Row Covers

• Row covers are the simplest and cheapest form of greenhouse and cover a single row of plants. They can be plastic draped over seedlings or mature plants and anchored with earth at the edges, or the plastic can be draped over a simple, low framework. Hoops are commonly used as support. Special garden fabric is available just for row covers -- it lets in sunshine and rain but keeps out insects.
  
  

Cold Frames

• Cold frames are small boxes with slightly angled, clear, hinged tops that either sit on top of the ground or can be partially sunk into the ground to provide extra insulation for plants. They are easy to construct and can be made with many materials. Old concrete blocks make good walls for the box. Old windows can be used for the tops, which should face south. Acrylic panels or thick, clear plastic also work for the top. Cold frames are good for starting seedlings and overwintering plants.
  
  

Hoop Houses

• Hoop houses look like arched tunnels and can function like larger versions of row covers, but are more like traditional greenhouses. They are not difficult to assemble and can be made with a variety of materials. The most common construction method calls for a row of hoops made of inexpensive PVC piping covered with plastic clipped to the end hoops. They can be any length, and doors can be added.
  
  

Recycled Materials

• While special building materials are easily available, recycled materials, like salvaged lumber, can be used for all sorts of frameworks, as can building material cast-offs like electrical cables, rebar and piping. Old windows or picture frame glass can bring heat to plants. Greenhouse walls have even been made with plastic soda bottles and glass wine bottles. Buildings can be recycled as well. Think about adding windows and ventilation to an old shed or garage.
  
  

Traditional Greenhouses

• With a little bit of construction know-how, or just some really good instructions, a traditional greenhouse can be constructed from a kit or from new or salvaged materials. Modern greenhouses are usually clad in fiberglass, acrylic or plastic rather than glass because they trap heat better.