Before the soil freezes. The closer the irrigation time is to freezing, the better the effect will be. Water the soil once before freezing. After the soil contains more water, the ground temperature will not drop too low or too fast in severe winter, but will rise slowly in spring. Generally, green water is watered in early spring. Due to the large temperature difference between day and night in early spring, timely watering green water can reduce the temperature difference between day and night on the surface and avoid the damage of spring cold to plant roots.

(2) Burying cold-proof soil

Full burying: suitable for small seedlings with elastic stems. Before the soil freezes. Press the seedlings forward and cover the two sides with soil, with the thickness of 10 ~ 15 cm. After defoliation, such as deciduous seedlings, the soil should be cultivated. For Sabina vulgaris and Buxus microphylla seedlings of 1 year, they can be covered with cattail and then compacted with soil.

Soil cultivation: suitable for seedlings with large specifications or hard and brittle stems, such as Ligustrum lucidum, pomegranate, cedar and transplanted seedlings in the same year. After filling with frozen water, cultivate the soil around the seedlings with a height of 30 ~ 50 cm.

The burial time should not be too early, but should start before the soil freezes. Seedlings buried prematurely are prone to decay. The time of soil withdrawal in the following spring is also very important. Early withdrawal is easy to suffer from physiological drought, and late withdrawal is easy to hurt seedlings or even rot. When the seedlings are cultivated or before the seedlings begin to grow, the plastic film should be taken back twice.

(3) building windbreaks

Used for cold protection of evergreen tree seedlings, such as cedar, cypress, Euonymus japonicus, Ligustrum lucidum, etc. In autumn and winter, straw or plastic cloth is usually used. Now, polypropylene striped woven cloth is used to protect plants from wind and cold. Windbreak walls should be set up on the north and west sides of the nursery area. The effective cold protection distance of the wind barrier is 10 times of the height of the wind barrier.

(4) scientific fertilization

Apply less nitrogen fertilizer in autumn to control the growth of seedlings, promote their growth and enhance their cold resistance.

(5) packaging the dried seedlings

For large seedlings, it is usually done before winter, and the trunk of the seedlings is wrapped or bandaged with straw rope or sacks, and the height can be about 1.5 ~ 2 meters.

(6) Paint the dried seedlings white.

For big seedlings, it is usually carried out in autumn. The mixture of limewater and salt or sulfur is coated on the trunk of seedlings, and the sunlight is reflected by white, which reduces the absorption of solar radiation heat by the trunk of seedlings, thus reducing the temperature difference between day and night and preventing the bark from freezing. Focus on the southwest of Miaogan. In addition, this method also has a certain effect on pest control.

Before freezing. Apply slaked lime on the seedlings to form a protective film. This method is often used for some seedlings with poor cold resistance and fear of sunburn, such as Toona sinensis, persimmon, acacia, Platanus acerifolia and aesculus. The concentration of the coating agent should not be too thick, and an appropriate amount of adhesive should be added to prevent the coating agent from falling off. The formula of whitening agent: 5 kg lime, 0.5 kg sulfur and 20 kg water.

(7) coverage

Before frost, cover the ground with hay, straw mats, horse manure, leaves, sawdust, straw, etc. It can also be covered with plastic film and other materials to level the seedbed, and the surrounding is compacted with soil.

(8) fumigation

Generally, it is carried out on a clear night to ignite the haystack and reduce the heat loss of the soil by smoke. When the temperature is too low, the effect of using this method is not obvious, and it causes certain pollution to the environment, so this cold-proof measure should be avoided as far as possible near the urban area.

(9) Heel cold protection

It is mostly used for some tree species with poor cold resistance at seedling stage, such as Platanus acerifolia, Lagerstroemia indica, Cercis chinensis, Buxus macrophylla, Cedar seedlings and so on. Combined with the transplantation in the next spring, before freezing, the seedlings were dug and graded into ditches and pits for rooting.

(10) cold penetration inhibitor.

This method can be used for evergreen trees with poor cold resistance, such as cedar and cypress, and deciduous trees that are easy to branch in winter, such as Lagerstroemia indica, French phoenix tree and Ligustrum lucidum. At the end of winter and the beginning of spring, spraying 200 times diluted raw powder (liquid) with a sprayer can make the high-fat film adhere to the surface of branches and leaves for about 10 days, which can be sprayed continuously for two or three times. It should be repainted after rain and snow.

(1 1) intercropping for cold protection

Intercropping small seedlings that are not cold-resistant among large evergreen trees with large plants and large row spacing to form a windbreak fence. Such as Sabina vulgaris, Platycladus orientalis, Cedar and Juniper, planting hedges such as Buxus macrophylla, Buxus microphylla and Ligustrum lucidum in the middle of large row spacing can greatly improve its overwintering preservation rate.