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I am occasionally asked to give a presentation entitled Common Gardening Mistakes and Myths. One of the topics I cover is raised beds. During the talk I explain that (1) there are different kinds of raised beds and (2) there are circumstances where a raised bed is appropriate. I also state that I am certain the question "why is a raised bed being considered" (i.e., the appropriateness, the need) is rarely posed, and almost never objectively addressed, since well over 90% of the raised beds I see were NOT needed and about the same percent have one or more flaws, including design, craftsmanship and subsequent maintenance issues.

Let's consider the need part first. The instances when a raised bed is appropriate (not rank ordered) include (1) to make the bed easier to access (this would be particularly relevant to a person who has trouble bending over or some other physical limitation), (2) if the area has bad soil (e.g., rocky or too clayey) that is unsuitable for what it is they want to grow, (3) if the area is prone to flooding and/or it is a location that remains too wet, (4) if the soil is contaminated due to some previous human activity (e.g., chemical spill or lead based paint, and keep in mind that there needs to be a barrier between the contaminated soil and the new overload), and (5) to help create a more level planting surface (i.e., to reduce erosion and to facilitate even watering). There may occasionally be other considerations, but those are the main factors.

As for how to make the raised bed (i.e., to create the confinement):

WOOD - wood is not suitable for ground contact unless it is treated and the preservatives in treated lumber make such wood unsuitable for use with food plants. This exclusion from use for food production certainly includes railroad ties. The preservative problem can be overcome somewhat by lining the inside of the walls (the part in contact with soil) with a plastic or rubber membrane. But reality is, the lifespan of a wooden raised bed is maybe a decade. The thicker the walls the longer the lifespan with some species more resistant to decay than others (i.e., black locust would be much better for this purpose than white pine, but black locust is rarely available as construction lumber). Additionally, it is important that the sides (the walls), if wooden, must be at least 2 inches thick, and 4 inch thick lumber is better. The walls of the two beds in the top pic above are only 5/8 inch wood, which will bulged as soon as the "soil" is added, and it is untreated softwood. While this design may be attractive it is grossly inadequate. The pic was taken as soon as I saw the owner install the beds and, as I would have stated if asked, it obviously was a flawed setup from the get-go.

RECYLED PLASTIC (FAUX WOOD) - when I first considered doing this it seems like a good idea since the material is more decay resistant compared to wood. I eventually decided I did not like the look and the price of the material made it cost prohibitive.

MASONRY (with or without mortar) - most of my raised beds, and I have several, are made using natural rock but without .mortar. This method is labor intensive, and challenging due to the weight of the rock as well as acquiring suitable specimens, but I like the look, and it works. Furthermore, I have discovered that the bottom part of the rocks need to be partially sunk/buried -- doing so provides a better look and stabilizes the stone (i.e., prevents it/them from being displaced outward by the pressure exerted by the confined soil. I do not like the look of most manmade rock and most anthropic rock is flat thus prone to movement unless attached to the adjoining piece(s) with a masonry adhesive. I do not connect the fieldstone I use with mortar -- this frees me to subsequently modify (usually to expand) the raised area more easily. See middle picture above.

METAL - I have several raised beds created by using fire pit rings made of corrugated galvanized steel. These rings are one foot tall before I place them and range in diameter from 3-5 feet (see middle pic above, in this instance 5 ft wide). I DO NOT use or recommend roofing panels of the same material for raised bed walls. Invariably some part of such boxes is made of wood -- wood is not suitable for long-term soil contact -- and the design typically does not present the sides from bulging. The metal is also more likely to corrode if in contact with soil.

TAPERED (essentially wall-less) - a common misperception it that one must use some sort of material to create a vertical barrier wall in order to confine the soil. I have several raised beds created by gently tapering the soil upward away from the perimeter, thus creating a low raised mound. I often do this in concert with a perimeter of appropriately sized boulders or smaller fieldstone (see top portion of bottom pic above). The perimeter delineates but often provides little or no retention. - FYI by definition a boulder is at least 10 inches in diameter.

EYEBROWING - Related to taper but not specific to material used. This is a look I borrowed from architecture (i.e., eyebrow windows). I use this method on slopes to level the planting surface in order to prevent erosion and to facilitate watering. Doing so creates a minibed (usually employing rock) with exposure (height) greater in the front (the low side) and tapering to the middle on each side or beyond, depending on the grade on the high side (the back). The fire pit ring example above is an example. The grade on the slope (the fall) would have been six inches over the five feet from back to front. BTW, the tree in the ring is a sourwood (Oxydendron arboreum). The ring also permit me to more easily isolate water, modify soil chemistry and serves as a barrier to encroaching weeds.

CONTAINERS - a bucket can be considered a raised bed and, although much smaller than the types described above, a raised container, nonetheless. A buddy grows all of his tomatoes in this kind of raised container. Doing so allows him to have new (replacement) growth medium every year which can be useful when growing the often more finnicky heirloom mater cultivars.

Almost all of the raised beds I see, and I actively look for them, are one or more of the following: (1) unnecessary, (2) poorly constructed, (3) not leveled, (4) too big (volume) and/or (5) poorly maintained.

So, why do people jump to the conclusion that they need to create and use a raised bed and then do so ineffectively? Monkey see, monkey do. My idea, what I want to do, so that makes it a good idea. Following the lead of others, and it is frequently poor leadership. Most of the GOOD stuff you read about raised beds is written by people with limited or very limited experience and/or people wanting you to buy something. Attempting to get you to give them your money for something you may not need, and most of us are gullible. You end up doing something that was unnecessary and then trying to justify your bad decision rather than be willing to admit having madea mistake, jumping to false conclusion

Other raised bed myths include that (1) they are inexpensive (a well-constructed and suitable 4x8 bed can run several hundred dollars, never mind the fill material {the growing medium}) and (2) raised beds reduce maintenance activity, especially watering and weeding. Not only do raised beds NOT reduce maintenance they also take the area occupied by the perimeter out of play for cultivation. Moreover, frequently the ground over which the raised bed is placed is as good or better than the "soil" in the contained area about to be covered. I have also frequently observed that the depth of the "soil" in the raised bed chamber is only a few inches above grade thus obfuscating the reason.

BOTTOMLINE, there are certainly instances when a raised bed is a good idea, but it not as often as most people suspect and IF you are do so, do it right, not a chintzy thin-walled version.


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