You have caught me at a bit of word play here. The word radical’s first definition in the dictionary is “from the roots, going to the foundation of something, basic.” Raised beds are a basic gardening concept that are easy if you just keep in mind a few foundational ideas. Let’s group the discussion into these categories:
Reasons – Raised beds are a good way to keep your garden orderly, to cut down on the prep work every spring, make watering more efficient, and can extend the growing season.
Although you can have much of the benefit of raised beds simply by forming them out of the soil, solid retaining walls are useful. They keep the soil in place better, make it easier to keep pathways clear, and can help the soil warm up sooner in the spring. Such walls can help use the space most efficiently because you can plant right up next to the border, whereas with simply a raised dirt mound, you can’t count on the edge holding together.
Clearly designated borders also help keep everyone, including the dog, from accidentally walking on the beds by making paths obvious. A garden bed thus protected from compaction is not in need of any yearly tilling. There is no need to wait and plant until the soil has dried enough to till. Since you don’t need to make rows with a rake, either, sunny spring days can be spent getting right to planting. The visual interest of other material in the garden is nice, too.
Raised beds can be readily modified to protect plants from frost or scorching heat, by attaching wires or PVC pipes in ways that will allow for quick and easy covering with appropriate insulation or screening. Either of these things can extend the growing season of specific plants. More technical modifications could make a raised bed double as a cold frame. I have also made wire covers for my raised beds to keep the cats from digging in them when the seedlings are small and vulnerable.
The orderly design of raised beds makes spot-on watering more possible for two reasons. First of all, if your raised beds are permanent, you can make adjustments to your irrigation methods to give easy access to sources. My husband added faucets at the ends of several of my raised beds, which means I don’t have to drag hoses around as much for watering. There are ways to do similar things with above ground plastic piping. The distinct borders of raised beds will also help to guide watering practices so that little is wasted watering pathways.
Construction - To build raised beds you mostly need to keep in mind two important measurements:
- The width of the beds
- The width of the paths between the beds
It is important to be able to reach the middle of your raised bed from one side or the other without walking in them. You don’t want to be compacting the soil. The pathways are important for getting yourself and equipment between the raised beds. You want your pathway to be wide enough for your favorite wagon to fit. If you want your paths to be grass, your lawnmower needs to fit. Possibly, you also want to be able to arch a certain type of trellis from one raised bed to the other and the path needs to be a certain width for that to work well.
All other measurements are more a matter of personal preference. It doesn’t really matter how long a raised bed is, but making it longer than the planks you are using means a little engineering. The height of the raised beds should be at least a few inches tall, or what is the point of building it; but if it is too high that means more shoveling to fill it, and more difficulty with digging or spading in the future. Too high of an edge means you can’t get the same leverage and strength from you lower body when spading out weeds or trying to dig root crops. I like my raised beds to be about 10 inches tall.
Materials are the next important question. You want something that will stand up to heat, moisture, and the inevitable jab with a shovel. My husband used untreated redwood planks for my first raised beds and they lasted 20 years. We recently upgraded them using cement modules that he designed and made. These should last longer than we will ever know. You can see in the photos how the ends of each module overlap and are held in place with rebar. We also had fun imprinting the cement with leaves, flowers, feet, and writing in it.
Metal of rust resistant composition could last a while, but might risk heating up too much mid summer. However, I have some metal boxes that were picked up for me at the recycle yard that have sides with holes in them. True, dirt leaks out sometimes, and a zucchini growing through a hole is compromised, but they are whimsical and I love them. Click here to read about more junkyard container gardening and raised beds.
Plastic products might be tempting for longevity, but anything with plastic is more prone to harbor moisture in ways that rot roots or attracts things like slugs and pill bugs. I have never had raised beds made from plastic, but I wonder how they might break more completely if stabbed with a spading fork, whereas if wood gets a hole it survives relatively intact.
Straw bale “raised beds” are something I have tried three times. I put the quotations in there, because while the straw bales have some height, they can’t be filled with soil the same way other materials can. The most common way I read about, and tried, was to arrange them in a square, then put garden soil in the small space in the middle. However, the idea was to plant in the straw bale itself and let it compost around the plant. This is not what happened for me. Maybe it is a southern Idaho issue, where the climate is so dry, but I could not keep them adequately watered. Just using straw bales as a border would increase the width of a raised bed impractically. It is probably more heavy lifting than most people car for compared to other good material options. The straw bales did finally compost, but not in a way that worked as a raised bed. I now have lumpy piles of semi-composted debris in those spots, and have been able to grow some things on them, it’s just not pretty.
If you have any critters that might ravage your garden from underground, such as gophers or rabbits, you may want to line the bottom of your raised beds with some heavy duty wire. This might make weeding or digging root crops more challenging, and a deeper raised bed may be useful in these cases. However, you would never want to line the bottom of your raised bed with plastic. This would inhibit drainage and you risk creating a series of ponds.
Corners are the biggest engineering challenge for building raised beds. This can be dealt with by simply butting the long boards up against an end board, then stabilizing all the wood with rebar stuck in the ground in strategic places. Another fun idea are these metal corner guides that boards can be slipped into. Click here to learn more.
Extending the length of a raised bed can be done with an extra piece of wood and more rebar, as in the photo below
It is probably not immediately necessary to do something to the paths between the raised beds, but it could be helpful to have thought about it ahead of time. Leaving them as dirt means no mowing, and no worries about spilling over the side, but does mean more weed management. You might try using materials such as cardboard, old rugs, or grass clippings to keep weeds down. Unfortunately, some pesky insects like to hide under such coverings. Of those three things, I like grass clippings the best because they don’t look trashy and compost into the ground with no issues such as ink or staples.
Lawn is pretty and soft, and keeps down weeds, but means more edging to keep it from maturing and reseeding into your garden. Lawn paths can also make watering more complicated, as it typically needs to be watered differently than gardens. Plus, raised beds could block sprinkler coverage for the lawn, resulting in dead spots.
My final choice around my main raised beds was pavers. This was done by putting down heavy duty weed fabric and pea gravel, then arranging pavers. For the very outer edges of the whole garden I needed to keep grass from growing in, so some pavers were placed sideways at a depth to block this. If we had had this plan from the beginning, I could have made more effort to level the paths. One other wider path are flat rocks on sand. Pavers do mean I have to be more careful about what plant matter and dirt collects on the path, but it has helped with weed control a lot.
Maintenance - I’ve already mentioned the maintenance issues of paths. I have also referred to replacing raised bed borders due to decay or destruction. The only thing left is to consider what needs to be done for the soil. It is, of course, helpful to go ahead and fill the raised beds with decent soil once they are built, but I recommend not filling it to the top. You want to leave room to layer compost and/or grass clippings for weed control. You also do not want to be constantly struggling with the dirt spilling when you dig or weed.
The soil might look like it is settling a little every year, but that could be due to some nutrients being taken up in plant growth or what clings to roots when it is removed. I think it is to your advantage for the reasons given in the above paragraph. A lowering soil level, even if it is partly due to settling, does not mean it needs to be tilled. I haven’t tilled my garden in several years, preferring to let the life within the soil remain undisturbed. I haven’t even gotten around to adding compost to every raised bed year after year, though they all do get a layer of grass clippings for mulch, which does decompose. The result is that the soil in my raised beds is quite crumbly. It stays diggable later into the fall, after other soils around the yard have frozen. It thaws sooner in the spring for any remaining clean up and easy planting of cool season crops. Since raised beds are still regular dirt and connected to the ground, there are not the same issues as with enclosed container plantings. Maintaining it is the same as for basic gardening, only easier.spring for any remaining clean up and easy planting of cool season crops. Since raised beds are still regular dirt and connected to the ground, there are not the same issues as with enclosed container plantings. Maintaining it is the same as for basic gardening, only easier.
The only other chore is to train or prune growing plants so that they don’t overcrowd your paths. Space issues are nothing unique to raised bed gardening, but the borders make it more obvious. The usual culprits are vining plants, like tomatoes or zucchini, but heavily producing peas or wind whipped corn stalks can be uncooperative, too. Frequently pruning or supporting the plants is good for them, and saves produce from being eaten by ground bugs. Raised beds provide a foundational structure to work with and get this done.
I hope these radical suggestions about raised beds inspire you to try building your own. It doesn’t have to be complicated, but there are options for making it creative and beautiful. The effort to build them is similar to what it would take to form rows, but it lasts for several years. That’s radical results.