Raised beds

As you can see from past year's gardens I do raised beds. There are many reasons why raised beds are advantageous and I won't go try to explain them now. This isn't a how-to site it's a chronicle. If you want to know the advantages of raised beds there are innumerable web sites and books about such things. I was first turned on to them by the TV show "Square Foot Gardening," it's no longer on the tube but there is a book of the same name by the host and creator of the show, Mel Bartholomew.

I have been pondering just how I shall construct the raised beds in the new garden. For the New Egyptian Garden I bought the cheapest 1/2" plywood I could find, cut it into 2' X 4' sections and painted it white with a non toxic paint. When I pulled the down many had started to rot. I think I may have been able to get another two years out of them if they had been left undisturbed but some would definitely have rotted through in that amount of time.

I have been weighing the options and scouring the net and books for various materials. There are advantages and disadvantages to all of them. I want something that will last and look good. However the first priority is that they must function well, appearance is secondary. Ease of construction and cost are also major considerations.

Metal:

I found a couple sites where people had used corrugated steel and recycled diamond plate. While durable and strong metal has two big disadvantages; it is not as easy to work with as wood and it has no insulation factor. Indeed it is an excellent conductor of heat. This means that when it is hot and the sun is beating on it the plant's roots that are in contact with it will die and it will heat the soil excessively thus drying it out.

The bed at right looks more like a watering trough on a stock farm than a raised bed. Indeed, I believe this bed was being used for some industrial agricultural application.



Plastic:

Corrugated composites like fiberglass and other plastics are out of the question, particularly in an organic garden, because plastics always shed small amounts of toxic chemicals called plasticizers. And, like metal there is almost no insulating value. The synthetic deck materials, like Trex, (above) would have good to excellent insulating value but again, they are plastic and will shed toxins.


Stone and concrete:
 
a. Stone would certainly be pretty but the cost and labor makes it prohibitive. I might consider it if the garden were located someplace like New Hampshire where there is lots of free stone laying around free for the taking. In addition the walls would have to be pretty thick. This is good thermally and even though I have lots of space I don't want to use up a lot of it with raised bed walls that are nearly a foot thick. Concrete block and brick has the same drawbacks.


b. Concrete is a possibility. It can have an insulating factor if mixed with something like vermiculite or pearlite but I have never worked with concrete and it seems to me that these comparative light materials would float to the top of the wet concrete before it sets. Building the forms and casting the bed frames sounds like an awful lot of work as well. They certainly would be durable and might not look too bad. Concrete can be made in many colors and can be patterned to look like stone, brick or whatever. It's worth thinking about and doing some more research.





Very attractive but holy smokes! It looks like an awful lot of work.








Wood:
Wood seems to be still the best bet. It's insulating value, ease of construction, appearance and cost put it over the top.

a. Dimensional lumber: This is usually spruce, pine or fir.
It's a pretty good bet for this use. It's sole green and kiln dried. It's beyond me why anyone would but green wood and it's no good for this use either as it we want to keep water out of the wood to prevent rot.



b. Sheet wood. I use this a lot in my trade so I know more about it than the average bear.
1. Plywood: There are many grades of plywood; construction grade, cabinet grade, marine grade, etc,. Cabinet grade is just too expensive. Marine grade seems like it should be the logical choice as it has waterproof glue but it is also expensive and the construction grade that I have used had no problem with de-lamination as, I suppose, the glue is at least water resistant as buildings, of course, have to resist the elements. One might worry about the glues used being toxic but as I'll be painting it and the glue is inside the sheet - only wood is exposed at the surface - it's toxicity is not worth worrying about.

2. Particle board. This term describes the classic particle board which looks like it is made from common sawdust (because it is) but also describes flakeboard, oriented strand board and medium density fiberboard. These materials are not a consideration for use in gardening mostly because they absorb water like a sponge and have too many toxic chemicals in them.

3. Other solid woods:
I'd use teak, mahogany, redwood or eucalyptus if I could get it cheap enough but one would have to be rich to use these woods to make raised garden beds.


Cedar is a good choice as it is rot resistant and a lower grade, not acceptable for cabinetry, might be fairly inexpensive. It might be worth checking into. Pine and other inexpensive softwoods are no cheaper than dimensional lumber as far as I know but that's another thing I'll have to check in to. It may be cheaper to use one 10" by 1" pine plank instead of two 2 X 6s which would in actually measure about 10" together. Again, I'll check.

This wood looks like red cedar. The brackets are a kit from a catalog and they are, like most gardening catalog stuff these days, expensive. Between them and the red cedar someone must have very deep pockets.The example on the upper left looks like white cedar. It also looks pretty pricey.