After 15 years, this greenhouse of redwood and polycarbonate, has finally come out from under tarp and mouse droppings. It was purchased for my project at Socrates Sculpture Park in Long Island City, Queens, in 2001, assembled amidst the acrid haze of September 11, and the structure became a refuge during a very dark time. The company, Gardenhouse, generously donated their profit by giving the structure to my project at their cost.
Our site, formerly Rex's dog pen, was excavated last fall and filled with Class 5 gravel (a mixture of 1 inch or less rock, sand and some clay), hand compacted by me this spring, and laid with the cheapest concrete pavers from a preferred regional box store. Redwood is great for this kind of structure because it really doesn't warp and is one of the best rot-resistant woods. The polycarbonate held up well, but I hosed down the panels last fall and the hard water left spots inside the double walls. Oh well, still have a greenhouse!
I am renovating a portion of our front porch deck so that I could use the old, long cedar planks as framing for our raised herb bed. After ensuring the rusty screws and nails were out, I ripped the boards on the table saw to cut out the rotted sides. The heart of these boards are perfect, so if you are looking for free raised bed material I would look for a deck carpenter in your area. Our boards haven't been treated in at least sixteen years, if ever, and each had a nice coating of algae and lichen. Still, I placed the up-side out and the underside toward the planting. You could do the same if you are concerned or unsure about the treated nature of free, old deck boards.
After building the first raised bed I rather liked the structure over the hastily made front yard vegetable beds of last year. I had potatoes to plant and thought a raised bed would be easiest for "soiling up" mid season. I tilled, built the two side walls out of 14 foot old cedar deck boards, added humus from the base of a giant old oak tree that spits out a fine, peaty substance from a portal 5 feet up its trunk, then added the rotting straw that covered the garlic beds, and finally several cubic feet of compost. I left the 40-inch end boards off so I could run the tiller through to mix these ingredients in.
I dug a trench and planted the potatoes at about 12 inch spacing, covered the potatoes, then dug the center trench and so on. In a raised bed with rich soil I am anticipating that I can tighten my spacing. Don't take my word for it, however, see Rodale's 7 Ways to Grow Potatoes.
The greenhouse, nearly completed (still rocks for the back and side, one vent operator to install and some window cleaning). We moved our New Mexican Opuntia and Agave inside the greenhouse, mostly to avoid the cold rains, but also to get them more sun than the house could provide. The front of the greenhouse will be tilled and seeded for grass, then stepping stones or maybe brick walkway from the garage pad to the door.
Inside the greenhouse, on a quick-built table made of cedar taken off the house last fall, are starter trays and cold-stratified milkweed seeds of seven varieties. I am generally two weeks behind on most projects, so these got started a little late, but milkweed enjoys warm soil sprouting (you'll notice even well-established plants are some of the latest to come up). The milkweed seedlings are sprouting and now share the table with summer vegetable seedlings and strong-looking starts purchased last week at one of our area's better unique and heirloom variety vegetable nurseries -Shady Acres.
If you are thinking of a free-standing greenhouse like this, I'd like to offer some considerations. Make sure you have a solid base to build on that is level as these greenhouses won't piece together well if they are bent out of form by off-level pads. Make sure you place it in a sunny location! Don't laugh, if you build in fall or early spring it could be quite sunny, but not from May through October. Do consider wind and overhanging branches. Gardenhouse says it can withstand a wind load of 85 mph. Why chance it? Make sure to anchor it in some fashion, put it in an area that provides a windbreak yet doesn't allow a large limb to come down on it (note that home insurance usually doesn't cover structures like these). Finally, if you have lots of paper wasps, they will love to explore your new greenhouse as a fine place for their nests of stinging motherf$#ers. I was stung four times last year, mostly because I put my hands near a nest I could not see. Paper wasps are very observant and will watch you as you get close. They will leave you be if you do not get too close, but if you do, in a flash one or more will drop on you and leave its painful stinger. In short, you may have to spray a long term pesticide on the rafters, as difficult as that decision is. Wear a mask, cover your skin and eyes, because it's hard to avoid getting doused when spraying up into a pitched roof. Don't forget places like under a table. The long term stuff should last all season, meanwhile you can use clear sealant to close up gaps that allow creatures in, and with some luck, the next year you will not have to spray.