How to Protect Greenhouse Flowers from Freezing in Winter? A Detailed Guide to Practical Methods

After winter arrives in the north, there is a lot of wind and snow, temperatures are very low, and greenhouses remain closed for long periods, making freezing damage and wind damage likely. Therefore, greenhouse flowers require careful management to prevent the plants from dying. So,

Freezing Damage to Greenhouse Flowers

Different flowers should be managed separately according to their different cold resistance:

1. Add covers. At night, a small inner tunnel should be set up inside the greenhouse and covered with straw curtains. Adding straw mats or corn stalks around the greenhouse at night can raise the temperature by 1°C to 2°C. Adding a thin mat on top of the original straw mat can raise the greenhouse temperature by 2°C to 3°C. Covering the original straw mat with a layer of film not only blocks wind but also prevents rain and snow from wetting the straw mat, thereby reducing heat loss caused by water evaporation. For flowers planted in the ground, plastic film mulching can also be used, which can raise soil temperature by more than 1°C after covering.

2. Smoke around the greenhouse. Before a cold wave arrives, lighting fires around the greenhouse to produce smoke can prevent heat around the greenhouse from radiating into the upper air and reduce heat loss.

3. Clean the greenhouse film. Promptly cleaning dust, dirt and accumulated snow off the greenhouse film can increase light exposure and raise the greenhouse temperature.

4. Cover with plastic film or small arch tunnels. For greenhouse crops grown on high ridges, covering the high ridges with a layer of plastic film can generally raise soil temperature by 2°C to 3°C; for flat-bed cultivation, small arch tunnels can be set up to raise soil temperature.

5. Dig cold-proof trenches. Dig a trench on the south side outside the greenhouse and fill it with heat-insulating materials such as horse manure, weeds and straw, which can prevent soil heat from escaping outward and raise the soil temperature in the southern part of the greenhouse.

6. Double-film covering. Stretch another layer of film below the anti-drip film. Because there is air between the two layers of film, the temperature inside the greenhouse can be noticeably increased.

7. Water pool insulation. Dig a water storage pool every few meters in the center of the greenhouse, lay plastic film on the bottom of the pool, then fill it with clean water, and cover the top of the pool with a layer of transparent film (to prevent water in the pool from evaporating and increasing the air humidity inside the greenhouse). Because water has a high specific heat, it can absorb heat at noon (when temperatures are high) and release heat at night.

8. Remove mats at the proper time. When temperature conditions permit, remove covers as early as possible and put them back as late as possible to promote photosynthesis in the flowers. In deep winter, on clear days, the straw mats are generally removed in the morning when sunlight falls across the entire greenhouse surface, when the temperature inside the greenhouse is generally not lower than 18°C. On cloudy or overcast days, when light is weaker, the straw mats should also be removed at the proper time to let scattered light enter. On one hand, this can raise the temperature; on the other hand, because scattered light contains more blue-violet light, it is beneficial to photosynthesis. Never leave the straw mats in place for a long time, causing the greenhouse to become cold and dim and the temperature to drop sharply.

9. Apply more fertilizer. Add heat-generating materials such as horse manure and chopped grass into the greenhouse to raise soil temperature. The decomposition of organic fertilizer can release heat. Applying an appropriate amount of organic fertilizer and phosphorus-potassium fertilizer can not only improve soil aggregate structure, raise soil temperature and provide nutrients for the flowers, but also enhance the cold resistance of the flowers.

10. Hang reflective curtains. Hanging polyester aluminized film on the north side of the greenhouse can increase light inside the greenhouse and raise the greenhouse temperature by 2°C to 3°C.

11. Heating for warmth. In extremely cold weather, a stove or heating can be added inside the greenhouse, but when using stove fire for heating, be careful to prevent flowers from gas poisoning. A chimney should be installed to discharge the gas outside the greenhouse. Be careful not to burn firewood or grass inside the greenhouse to raise the temperature, because the smoke released when firewood and grass burn is extremely harmful to flowers.

12. Spread plant ash. Plant ash is gray-black and has a strong heat-absorbing capacity. After evenly spreading it on the greenhouse floor, it can generally raise soil temperature by 1°C to 2°C.

13. Spray antifreeze. Before the temperature drops, spraying the stems and leaves of the plants with a 400- to 700-fold solution of antifreeze can provide cold protection and freezing resistance.

Wind Damage to Greenhouse Flowers

In winter in northern regions, winds are strong, and the pressure lines of the plastic film on flower greenhouses cannot withstand strong winds, so the plastic film is blown open or damaged, and the flowers are destroyed as a result. The main reasons are: when the wind blows, the greenhouse film rubs against the frame; if the frame is not smooth, holes are easily worn through, and if they are not repaired in time, the holes become larger and larger; ventilation openings cannot be closed in time, and strong winds blow violently into the greenhouse, inflating the greenhouse film and causing film damage; if the greenhouse film is not stretched tightly and the film-pressing lines have elasticity or insufficient tension, large tears are easily caused; if anchor lines are buried too shallowly, the entire sheet of ground film is easily blown away by the wind; old, aged film with many tears is more prone to wind damage; poor quality film and frames cannot withstand the attack of fierce winds; improper management, failure to pay attention to weather changes, and failure to take protective measures in time.

The main measures to prevent wind damage are:

1. Set up windbreaks. At a distance of 1 to 2 m from the greenhouse, use corn stalks and sorghum stalks to make windbreaks. When building a greenhouse in an open area, there should be a windbreak forest belt around it.

2. Build greenhouses according to specifications. When building a greenhouse, strictly follow the requirements for greenhouse construction. The greenhouse walls and rear roof should be plastered and sealed tightly, the junction between the film and the rear roof should be tight, and a buffer room can be set up if conditions permit.

3. Reinforce the film-pressing lines. Use specialized film-pressing lines to press the film tightly. Change the conventional practice of 1 film-pressing line every 100 cm to 1 film-pressing line every 50 cm, and use 1 iron wire as a film-pressing line every 300 cm, tightened with a wire tightener.

4. Fix the ground film firmly. Use shared ground anchors. The method is: bury a brick with iron wire twisted around it every 2 m, at a depth of about 50 cm. Twist the end of the iron wire into a ring and leave it exposed on the surface. After burying, use 1 piece of No. 12 iron wire to string all the ground anchors together and twist it tight. Each film-pressing line can be twisted onto this shared iron wire.

5. Cover with a single whole sheet of film. Choosing the film is key. Use greenhouse film that is not old and has no holes, and use high-quality new film, such as a new-generation anti-fog polyethylene anti-drip greenhouse film. According to the greenhouse structure, choose a single sheet of film of the corresponding width, cover the ground with the single sheet as a whole, leave no gaps, and press the edges firmly and flat.

6. Cover with straw mats and strengthen management. After installing the film, manage it carefully. Tighten the film-pressing lines once every 3 to 5 days, and promptly patch any holes. To resolve the contradiction between ventilation for temperature regulation and wind blowing the film, place 1 straw mat every 3 to 5 m to press the film. When the wind rises in the evening, cover the straw mats one over another in the same direction as the wind, then cover the lower ends of the straw mats with more straw mats and press them firmly with stones. If the wind is very strong at night, pay attention to repairing damaged film in time.

7. Add a horizontal "belt." When using a covering method with 2 to 3 pieces of greenhouse film, a strong reinforcing strip must be added along each film edge at the seams as a "belt." The specific method is to clamp the film-pressing line or nylon rope used as the reinforcing strip inside the film, fuse and join the greenhouse film with an electric iron or soldering iron, and after installing the film, fix both ends of the rope, fixing it once every 5 to 10 m depending on the length of the greenhouse.

8. Master the film-covering method. The conventional film-covering method is to place the upper edge over the lower edge. Because this method leaves gaps at the joints, the wind encounters greater resistance, making the greenhouse film easy to blow open. If changed to placing the lower edge over the upper edge, the wind is less likely to blow the film open, and even if rainwater flows into the greenhouse, there is no major problem.

9. Improve the greenhouse structure. The spacing between the tie rods or binding rods of the arch greenhouse or greenhouse frame and the greenhouse film should be 10 to 15 cm. If the spacing is too small, first, it is easy to wear through the greenhouse film, and second, it has a supporting effect and makes it difficult to press the greenhouse film tightly. Therefore, the frame is required to be firm, and places in contact with the film should be smooth.

10. Persist with multi-layer covering. Adding double layers of straw mats, increasing grass blankets or cotton blankets, or using double-layer film, or adding small tunnels inside the greenhouse can all improve wind resistance.