Plastic film is the most cost-effective material for greenhouses. In addition to affordability, it is also durable. There is no “one size fits all” when choosing a greenhouse plastic. There are several factors to consider when trying to select the correct greenhouse plastic for any operation.
How Thick Should The Plastic Be?
Plastic sheeting is measured in “mils.” A mil is equal to one-thousandth of an inch (0.001 inches). A grocery store bag is .5 mil. Greenhouse plastic typically measures between 5 and 8 mils. Some products are available with a thin twine built in the film for reinforcement and structure, and some have UV inhibitors.
Consider the geographic location of the greenhouse when selecting the correct thicknesses (mil) of film. The wind is a significant factor in plastic damage, and you don’t want to replace your plastic film multiple times a year. A thicker mil product, 6-8mil, with double the tensile strength, increases the protection of the film and crops during mild wind gusts.
Careful evaluation of the environment and the risks involved will help you select the right mil of film.
What Kind Of Plastic Should Be Used?
Several different types of plastic are used, and they all have various applications for the best results. Below are a few of the popular films and best application for them:
Panda Plastic Film
The greenhouse panda film is used in growing areas. This is a waterproof poly film that is black on one side and white on the other. Black and white plastic sheeting is used for crop control management. The white side is highly reflective and used to direct light away. The black side is entirely opaque and absorbs light, keeping heat and light away. It is also used for waterproofing and temperature control.
- A brilliant white layer ensures maximum light reflectivity to aid in vegetable crop production.
- Provides maximum control when used as a blackout curtain for your crops.
- Greenhouse blackout film reflects heat and cools better than shade cloth.
- This black and white poly film is explicitly designed to withstand the wear and tear of either foot traffic or retractable curtain systems so that crop management control is not reduced in higher-stress applications.
- High strength at folds of the Panda film means higher resistance to punctures and tears. In any greenhouse plastic film, weaknesses can occur where the polymer strands are bent at a fold. Increased fold strength minimizes performance issues in these critical areas.
Clear Plastic Film
The pros of using clear greenhouse plastic is that it delivers direct light into the structure, which heats the soil providing optimal temperature for seed germination. Only use clear plastic if you use a greenhouse for germinating seeds and growing starters for transplanting outdoors. Direct light encourages germinating seeds to sprout and develop into strong seedlings ready for transplanting outdoors.
Frosted/Opaque Plastic Film
The main disadvantage of using clear vs. opaque or frosted greenhouse plastic is that direct light creates hot spots while leaves other plants in the shade. It also produces excess heat that is trapped in the greenhouse. Unlike clear sheeting, opaque plastic scatters light waves and provides even light for optimal plant growth.
Diffuse light reaches all areas of the greenhouse and produces the most efficient photosynthesis. Also, because it reaches plants at different angles, they are not leggy as they don’t try to grow towards available light. It is essential if you are growing tall vegetables or growing vertically on benches.
Black Plastic Film
A greenhouse that uses a total black sheeting is for light deprivation. Light deprivation is a breakthrough greenhouse concept that is now very commonly used to stimulate flowering. A black plastic mulch conserves soil moisture by preventing it from evaporating. Only the exposed soil in the holes where the plants are growing lose water to evaporation. This means that more moisture is available in the surrounding soil for plant roots and can spend less time watering the growing crops.