for the exotic plants, even with the same temperature zone of growth, be prepared for their acclimatization in new conditions, which means shelter, protection from diseases and pests, and other additional work.
How to increase frost resistance of plants?
The following factors sharply reduce frost resistance and winter hardiness of plants:
- violation of agricultural care culture;
- autumn moisture deficit;
- soil type and fertility;
- long frosts with little snow;
- epiphytotic lesion of plants by various diseases, etc.
In order to increase the frost resistance of trees and shrubs, vegetables and other crops, it is necessary to keep the plants in the required conditions throughout the growing season: water them in a timely manner, feed and protect them from diseases and damage by pests. Do not feed plants in the second half of the growing season with nitrogen fertilizers, which, increasing growth, do not allow young shoots to mature.
Autumn water-loading irrigation (if necessary) should be sufficient. The depth of the wetted layer under the trees is at least 0.7-1.0 meters, under the bushes - 0.2-0.4 m below the main roots. If the autumn is early, rainy, then water-loading irrigation can be omitted or the depth of soaking may be reduced.
Be sure to cover the bottom of the trees with snow, creating the conditions for its conservation (so as not to blow the wind). Under the snow, the root system is better preserved, and in the rhizome - the kidneys of renewal.
Border crops must be insulated for the winter, mulched, protected from the drying wind in the winter (wrapping, swaddling). From burning sun rays in early spring, it is imperative to whiten the stamb and skeletal branches, and carry out other protective measures.
As they grow older, the young seedlings acclimatize and become hardened and will not react so negatively to weather disasters. Properly selected planting material will eventually become a beautiful garden or park recreation area, will delight with its exotic plants.