my impression is that it'd erode ,being in constant contact with the ground and the soil inside the bed. it would never have a chance to dry. what would the plaster be? lime ? that might be hard on some of the plants i'd think.
i looked into making beds from Hypertufa a long time ago.kinda like stabilized soil(concrete,perlite,clay soil) decided in the end it was just too costly,permanent and involved, would still have to buy wood to make the forms anyhow,may's well use teh wood for the boxes.
The only recipes I have seen for hypertufa call for cement peat moss and perlite, not any sort of soil at all, and since it isn't generally considered a "Good Thing" to use cement or peat moss unnecessarilly (cement because of the processing needed to make it and peat moss because it is a non renewable resource which is a major carbon sink for the world) it's hard to recommend it. Recipes for coir instead of peat moss can be found.
In any case you don't need a wood mold, you can use nested cardboard boxes or an upside down stock tank or anything really, as long as there is some sort of release layer between the mold and the hypertufa. It will take quite a long time to dry, especially if it's large and thick walled, and the cement is caustic to plants so the thing has to be neutralized with lots of flushes of water (some use vinegar) or some such before it is planted. OTOH properly made they will last indefinitely and can be very attractive. Not sure they will help a lot with your clay soil though.
if you live somewhere you could do it, or know someone who does, you could make bricks with your clay..perhaps use the heat from making some biochar? I would guess they would last longer than simply making a clay wall with raw clay. They'd also be more easilly moved if you decided you wanted to rearrange things at some later date. You'd need to mix something in with the clay..according to Davidovits, some clay mix bricks will cure with temps achieved with just the sun shining on a black plastic garbage bag covering over the bricks. (He was talking about Africa but the temperatures in question would be achievable in the summer most places.)
posted 8 years ago
Rototill and amend the soil. and amend and amend and amend...
In clay soil, the rototiller and high pressure sprayer is your friend.
Before I heard about Hugelkulture, I was raising beds and ran outta material. I went into the woods pulled out enough straight tree limbs and trunks to make a log cabin style raised bed. I used clay that I had dug outta the raised bed area to help keep the log cabin together. Eventually, there was some erosion and wood deterioration, but I would never go back to the squared off lumberyard raised bed again unless it is close to the house... for looks. I actually get more compliments on the 'found' look of the clay/wood beds.
AND my cheap ass loves the cost of material.
posted 8 years ago
Another option is growing things in straw bales..I thought I was the only one doing that and it turns out all sorts of people are! There are lots of advantages..one being that what sort of soil you have is a lot less important and another that everything being 18 " high is a lot easier on the back. Root crops don't do all that well..and they say that corn will tip the bales over but I've grown peas. squash, nasturtiums and tomatoes (and various other flowers) in them with success. People have different approaches..one is here http://www.no-dig-vegetablegarden.com/straw-bale-gardening.html It seems that most people expect the bales to last about two years..some compost them and start new ones every year. They do tend to dry out faster than the ground does, like any raised bed seems to.
Some people make a circle or square with them and fill the inside with soil for root crops and then plant other stuff in the bales. I make a pocket of soil (compost if I have it) for the transplants and put a thin layer of compost or soil on the top..going to have to try crushed egg shell this year as I had a bumper crop of slugs in the VERY wet summer we had last year..astonishing they could find the tomatoes way up there, but find them they did
posted 8 years ago
I usually find big pots at garage sales/estate sales. Anything cheaper than that you need to go dumpster diving or make a trip out to your local landfill/dump.
Raised beds can be made out of just about anything. Used tires, toilets, old cast iron tubs, and abandoned car, I think the toughest thing about living in a high clay area is the limit to what you can build on top of the soil that will last... If you look at older cemeteries in high clay content areas, you will notice that all the head stones look like they are about to topple over. Clay is just funky to build on because it moves.
I don't think you want to build a Rammed Earth bed because it will erode on you without pouring some sort of stone or concrete foundation in first. However, if you are wanting to just experiment with making a structure, nothing beats hands on experience, especially the blisters you will gain when you forget to wear your gloves.
I make my raised beds about 8 to 10 inches off of the ground. Recently I have used the red concrete stepping stones 16 x 8's and i set them in the ground like pavers. They make a nice 4'x4' box (about). However, since I have clay in the soil, they don't set well like that and so I have now stopped burying them about 1/3 into the ground and I am now using cinder blocks with the red stones as caps. (This actually works better because I have old windows that I can place over the top of my beds and I can get an early start with planting using the raised beds and windows as a cold frame.) I just lay the cinder blocks out and plop the red stepping stones on the top like caps and then fill with potting soil, compost, and manure. Clay soils usually have more night crawlers than you ever dreamed of needing, and the raid bed can act as a cold compost pile while you grow things on top of it. Between the beds on the outside, I lay a couple inches of cypress much on top of old newspaper.
I'm in Zone 6b and the beds have worked great for a few years, but now I have accumulated 60+ old windows. My next project is to remove the garden soil and beds, and build a greenhouse in the same spot so I can grow things all year around. Maybe start dabbling in Aquaponics.
posted 8 years ago
When you say "backyard plot", it makes me think we're not discussing a huge acreage here - in which case amending it should be no incredible feat. I'd be careful mixing sand into clay; getting the proportions correct can be tricky, and too much or too little will leave you with cement. With compost on the other hand, you needn't worry much about being heavy-handed; if you're not satisfied with the soil structure after incorporating it, just keep piling it on until the desired result is achieved. Beats building beds when you already have a level, arable plot.
Go with the straw bales, we are hosting open house/strawbale garden classes every month this season, free. Once you've done it, you won't go back. Sell your rototiller and take a vacation. Mom did last year, she is 80 now. She told me one day on the phone that she weeded her garden, said it took her 5 minutes and started giggling,, well, you get the picture,, Go Bales
If you wanted something more permanent, say with benches around the planter etc, you could go with rammed/compressed earth. The earthbag or meshbag filled with clay, tamped down, dried, and plastered with some magnesium cement which is very non-toxic and actually helps improve soil minerals apparently.