The Best Greenhouse Plastics for a Longer Growing Season

With the right plastic, a greenhouse provides an optimal environment for extending the growing season, starting new plants, and protecting fragile specimens.

BobVila.com and its partners may earn a commission if you purchase a product through one of our links.

The Best Greenhouse Plastic

Photo: amazon.com

Abundant light is essential for healthy plant growth. While some greenhouse gardeners are fortunate enough to have greenhouse walls made from glass panels, the vast majority of greenhouses feature either rigid plastic panels or plastic sheeting. Compared to glass, plastic is inexpensive, lighter in weight, and, simply put, using plastic to build a greenhouse is easier. The greenhouse offers growers a chance to save money by raising seedlings to later transplant to the garden or provides a spot where tropical plants can survive cold seasons while still receiving ample light. The addition of self-watering planters, automatic drip systems, and automatic ventilation systems all increase a greenhouse’s ability to sustain plants.

Choosing the best greenhouse plastic involves considering the local climate and determining the type and size of greenhouse that is best for the plants growing inside it. Ahead, learn about the different types of plastic available for covering greenhouses and why they are well suited for many greenhouse-covering projects. Then, read on to discover some of the top-rated options on the market today.

  1. BEST OVERALL: SUNVIEW Greenhouse Clear Plastic Film Polyethylene
  2. BEST BANG FOR THE BUCK: Frost King P1025/6W Polyethylene Sheeting
  3. BEST UPGRADE: Arc Direct Clear Heavy Duty 14 Mil Poly Tarp Fiber
  4. BEST SUNBLOCK: YGS Perfect Sunblock Shade Cloth with Grommets
  5. BEST REINFORCED: Watershed Innovations Heavy Duty Clear Tarp
  6. BEST LARGE GREENHOUSE: Farm Plastic Supply 4 Year Clear Greenhouse Film
  7. ALSO CONSIDER: A&A Green Store Greenhouse Plastic Film Clear
The Best Greenhouse Plastic

Photo: amazon.com

What to Consider When Choosing the Best Greenhouse Plastic

The size of the greenhouse, the durability and price point of the materials, and the types of plants you plan to grow are all considerations when shopping for the best greenhouse plastic. The first thing new greenhouse gardeners will notice is the vast array of plastics on the market, from rigid panels that require a sturdy greenhouse frame to flexible rolls of plastic film to cover hoop or domed greenhouses.

In many communities, hoop greenhouses are a welcome addition to backyards and often don’t require a permit. However, to be on the safe side, check with local building authorities and any applicable homeowners association (HOA) before assembling one.

Material

Plastic’s ability to let in light while protecting plants from the elements makes it an optimal material for a greenhouse. Still, different types of plastic have their own benefits and considerations.

  • Polyethylene: The most common type of plastic for soft-side greenhouses, polyethylene, or “poly,” is used on agricultural, commercial, and home greenhouses. It’s affordable and comes in large rolls for attaching to the exterior frames of greenhouses. While polyethylene film doesn’t offer the same level of protection as rigid plastic panels, it’s easy to repair punctures and tears. Different brands may contain various plastic ingredients called “copolymers” that offer additional features (see below). Use polyethylene film on wood-frame and metal-frame greenhouses, but avoid PVC-frame greenhouses unless the PVC is first painted with a primer. PVC in its bare state can degrade polyethylene over time.
  • Polycarbonate: A rigid form of plastic, polycarbonate comes in flat or corrugated plastic panels for installation on the sides and tops of greenhouses. Polycarbonate is more expensive than polyethylene, but it offers a longer lifespan—up to 7 years or more—and is very durable. A bonus—polycarbonate is nearly as clear as glass, but because it’s not flexible, this plastic is not suitable for installation on domed greenhouses.
  • Polyvinyl carbonate: Another rigid and durable option, polyvinyl carbonate is sometimes used in greenhouse panels, but it’s even pricier than polycarbonate. It often comes in multiple layers, featuring a corrugated sheet encased between two flat sheets, and withstands high winds. Polyvinyl carbonate is usually slightly milky in color and available in a range of opaqueness options.

Size and Thickness

While rigid plastic panels range in thickness from a 1/16-inch single sheet up to a 1-inch multilayered sheet, polyethylene film is very thin. Most polyethylene film for covering greenhouses is an average of 6 mils thick. A mil is .001 of an inch, so a 6-mil polyethylene film is just .006 of an inch thick. Growers can often eke out 2 or 3 years of use from standard 6-mil plastic film, depending on the elements.

Polyethylene film thinner than 6 mils is often unable to withstand winds and is more prone to tearing. A handful of thicker films are also available, including 10 mils and 14 mils. These top-notch plastic films can last up to 5 years in some cases.

Single vs. Double Layer

Rigid plastic panels are not the only type of greenhouse plastic that comes in layers. Polyethylene film is also available in a double-layer option that features baffles or air pockets—think “bubble wrap.” It’s more costly than single-layer polyethylene film but offers added insulation and can sometimes last 5 years or longer.

The most significant benefit from any multilayer plastic is increased thermal value. It may make the difference between the temperature remaining above or dropping below freezing for greenhouse gardeners in colder climates. Don’t depend solely on greenhouse plastic to maintain a suitable temperature, however; supplemental heat may be required depending on how low the temperature dips.

Additional Features

Growing conditions vary widely from one area to another, so choosing the best greenhouse plastic requires considering whether any added protections will be necessary. Fortunately, greenhouse growers have a variety of additional options from which to choose.

  • Anti-drip: Also known as “condensate control,” anti-drip co-poly and rigid plastic panels are treated with an agent that reduces surface tension, causing droplets that form inside the greenhouse to run down the plastic rather than sitting on top of it or dripping to the plants below.
  • Reduced nighttime heat loss: To help retain warmth at night when temperatures drop, some types of plastic contain an infrared tint to reduce heat loss.
  • Reduced daytime heat gain: In warm, sunny regions, the temperature inside a greenhouse can become uncomfortably hot during the day. Plastic with reduced daytime heat gain contains pigments that block some of the heat. Growers will still likely need a way to ventilate the greenhouse, however.
  • UV protection: Greenhouse plastic with UV protection is designed to block ultraviolet rays, which may, in turn, reduce certain types of pest infestations, such as aphids and whiteflies. UV blockers don’t filter out beneficial light, only damaging UV rays.
  • Controlled diffusion: Similar in purpose to plastic treatments that reduce daytime heat gain, controlled diffusion softens the light that comes into the greenhouse, giving shade-loving plants plenty of light, but not direct scorching rays.
  • Light transmission: This is a percentage score commercial growers often look for when shopping for greenhouse plastic products. A light transmission score, called a PAR (photosynthetically active radiation) score, indicates the quality of light the plastic allows through to the plants. Plastic that blocks UV rays has a PAR score of around 88 to 91 percent, while plastic that features anti-drip sheeting has a score of about 82 to 87 percent. These percentages are typically referenced only by commercial and agricultural growers when ordering greenhouse plastic.
  • Photoselective: The color of light is just as vital to some plants as the quality of light. For example, plastic with a red hue may increase the size and health of roses, so specialty growers may seek out photoselective plastic, depending on the results they hope to achieve.
  • Reinforced film: Plastic film can be beefed up through reinforcement with a polyester mesh that gives the film added strength and reduces tears.

Installation

Depending on the type of greenhouse, installing polyethylene film is typically a simple matter of draping the plastic over the greenhouse frame and then attaching small strips of wood (furring strips) to hold it in place. This is a common way of installing plastic film on large or compact greenhouses. High-end film, such as double-layer film with baffles or insulating bubbles, may require a particular channel system that secures the film without penetrating the plastic.

Rigid plastic is often installed by cutting the panels to size and then inserting screws through them directly into the greenhouse frame. Reducing overly high humidity in a greenhouse (use a hygrometer to determine) can often be remedied by temporarily attaching the bottom of the plastic film to the greenhouse base but not nailing it in place with furring strips. When humidity rises in the greenhouse, simply roll up the sides of the plastic to offer ventilation.

Our Top Picks

To qualify as a top pick, greenhouse plastic should be durable, thick enough to resist tearing, and include the additional features an individual grower needs. While greenhouse requirements vary depending on the size of the growing operation and the type of plants being cultivated, any of these greenhouse plastic products would be well suited for covering most home greenhouses.

Best Overall

The Best Greenhouse Plastic Option: SUNVIEW Greenhouse Clear Plastic Film Polyethylene
Photo: amazon.com

Let the sun shine in! The SUNVIEW Greenhouse Clear Plastic Polyethylene Film is 6 mils thick, and with the inclusion of an infrared tint, it will let in a maximum amount of light while emphasizing the color red, which may increase the size and amount of flowers. The film will also block harmful UV rays to reduce the risk of scorched foliage on sensitive plants.

Users can attach this polyethylene film directly to wood or metal greenhouse structures, but it’s essential to prime PVC structures before covering them with this product to prevent plastic degradation. The film comes in a 12-by-25-foot piece and offers superior strength in a clear greenhouse film.

Best Bang For The Buck

The Best Greenhouse Plastic Option: Frost King P1025_6W Polyethylene Sheeting
Photo: amazon.com

Enjoy the benefits of extending the outdoor growing season without spending a lot of money on greenhouse plastic. The Frost King Polyethylene Sheeting is 6 mils thick and comes in a 10-by- 25-foot piece for covering greenhouse structures. Best of all, it’s available at an affordable price point. The sheeting features slight opaqueness but does not contain UV blockers, making it best suited for covering a greenhouse that’s protected from the hot afternoon sun.

While this sheeting doesn’t feature many bells and whistles, it should easily last 1 to 2 years. Like other polyethylene sheeting, make sure to prime a PVC frame before use.

Best Upgrade

The Best Greenhouse Plastic Option: Arc Direct Clear Heavy Duty 14 Mil Poly Tarp Fiber
Photo: amazon.com

The Clear Heavy Duty polyethylene greenhouse plastic from Arc Direct is a beefy 14 mils thick, thanks to embedded polyester mesh that makes this product more of a tarp than just plastic sheeting. The finished tarp size is just over 9 by 19 feet, and the edges are folded over and finished with reinforced rope for extra durability.

The tarp also features UV blockers and is rot- and acid-resistant. It comes with reinforced aluminum grommets spaced every 18 inches along the edges to stake the tarp to the ground for additional wind resistance. This thick greenhouse plastic lets in ample light and is extra thick, so it’s suitable for regions prone to high winds.

Best Sunblock

The Best Greenhouse Plastic Option: YGS Perfect Sunblock Shade Cloth with Grommets
Photo: amazon.com

For growing plants that need extra protection from direct sun rays, check out the YGS Perfect Sunblock Shade Cloth that’s designed to protect tender plants from harsh sunlight. This multipurpose cloth features 100 percent UV-stabilized polyethylene and can be installed over a standard hoop greenhouse frame. It features reinforced grommets along the edges for staking or tying down the cover and serves as an essential wind and sun break when used on a greenhouse. The shade provided by this polyethylene film makes it suitable for regions that experience a lot of hot sun. It’s available in a lightweight yet durable 10-by-20-foot piece.

Best Reinforced

The Best Greenhouse Plastic Option: Watershed Innovations Heavy Duty Clear Tarp
Photo: amazon.com

From the HydraTarp family of Heavy Duty Clear Tarps by Watershed Innovations comes this 10-mil polyethylene clear tarp that’s well suited for covering a greenhouse. The plastic is reinforced with a polyester cross-weave mesh that gives the clear plastic added strength and durability. In addition, the tarp features UV blockers and reinforced grommets every 36 inches along its rope-hem edges. It measures 12 by 24 feet and is both waterproof and rot resistant. Especially due to the double-reinforced corners, this greenhouse tarp offers strong protection against the elements, making it ideal for regions subject to high winds or storms.

Best Large Greenhouse

The Best Greenhouse Plastic Option: Farm Plastic Supply 4 Year Clear Greenhouse Film
Photo: amazon.com

Cover a sizable high tunnel or hoop house with the Farm Plastic Supply Clear Greenhouse Film that measures 24 by 50 feet (other sizes may be available). At 6 mils thick, this simple polyethylene film is well suited as a greenhouse cover, and it includes UV blockers to protect plants from scorching sun rays. The film is suitable for use on a wood- or metal-framed greenhouse structure. It can be installed in a double layer on a smaller structure if desired to increase thickness and wind protection.

Also Consider

The Best Greenhouse Plastic Option: A&A Green Store Greenhouse Plastic Film Clear
Photo: amazon.com

Protect new seedlings from the elements with the A&A Green Store Greenhouse Plastic Film that comes in an 8-by-25-foot piece (other sizes may be available). The film is 6 mils thick and designed to resist tears from high winds and storms. It includes UV blockers but still offers a maximum amount of light transmission, making this film well suited for placement in a spot that provides at least some protection from the hot afternoon sun. This polyethylene sheeting also helps retain heat after the sun goes down, which may extend a gardener’s growing season. Install on a wood- or metal-framed greenhouse for the best results.

FAQs About Greenhouse Plastic

Having a greenhouse opens a world of growing possibilities that aren’t available inside a typical home with limited windows and space to start seeds and care for plants. Growers wanting to produce healthy vegetables or grow flowers in a greenhouse will likely have some questions about the types of greenhouse plastic available.

Q. Does greenhouse plastic block UV rays?

If the plastic has been treated with UV blockers, then it will reduce harmful UV rays.

Q. What is the difference between clear vs. white greenhouse plastic?

Clear plastic lets in more direct sunlight than white greenhouse plastic. Most plastics are somewhere between crystal clear and white, with many featuring just a touch of opaqueness.

Q. Can I use regular plastic for the greenhouse?

The best plastic for greenhouses is “greenhouse plastic” or “agricultural plastic.” Regular plastic sheeting, known as “utility plastic,” may not hold up to the elements as well, but it will still offer a measure of protection.

Q. How do you install greenhouse plastic?

For the easiest installation, drape plastic film over the greenhouse frame and attach it with furring strips. Rigid plastic panels are typically screwed directly into the greenhouse frame.

Q. How do you clean greenhouse plastic?

If the plastic becomes dusty or dirty, a light misting with a garden hose will usually rinse away dirt. To remove heavy accumulations, add a few drops of dish soap to warm water, wipe down the plastic, and thoroughly rinse. Avoid using a pressure washer that could tear plastic film.

Q. How long do polycarbonate greenhouses last?

Among the longest lasting of all greenhouse plastics, rigid polycarbonate plastic panels can last up to 10 years before requiring replacement.