Given the option, I can’t imagine not utilizing raised garden beds. They offer a simple and effective way to create a healthy and productive garden by manipulating the growing environment. Ideal conditions can be created for soil structure and drainage; essential keys to success.
Design the soil for structure and drainage
Native soil that is either too sandy or compacted does not hinder the raised bed gardener. With raised beds, soil can be brought into the garden and mounded up in wide rows or added to a framed structure no matter what the condition of the existing soil.
Ideally, it is best to incorporate native soil along with plenty of organic material such as well-aged manure and compost, and even store bought soil amendments. However, there are times when blending native soil isn’t practical.
In either case, the goal is to create a deep, wide growing area that encourages roots to grow down and out. Soil that is just right is said to be loamy and have good structure or tilth. An easy test for knowing when you’ve achieved the perfect mix is when you squeeze the soil in your hand; it binds together, yet crumbles apart easily when disturbed.
An equally important benefit to just-right soils in raised garden beds is superb drainage. Thanks to gravity, water wants to always run somewhere. Saturated soil and rotted roots are rarely a problem because the water is moving through and out of the bed. Fortunately, raised beds allow you to easily create the optimal combination of drainage and moisture retention at the same time by adding lots of organic matter.
Options to Contain the Soil
The choices when constructing a raised bed are many. Three of the most popular options include pressure treated lumber, non-chemically treated wood such as cedar or redwood, and recycled composite material consisting of plastic and wood fibers.
Pressure treated lumber is a popular choice because of its resistance to rot (due to an injection of chemicals into the wood), availability, choice of sizes and low cost. However, due to health and environmental related concerns by some, there are growing efforts to reduce the use of treated wood, seek alternative options and change the way in which wood is treated.
Certain woods are naturally rot resistant and do not need to be treated. Popular options include Eastern Red Cedar, Redwood and Black Locust. These varieties can last 20 years or more.
One of the newest wood alternatives on the market is composite timber, typically made of recycled plastic and wood fiber. They are designed to look like wood, built for strength and come in several sizes. The best part is they will never rot. Although the cost can seem expensive initially, when you consider they may never need to be replaced, this choice becomes a cost effective option. Look for a system that allows the plastic timbers to be stacked for any height desired such as Scenery Solution’s Frame-It-All System.
Whether you choose to contain your bed within a raised border, or simply mound the soil up; raised garden beds provide a significant advantage in creating a productive and healthy garden. Gardens that have great soil and drainage are a sure way to get your plants off to the best start. Raise beds are a quick and easy way to make that possible.
I will be building raised beds higher than 12″ due to a bad back. What kind of soil can I fill it with that can be store bought and also where can I buy that kind of soil? What should I add to it to enrich it? And in what amounts? I don’t have yard that I can dig up for the soil so I need to purchase it from somewhere.
Kimberly, I can empathize with having back issues. Here is a link for GGW episode 406, Building a raised-bed gardenhttps://www.growingagreenerworld.com/raised-bed-garden/ and another link with more information about soil. There is information about the soil and adding compost. Look for organic bagged top soil and bagged compost that is certified compost by the US Composting Council. https://www.growingagreenerworld.com/feed-the-soil/ You will get great results if you start with good soil. Happy gardening!
The soil in the Phoenix area is very hard and compact. Do you recommend tilling it first, adding mulch, peat moss, and compost…………before building the beds on top?
Hi Jeffrey. Assuming you are building mounded beds directly on the native soil, then yes, I think it is a good idea to break up the existing soil and incorporate some more organic matter into it. Then add your “ideal soil mix” as you create your beds on top. This way, roots will have a better chance of going deep and the overall soil quality will improve over time below grade.
If you were building deep raised beds (12″ or higher), I would bother with the extra work and material (even though I still did it). It really is not necessary.
A fantastic option is the use of cinder blocks. You can make an eight inch high bed or stack (staggered) two high to make a sixteen inch bed. I fill the holes in the blocks with soil and plant thyme or oregano. You do not have to mortar the blocks. Their weight will keep them in place. And they can always be rearranged to make any size bed or planter that you wish.. They will NEVER rot. I have been using these for my vegetable garden for years.