General information about frost damage effect on the plants
Frost damage on plants can occur if the temperatures are very cold, usually when dropping below 0°C. Steam bending occurs when the temperature drops as plants struggle to protect themselves. Large leaves can become stiff and break off. Plants may also become water-soaked and the buds may turn black and die. This will create a situation that will last until temperatures rise again. When you see the frost has attached to your plants, quickly remove the damaged leaves and buds. Then use different plants’ protection against frost which will be explained in this text below.
The optimal temperature for the majority of higher plants (mesophile), ranges from 10 to 30°C. This means that when the temperature starts dropping below 10°C, these plants start experiencing a different level of stress. And if the temperatures drop below 0°C, and the frost hits the plants, they are two levels of damage:
- Extracellular level (protein denaturation, osmotic stress, and oxidative stress)
- Intracellular level (direct danger to the membrane of the plant cell)
Typically, those ice crystals you sometimes see when the frost hit on the plant is damaging in these ways. On the outside part of the cell, the water balance change in the way that dehydration is caused to the plant. On another side, if the frost hits the inside part of the cell, the plant will suffer categorical damage. These damages will be irreversible.
The tolerance of the plant against frost is usually content with the origin of the plants. So, plants that originate from the tropical and subtropical regions will have a very low tolerance against frost. Usually, any temperature above 0°C, will cause and unrepairable damage to these plants up to the complete death of the plant. On the other hand, plants that originated from cold regions will have a stronger mechanism of protection against frost.
Acclimation against frost stress
Acclimation of plants to freezing stress is also required for the possible survival of overwintering plant species in northern regions. This approach will be useful in continental climate too and with the global warming trends, soon we will see the need for worldwide use of acclimation techniques.
There are several techniques used to make the plants harden against frost. For instance:
- Using frost cloth
- Pre-incubation in cold
- Treatment with Abscisic acid (ABA), a plant hormone.
Using these methods will harden your plants and will make them experience the frost stress will far less damage.
What is frost cloth (different types of frost cloth, their material, their role)
Frost cloth is a light fabric raw cover that is best suited to plants that require protection against strong frost. Plant species like conifers, flowering plants, herbaceous shrubs, trees, vines, and sodalites are best protected with frost cloth. Typically, frost cloth is made of:
- polypropylene or
Due to its lightweight, this material is applied directly to the plants. Because of its good ventilation, water and lights cannot go through it and the plants are not damaged. In general, frost cloth is designed to be removed when soil temperatures rise above freezing.
Non-woven polypropylene fabric:
This is a material from polypropylene fabric, with a wide range of usage. With more focus on vegetable growing, gardening, and fruit growing. Mainly used to cover plants and maintaining a normal temperature on the greenhouse condition. In another hand, this fabric can be in mulching soil during the hard winter times for forest plants.
This unique fabric can also protect your plants from snow, prevent root disease, and prevent harmful insects to attach your plants.
Knitted polyethylene is a material used to protect crops and plants from frost. It keeps crops frost-free by creating an insulating, frost-proof layer around the plants’ roots. These materials are in different colors. These knitted polyethylene bags are easy to put on the plants and keep them covered from freezing overnight. They are 100 percent biodegradable and can be used for multiple crops. These materials are knitted from thin strips of strong – but very light transparent UV stabilized polyethylene thread.
Why are they so useful?
A polyethylene sheet protects from any kind of cold during the year. The material is light enough to use as a drop cloth to protect plants from pests. A single sheet can protect up to 3 square feet of soil or 4 square feet of plants. They can also be used for greenhouse growing and greenhouse gardening. The material can be sprayed on or knitted together with small holes in the sheet for air circulation. They can be used as floating rafts in ponds to help control aquatic pest populations. “Polyethylene is a very durable, stable material that is resistant to oxygen, water, and the degradation process that leads to degradation”.
Where to use a frost cloth？
If you want to use frost cloth in horticulture, you should first check the requirement for each variety of plant, because some plants can only handle very specific temperatures. A frost cloth made to cover a whole plant might be too big for it, whereas a frost cloth which is meant for smaller plants might be too small. In the table below we can see different usage of this material for several plant categories.
Commercial Growers： Rosemary, Summer Squash, Sweet Potatoes, Tomato, Lettuce, etc.
Flower Growers： Coneflowers, Dianthus, Zinnias, Marigolds, etc
Nurseries： ornamental trees, shrubs, perennial vegetables, bulb crops, etc.
The most popular types of frost cloth
The most popular types of frost cloth in plants are those that are mostly or completely transparent when used at moderate temperatures, which allow the plants to show how well they are doing or detect whether a particular plant has a problem. If you are using an opaque frost cloth, the light that passes through it will likely be absorbed by the frost rather than reflected. This light is of a limited spectrum that is usually invisible to plants.
Other things you can do to protect your plants from frost?
Some plants do better than others in very cold temperatures. A cool climate or tropical plant will struggle to survive cold weather. It’s important to remove frost cloth as soon as it begins to thaw so as not to damage a plant. Do not forget to remove the protective plastic sheet as well, which is usually relatively easily pulled off when the frost has completely melted. Some plants do just fine in cold weather, such as azaleas and rhododendrons. However, many plants will need special treatment to make them more tolerant of cold. This could involve a protection layer, a liquid feed, or additional water in very cold weather. It might even mean they need a period of cold treatment, such as putting them in a bulb vase to reduce the temperature. So, if you know that your plants will be outside in winter, you should try to make them a little bit more frost-tolerant.
When building the structure of the frost cloth the fabric must no have contact with the plants. This is because the frost will be transferred to the plants and we will miss the aim of using these materials. To facilitate this process installation accessories are used and, in the table, below you can see some of them and their usage.
- Wire and bungee cords
2. Metal stable
3. Plastic hooks and pins