Light deprivation is a valuable technique used in greenhouse growing to control plant productivity and extend growing seasons by precisely managing exposure to light. To effectively establish this level of control, growers rely on light-deprivation tarps and covers.
Light-dep covers are vital in blocking light during specific periods, mimicking natural cycles of light and darkness, and promoting optimal plant growth. However, not all light-deprivation tarps and covers are the same. When choosing a greenhouse cover, it’s essential to consider the unique features of each product and how they align with your light-deprivation strategies.
Black and White Panda Film
One of the first considerations when selecting a cover is the color. The most common type of light-deprivation cover is a two-toned black and white film, commonly called panda film. The white side is highly reflective, which diverts both light and radiant heat, keeping the greenhouse cool and reducing temperature fluctuations. The black side blocks out sunlight, enabling precise control over growing conditions.
Some users prefer to use panda film with the white side facing up year-round, while others switch between the two sides depending on the season. When the white side faces out, it reflects radiant heat. It creates a blackout effect in the greenhouse, keeping the interior dark and temperatures relatively cool. This effect is beneficial when simulating fall or winter conditions for an off-season harvest.
Conversely, sunlight transmission is blocked when panda film is deployed with the black side facing out. At the same time, interior light is reflected in the growing space. The white interior also helps retain the heat of the growing area, which is valuable in cooler climates that use artificial lighting and supplemental heat to mimic spring or summer conditions.
Many horticulturists have found that low-quality panda liners only partially block light. However, high-quality materials are usually thicker, more opaque, and less susceptible to developing pinholes and tears, which can wreak havoc on your light control efforts.
All-Black Covers
Alternatively, some growers prefer all-black covers for their light-deprivation needs. These covers are designed to completely block out light without any reflective properties. While all-black covers may offer a more intense blackout effect than thin or low-quality panda liners, they do not provide the reflective benefits of a white side.
The choice between black and white panda film and all-black covers ultimately depends on the grower’s budget, specific needs, and operational preferences. Some growers prioritize the reflective properties of the white side, while others prioritize a complete blackout effect.
UV Warranties
One significant consideration when choosing a light-deprivation cover is its resistance to UV radiation. Exposure to UV rays can lead to the degradation and deterioration of the cover over time, significantly reducing its effectiveness and lifespan. Since light-dep covers are designed for full exposure to sunlight, selecting a material that offers some level of tolerance to UV radiation is essential.
While polyethylene is generally not resistant to UV radiation, black-colored polyethylene is an exception due to the addition of carbon black during manufacturing, which acts as a UV stabilizer. Carbon black absorbs or screens out electromagnetic radiation in the UV-A and UV-B ranges, preventing UV degradation. Therefore, it is advisable to choose high-quality panda covers that also include UV stabilizers on the white side.
Low-density polyethylene (LDPE), on the other hand, is highly susceptible to UV damage. Research has shown that it begins to degrade after just five days of exposure to UV-B radiation. As a result, light-deprivation covers made with LDPE alone typically last only for a single growing season.
Choosing a cover with a UV warranty whenever possible is recommended to ensure long-lasting performance and maximize return on investment. A UV warranty guarantees the light-dep cover will maintain its UV resistance for a specified period, providing growers with peace of mind. When comparing different covers, it is crucial to consider the length and coverage of the UV warranty and its effect on the bottom line to make an informed decision.
Durability and Reinforcement
Durability is another primary consideration when choosing a light-deprivation cover. The cover must withstand the rigors of daily deployment, including pulling and stretching, without tearing or deteriorating. Reinforcement plays a crucial role in enhancing the durability of the cover.
There are various reinforcement methods, such as using more robust materials or incorporating additional layers. Scrim reinforcement is a common approach, where a woven scrim is embedded within the cover’s layers. This reinforcement helps distribute stress and prevent tearing, ensuring the cover’s longevity and reliability. Even in the event of a tear, a reinforcing layer prevents it from spreading, making repairs easier without compromising the overall durability of the cover.
When comparing different light-deprivation covers, it is essential to consider the thickness, material quality, and reinforcement methods used. Generally, a thicker cover made from high-quality materials and featuring effective reinforcement will offer significantly better durability and a longer lifespan. However, it is important to balance these factors with the overall weight of the cover, as a heavier cover can significantly impact the labor involved in manual deployment.
BTL Liners’ ArmorCover
One brand that stands out in light-deprivation covers is BTL’s ArmorCover line of products. Made of reinforced polyethylene (RPE), these covers are engineered with two layers of polyethylene coatings co-extruded with a central reinforcing layer of woven HDPE or polyester string scrim. With products ranging in thickness from 9 to 16 mils, these high-quality light-dep covers offer an exceptional balance of durability, UV resistance, and light-blocking capabilities, ensuring long-lasting performance and protection.
