If you have decided to build a greenhouse on your property, there are a number of simple designs you could use. Picking a simple design, that is reliably easy to build, would be the best route to take if want to have a greenhouse built in as little time as possible. Two designs to consider are the lean-to and hoop style greenhouses.
The hoop greenhouse is very simple to construct and can be built in less than an hour, if you have all the materials on hand. It is simply a row of plastic hoops, cut into semi-circles, with a transparent plastic tarp draped over the frame. Its constructions is simple. hammer two rows of metal rods or narrow wooden stakes into the ground, parallel with each. Fit the ends of a series of plastic hoops cut in half, over the rods. You can use narrow plastic tubes as an alternative. Just bend them and place the ends over the rods you hammered into the ground. Place a transparent plastic tarp over the frame, covering the two ends and sides right to he ground. Leave a little extra on the ground. rocks or wooden beams can be used to hold the plastic tarp down. A door can be made by cutting the tarp hanging over either end of the hoop frame.
The lean-to greenhouse is a great option if your backyard is to small for a hoop greenhouse and you need something with more head space. This structure is simply a greenhouse cut in half at the ridge of the roof. It is attached to the side of a building for support. It can be placed on a patio or sidewalk.
Which ever greenhouse you choose to build depends on what you want to use it for and its location. Both these greenhouses are simple to build and work great for the purpose they were designed for.