Friday, March 20, 2009

Little Green Houses For You and Me

Why it would possess me to build a greenhouse in the spring I have no idea. There is little to nothing you can do with a greenhouse in the late spring to late summer. And in Virginia, there's not much you can do with one in early fall either.

But come late October, it's a wonderful place to move my plants into, and try to stretch out those last few weeks of fresh tomatos or green peppers. And come February, it's perfect for watching new seedlings come up, or stashing those plants I bought on a whim that are months away from being able to survive outdoors.

After years of dreaming of having my own greenhouse, we finally decided to make an economy version. Of course, the one in my vision was a proper English greenhouse complete with metal Victorian finials on the peaks. Preferably with my own castle in the background.

Since that's not likely to happen anytime soon, I researched hoop greenhouses on the net.

Using an existing raised bed, we took 10' lengths of 1" PVC, connected 2 lengths and bent it so that it spanned the 12' garden bed, attaching each end with U-shaped clamps.

The idea was that plastic could be laid over the hoops, and anchored on either end with soil. The door would be double-layer plastic on one end.

This was one of many plans I found on the net - there are other variations, including one with the plastic anchored on the interior with 40 lb bags of potting soil, which are then cut open and used directly for planting. Liked that one too.

This idea did not work for us, for several reasons. The construction works very efficiently at trapping heat - too efficiently. By the time we had finished stretching the plastic, the temperature inside was over 120 degrees. And there was no way to vent it. Hmmm.

After trying to work out a venting system (without much luck), we discovered this sort of greenhouse is not suitable when you live just beneath a ridge that funnels the wind down across your yard. The entire greenhouse was flat within days, and the plastic shredded. Back to the drawing board.

Our next plan was to mix the "hoop" idea with a solid wooden half frame, adding a recycled joulousie-window on one end and a screen door on the other end for venting.

Better. But the hoops continued to shift and bend whenever there was a slight breeze, even though they now had a center ridgeline pole to help them hold their shape. Plus there was no way to hang plants. So, we decided to re-design yet again (at this point it was a matter of stubbornness more than anything else).

The last design involved separate plastic panels with wood frames (if one panel has a cut or failure, only that panel has to be replaced), and additional hanging bars on the inside. Also, a wooden frame is added to the ceiling, plus the bottom half is enclosed with wood.

And finally, it's done. The little vents on each side of the door were recycled metal heating vents that open and close as needed. The screen door has a plastic sheath that is used in the winter (although we've since decided to purchase a second screen door, and just exchange out the door versus putting plastic on and off -it's easier on the door frame). The dark green base helps collect heat and warm the interior in the winter (and it does a pretty darn good job in July too), plus it's my favorite color.

The plastic I used is from:
and it is the most wonderful product I have ever used - it does not split, yellow, tear or breakdown under the hot Virginia sun. Save yourself major headaches and do not attempt to use the roll plastic commonly found at the local home improvement store - even the heaviest mil they sell is not strong enough for greenhouse use. We've used this North Dakota plastic for 2 years now, without any problems at all. Ask for Bob -he's a great guy.

Because we took the long way around, the greenhouse cost us almost $1000. However, I console myself knowing a comparable kit for a 12'x12' greenhouse is approximately $3800.00.

If we had gone directly to the final design (i.e. had a clue about what we were doing), cost would have been approximately $500 ($100 is for the plastic), and would include wood, hardware, the door and window (found at a Habitat For Humanity store for $15), and Thompson's Sealer for the wood.

What if there's no $$$ for greenhouses? Do you have an existing structure in the yard you can re-use?

This is the leftover frame from my daughter's swing set. At one point we covered it with a large sheet of plastic and used it to set bedding plants in. With a small amount of wood, it could be enlarged, squared off to hold a door, and made into a 10' x5' mini greenhouse. Currently ours has trellis stretched over it for morning glories or gourds to grow on. The base area has topsoil and organic material added for peas and beans. Come July, the morning glories and gourds will stretch out the growing time for peas.

Another idea - for that old shed - is to remove the roof, stabilize the interior, and cover the top with the fiberglass panels available at Lowe's - 12' long by 2' wide, for approximately $28 per section. To increase the amount of light, use a Sawz-all and cut one side of the shed down a couple feet, then install your roof panels - and make sure the slope faces the direction of the strongest amount of daily sunlight. Use inexpensive caulking to seal the shed. Something this simple will provide a warm enough sheltered spot to start seedlings or protect a few plants in the fall.

For more ideas, check out Building Your Own Greenhouse by Mark Freeman (over on the bookshelf, and yes, it's available used.)

Of course you could always just put in a simple cold-frame, but that's another post.

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