It’s seed-starting season and spring is just around the corner. If you’re looking to start seeds indoors and realize that you don’t have enough windows space to sprout seeds indoors, or don’t want to raise your electrical bill by installing grow lights, building a greenhouse from recycled and salvaged items might be the solution you need.

1. The Window Frame Greenhouse

Probably the most popular examples of DIY greenhouses you’ll find on the Internet. This greenhouse by Angela Davis of My Rubber Boots uses old wooden windows that you can pick up at the local dump, architectural salvage store, yard sale, or even in your alley.The best time to salvage windows for this garden project is during construction and remodeling season where you live. Take Angela's awesome photo tour of her window greenhouse and garden.

Here's another window frame greenhouse, this one by Michael Taeuber, who created an Instructable to demonstrate how to build a greenhouse from old windows for his plants.

2. The Lean-to Greenhouse

Alex Campbell built this lean-to greenhouse, also using old windows, for his food growing operation.

He graciously documented his project so others could follow along and do the same. One of the benefits of building a lean-to greenhouse is that you can passively heat it during the cold with heat from the structure it is attached to.

3. The Poly Hoop House

Wolfie and the Sneak

Here's a simple greenhouse that you can build in one weekend. This was assembled by Wolfie and the Sneak blogger.

You’ll need a few pieces of lumber, a polyurethane sheet, and some “cattle panels” for support. Charlie Lybrand followed Adam Fyall’s directions for building a poly greenhouse. The temporary and portable nature of this example makes it a great option for gardeners who are renting or want to take advantage of the passive solar heating.

Check out the West Virginia University Extension Planning and Building a Greenhouse page for more ideas and directions.