Bob's A-Frame Greenhouse — You can build a greenhouse like this, too!

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- Bob's Project Ideas -

Raised Growing Beds

Inside my large rebar greenhouse I had several stacks of tires (three or four high) filled with earth. Some sources now advise against tires. Though, I can find no definitive proof that tires are a health hazard (most treated wood is probably not safe). I have changed to barrels and blocks myself for the most part.

I fill the raised beds with soil from the sunken water pit. At one stage the watermelon plants on the ground were one foot long while the plants planted in the raised beds were six feet long. That's due to the difference in soil temperatures after spring thaw. In southern latitudes there may be less variation in temperature.

Raised bed veggie growing (now mainly in the greenhouse) is a passion for me for about a dozen reasons: (less weeding, less compaction, more productions, earlier crops, and healthier , later crops, more aeration, warmer roots for faster growth, ease of access, ease in harvesting, cleaner crops, less danger of root rot, and more. My first raised beds were made with free tires.

Now I Have Barrels of Fun!

Our 50 gallon or so barrels cost is only $3 each from company who makes fiberglass tombstones! The fiberglass is drained from these barrels leaving the sides coated with a thin layer, which helps prevent rust. Some people choose to burn out the fiberglass. The top and bottom are cut out so that the roots can penetrate the whole greenhouse. The barrels are several inches apart to allow air circulation thus warming up faster. Plants at the top of the barrel cascade down the sides making it easy to pick the lush tomatoes, cucumbers, squash, melons and other crops. The plants are also tied to the rebar rods thus quickly producing a jungle of foliage all around the pathway, with cantaloupe bumping your head. All that heat and humidity causes the plants to grow like monster.

Why Do My Plants Grow So Quickly?

I play them Tchaikovsky! There are several other reasons. Moisture is optimal due to the high humidity and mulching. The narrow rebar rods I use for my greenhouses let in lots of light. And the third factor is most interesting: Soil Temperature. That's one reason plants grow so slow in the early spring, even if the air is quite warm, especially "warm" crops like tomatoes, melons and cukes. The temperature of soil in metal barrels climbs rapidly in the warm greenhouse, since the soil is way up in the air three feet high, where the warm air accumulates. (Cool air sinks to ground level.) Also, there is a very high ratio of soil exposed to the warm air through the metal compared to the same amount of soil on the ground. Several times more soil is warmed by the air than if it was at the ground level, so the roots grow fast even at night. The soil will be warmer than the air at night. The greenhouse air, in turn, is warmer than the outside air.

More Advantages of Metal Barrels

The plants are easily looked after, being at chest height. There is greater production. The plants cascade down the sides like a waterfall of fruit. Constant pruning is needed to prevent the path from being invaded by these fast-growing plants. The tons of soil in the metal barrels quickly absorb a tremendous amount of heat and release it at night. Wet soil holds almost as much heat as water. This is a good alternative to using valuable greenhouse space for water containers just to hold heat. You can have your cake and eat it too! The metal absorbs heat very fast. With soil barrels and a water-filled pathway I've found my plants won't freeze until it's below 20 degrees F. outside, even under just one layer of poly. Also, barrels are so much easier than building 3-foot high wooden containers, which will rot if not treated. Used barrels cost less than wood, are strong, and can be spaced to allow warm air between the barrels. And metal really absorbs heat. I paint them white to increase light. Black markedly decreases the light and is probably not needed to absorb heat since there is so much thermal mass already there. If you want you can paint them red and blue, which will absorb heat and also provide the plants with most of the spectrum that they need.

Playing With (Concrete) Blocks

Inside one greenhouse I constructed in the past, I built 5' high raised beds out of hundreds of concrete blocks stacked two deep without cement or mortar. I scrounged my blocks for free from houses and buildings being demolished. People are often happy to let you have them just for hauling them away. I have filled my raises beds with old manure and soil and mulched them heavily. Tomatoes and cukes hang down the walls for easy picking.

A Real Metal Tank Garden?

My latest: I drove to my neighbor's scrap yard, selected and bought six used 1000 gallon metal water tanks, each 14 feet long and 5 feet in diameter. I had him cut each tank into two 7-foot long cylinders, each 7' high and 5' in diameter. We manhandled each into my pickup truck (one per load!) and I hauled them home. I erected each of them vertically about four feet apart inside my greenhouse. Then even more work! We filled each 7' high x 5' diameter cylinder with good soil and compost, by hand, using buckets, shovels, muscles, and ladders!

Advantages Of Metal Containers

Steel walls are so much thinner than concrete blocks, allowing more soil in the bed, they store heat at night, faster heat transfer from sun and air into soil, more vertical hanging space for tomatoes, peas, beans, cukes, melons, etc. they hang down as well as being staked up. New shoots just keep forming and grow quickly downwards aided by gravity, producing clean, accessible, healthy, beautiful, bountiful fruits!

Bob's Greenhouse Tips

Pollination inside your Greenhouse

In the large rebar greenhouse, I had no problem. Probably because of the large 9 by 6 foot end vents the bees seemed to find their way in easily. And wind blowing inside helps, especially in corn pollination. You can pollinate by hand with a tiny paint brush or aerosol spray. Pollination may be a problem with small insufficient vents.

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