A few weeks ago, we cross-published a post from Insteading that showed how to build a greenhouse by digging a (big) hole. I've been thinking about greenhouse plans myself over the last few months, and have been collecting up similar DIY plans. I've focused on one of our favorite sustainability topics, though: upcycling. Can you really build a useful greenhouse out of discarded materials, though? Well, we'll leave the judgments to you; I did find a number of interesting concepts for extending the Fall's growing season, or getting a jump on the Spring's.

1. The Plastic Bottle Greenhouse

Image credit: StripeyAnne via photopin cc

Developed as a lesson plan for British schoolkids, this detailed plan for a greenhouse from NEAD involves lots and lots of two-liter bottles… may need to raid the neighbor's recycling bins if you're not a big soda drinker (or, you know, ask them to collect them for you). You'll also need some easily-available framing lumber, gardening posts, and hardware for making sure it all sticks together…

2. The Old Windows Greenhouse

Image credit: hardworkinghippy via photopin cc

Got access to used windows of about the same size? Then you'll want to check out this plan at Instructables. Looks a bit more labor intensive than #1, but will also likely result in a more stable structure.

3. The Pallet Wood Greenhouse

The "5 Euro" label (or about $7 US dollars) strikes me as a little misleading, since it's hard to see how you get a genuine greenhouse out of this one without the horticultural-grade plastic (though I freely admit I may have missed something here). Regardless, I like the plan's use of pallet wood and wire fencing for much of the frame and roof: check out the video above to see how it all goes together.

4. The Storm Door Greenhouse

Good storm doors help keep heat inside a building while letting sunlight in, so they're a natural for a DIY greenhouse. This plan at Mother Earth News is the most complex of those presented here – it's even got a heating system – so if you're not particularly handy, might want to get some help…

5. The CD Spindle, Jewel Box, and/or Salad Container "Greenhouse"

OK, so these are exactly what you think of when you hear the word "greenhouse," but small plastic containers can work great for seed starting or indoor growing. Check out ideas for using a CD spindle case (detailed in the video above), CD jewel boxes, or plastic salad containers. (via WebEcoist)

Got your own version of the upcycled greenhouse? Do share…