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Greenhouse plastic is a film or panel product designed to be used in the construction of greenhouses, cloches, and similar garden installations. It has a number of features specifically implemented to protect plants, differentiating it from other plastic sheeting products like construction plastic. Gardening and home supply stores often carry greenhouse plastic and it can also be custom ordered from a manufacturer or supplier, an option for people who need unusual sizes.
Polyethylene films designed to be stretched over frames are one option. Their thickness can vary, and this determines the average life as well as insulating properties available. Thicker plastics tend to last longer, especially if they are installed with care, and they also provide more insulation. They can be doubled up with an air cushion between the layers for greenhouses in very cold climates where added insulation is necessary.
Another option is polycarbonate panels, which are rigid rather than coming in the form of flexible sheeting. They also come in several sizes and thicknesses suited to different projects. Thick paneling offers more insulation and weather protection, and also tends to be more expensive. It can be attached to wood, metal, or plastic frames, just like films. In both cases, it is important to install the plastic in temperate weather, with products designed to work with plastic, to avoid a too-loose or tight installation.
One feature of greenhouse plastic is ultraviolet protection, which limits damage to the plants inside. The plastic is also designed to reflect heat back at night so gardeners don’t need to use as much heat to keep plants safe in the cold winter months. In addition, condensation is encouraged to form on the plastic and drip along the sides of the greenhouse, rather than falling onto the plants and exposing them to injury. Greenhouse plastic also diffuses light within a greenhouse to provide plants with bright, even light, which can be ideal for cultivation.
Some considerations when selecting greenhouse plastic can include climate and needs. In windy, harsh climates the plastic should be tougher so it will be able to resist the weather effectively. It also needs to be carefully installed so it doesn’t tear or rip off during inclement weather. More mild regions may be suitable for lightweight plastics designed primarily to offer some protection rather than to create a hothouse with a radically different indoor temperature. Plastics tend to be less expensive than glass, and can be good for temporary structures or starter greenhouses while gardeners get established.