Greenhouse Renovation Plans II
As with any plan, things change. This season I was distracted by bee opportunities and had to shuffle my deck to do a couple of emergency (as in they would be exterminated otherwise) cutouts, which meant building hives and planning my apiary. I have 6 hives being assembled to expand that little apiary and the bees are happy. But, the greenhouse renovation didn’t proceed as planned. But, that was a good thing.
There are always better ways to do things out there and knowledge is power. Under the mantra of work smarter, not harder, I’ve always kept my eyes out for simpler alternatives. This pit greenhouse is destined to become my little tropical jungle, with my exotics planted in the bottom, and with landscaping and even a water-feature. How that happens has been in a bit of a flux as I explored in depth several alternatives.
The latest alternative came about with the discovery of a bender. I had originally gotten the idea of just buying a hoop-house kit and covering my current pit at least temporarily with a regular hoop greenhouse. However, at $1900, it wasn’t cost effective for the size of pit that it would cover. And in my research quest, I chanced across a tubing bender specifically designed for bending fence top-rail tubing for use as hoop-house components. The bender is ingeniously simple and the brainstorm of a like-minded DIY’er who couldn’t justify buying something that he could possibly make himself.
Given my job as the IT manager at a hardware chain, I have access to plenty of top-rail tubing and other goodies, not to mention some scrap top-rail tubing on my property I can experiment with. This opportunity is too good to just pass up therefore and I set to planning things further to see if it would be feasible.
However, a full height hoop-house over my pit would negate some of the earth-mass benefits, so I’ll have to improvise. Rather than making a full height hoop-frame, I came across a hoop-frame that had a curved top and straight walls and the idea of just chopping the walls shorter came to me. After all, I already have 8′ of pit - so the hoop-house doesn’t need to be full height. With much shorter walls, I can keep the air mass mostly within the pit itself.
This is what I’ll use to cover my current pit next year - it’s too late this year so I’m using my current cover and everything is already nicely tucked in for the winter. But - that’s just the beginning. I have ready access to backhoe equipment and still want my larger tropical jungle. After I get the cover done I’ll start working on the next generation of the pit-greenhouse.
A rough sketch of the greenhouse upgrade.
This generation will be 30′ wide, and 80-100′ long. Same 8′ depth as the current pit. But, I’ll have accommodation for a rammed earth riser to increase the headroom. I did a little sketching and came up with a rough plan to accomplish this - and it’s actually doable! I may need to build a custom hoop-bender for the project, but that’ll be trivial. The hoop will be made of four 10′ sections of fence top-rail tubing and be curved to give 7′5 additional headroom when set on the ground. That’ll give me a total of 15.5′ headroom, which will be sufficient to plant most of my trees in the ground.
However, I’ll be planting a couple of coconut trees too. I want to give them room to grow and produce before having to replace them, so I’m planning a rammed earth risers made of soil with a bit of Portland cement that will go around the Northern, Western and Eastern perimeter of the pit. The Southern exposure will have vertical tubes instead and be glazed - maximizing solar exposure during the winter and reducing the Southern-wall shadow footprint. These risers can actually be built after the fact as the greenhouse cover will be attached to a footer that will be able to be raised and the risers installed under it, so the first incarnation of the cover will sit flat on the soil, then as my coconut trees get taller, I’ll build the risers and lift the cover higher to increase the headroom. My other tropical trees will be kept pruned shorter to make management and harvest easier.
With the earth-mass benefits and earthen risers, I don’t expect to have to actively heat this greenhouse. I may still incorporate solar-water heating and tubes snaked just under the soil to give it an edge over the really cold days of winter tho. The cover will be 48′ wide and actually fairly affordable - a 4-year poly with IR features to help retain heat. I plan to roll up the cover every Spring, and deploy it every Fall to increase it’s life and give the plants inside exposure to a good growing season and fresh rain every year.
The sandstone floor will be broken up and I’ll mix in amendments to convert the fine white sand into soil then plant my tropicals right into it. I’m thinking a bit of colloidal clay for phosphorus, some agricultural lime, perhaps granite and volcanic dust, powdered charcoal and lots of organic matter. With the floor of the pit so close to the water-table, I don’t expect to have to irrigate much, if at all, but I’ll be prepared to if I need with a full compliment of drip tubing.
The tubing that would cover the current pit will be re-used to expand a banana greenhouse I’m also planning specifically to grow bananas to harvest maturity, so nothing will be wasted.
Stumble it!