The galvanized raised bed project

For the last few years, I’ve been trying to make up my mind and get up the motivation necessary to design and build a few raised garden beds.  Over the winter, I finally hit a breaking point with how bad the series of 3×3′ beds that built several years ago were doing (I knew better than to use 2×12 pine to build beds, but I did it anyway).  I’ve been wanting to build a big L-shaped bed with multiple levels working its way down the slope of our yard, but man things start getting complicated when you actually start looking into the logistics of designing and building something like that.  I’ve also been moving more towards lower input gardening, especially with edibles.  Bolstered by the success I’ve seen with my peach, nectarine, and apple trees, I decided that I needed to add a fig tree to the lineup, but I wanted to grow it flat against a sturdy trellis using a technique called espalier.  The next step was to decide where exactly I wanted the garden to be and what the dimensions would need to be.  I did some measuring and set out t-posts and experimented with height, etc.

L shaped bed layout

Having developed at least a preliminary game plan, I spent some time figuring out the details of what materials I would use (should I build this out of 4x12s like my big raised beds, or something else?) and running the numbers in terms of cost, I decided to build it out of galvanized corrugated steel roofing panels.  I’ve seen a bunch of photos of corrugated metal garden beds on pinterest and finally figured I’d cave and try my hand at building my own.  My biggest challenge in designing these beds was determining how to put them together so they’d be both attractive and strong.  Then I spent a lazy Sunday relearning Sketchup and putting together a CAD model of the bed to figure out what wood measurements I needed so I could make the most efficient use of the lumber I used as well as work out design problems in the model instead of working them out with actual materials, potentially wasting them.

sketchup model

I decided to go with stained fir 2x4s and 2x6s a) because I wasn’t confident that the beds were going to look any good, b)pressure treated is about twice the price and c) there isn’t much soil contact with these beds due to the galvanized steel making up most of the surface area. Time will tell if this was the right decision or not, but if the fir breaks down, I believe I can rebuild them fairly easily with pressure treated wood where they stand.  I pre-stained the wood because it’s easier to stain everything ahead of time and then come back and touch up anything that needs touching up after the beds are built.

Each corner consisted of a 2×6 butted up against a 2×4 to give maximum support to the corrugated metal panels. They are connected with horizontal pieces that are toe-screwed into the corner pieces. The whole thing is capped with 2x4s to provide lateral support so the vertical supports and flimsy corrugated metal don’t blow out under the weight of the wet soil.  I started with the 4×4′ square bed that sits in the crook of the L because it was a smaller project that felt a little less overwhelming and I figured if I needed to rebuild it once I had done it once, it would be less dramatic to remake than a 12′ long side.  As much assembly was done on the deck as was possible.  Having a flat clean surface to work on made this significantly easier than it would have been if I was building it on a sloped surface on either wet grass or mulch.

The second phase of the project was building the complicated corner, which was the “hub” for both arms of the L, both different heights.  Building this corner took me most of a day.  I worked slowly and triple checked everything I did, and it payed off.  No mistakes! After I did all the assembly I could on the deck, I got Craig to help me carry it down to its landing zone, then spent forever making sure the bed was level and square. The uphill arm of the bed had to be built in place, but after enough fussing it came together as well.

The next step was finishing the “caps” on the uphill portion of the bed (these are necessary to the lateral stability of whole thing) and then beginning to fill it up with material.  Do you remember my post on my low-water raised garden beds?  I used the same concept in these.  I took as much old wood as I could find in the yard, primarily the frames from the old 3×3 beds I tore out to put this in.  Then I kind of went into the mode that I get into when I start deep frying something.  Maniacally searching the house for things I could deep fry – or in this situation, things that will eventually compost down.  Amazon boxes with the paper tape were a great resource.  We threw pizza boxes in there, anything that would have gone in the compost bin got chucked into the garden beds, Craig and I drink ridiculous quantities of canned seltzer water, so the boxes from those went into the beds… really anything. I did some intense weeding from the front yard and dumped all of the weed material in the beds, then threw down another layer of cardboard boxes.  Then I took everything out of the compost bins and moved it over into the garden bed as well.

The last 2 steps were getting the trellis built and filling the bed with some purchased compost.  I just couldn’t come up with enough material to fill the garden beds up.  The trellis was pretty simple.  I used more 2x4s as a place to add rigidity to the rebar reinforcing mesh that I got for this purpose. The mesh got pound-in stapled to the 2x4s and the 2x4s got screwed into the frame of the garden bed.  The place I bought my compost from has a 6 yard minimum, but I only really needed 4.5 yards of compost, so I filled the beds up very high with compost knowing that it compresses down pretty quickly.  All of my compost bins are also full of this commercially prepared compost, so I have plenty to fill in the beds as everything settles.

What’s going in the beds?  The square bed is a dedicated blueberry bed.  I have 4 blueberry bushes that seem happy.  They need a very acidic soil that most other plants don’t care for, so I underplanted strawberries.  If they survive, great.  If not, I had the starts anyway so I didn’t lose anything. The bottom arm of the L will have a fig tree planted and grown flat against the mesh trellis, and a few rhubarb plants in front of it.  I still haven’t decided whether to do dwarf raspberries in the top portion of the L, try my hand at artichokes, attempt another trellis section and grow vining plants of some sort,  or grow annuals there.   This year I have a few winter squash plants in there just to take up space till I can decide what I want to do.

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