When I was a baby gardener many years ago, I bent and stretched and knelt and dug furiously for hours in my backyard. Tired and happy, I would go to bed, and joyfully do it all over again the next day.
Many Tylenols and creaking bones later, the work became less fun. Then I discovered raised garden beds. Desperate to claim the last sunny spot in my backyard for a garden free of the maple roots that penetrated the entire lawn, I built two small raised beds — and was thrilled to grow the best tomatoes of my life. Root crops like carrots and parsnips grew effortlessly in the deep, loose soil, and I even got a small crop of sweet potatoes.
Raised beds — basically an open soil-filled box without a bottom — are a gift to aging and handicapped gardeners, and to people with poor soil, rabbit issues and root-filled or excessively wet yards. While there's cost and work at the start — those beds must be filled with soil — over time, gardening in raised beds is low on effort, high on reward and easy on the back and knees. Because the soil in raised beds tends to warm earlier in spring, they extend the gardening season. And raised beds can help deter pests like rabbits, which are rarely willing to leap more than 18 inches into unknown territory.
Start by picking a level, sunny spot for the new bed. Make sure you leave enough room to easily walk between the new bed and any nearby walls, plants or other gardens. If grass is growing around the bed, leave a path wide enough for a mower. And if the bed is near other gardens, make sure your wheelbarrow and other equipment have room to maneuver.
A raised bed can be as big or small as you want. While most are 4 to 10 feet long, 4 feet is a good maximum width. You want to be able to easily reach the center of the bed to weed and plant.
Height is up to you. Raised beds a foot high have enough depth for growing most vegetables. (If you have trees nearby, be prepared to turn the bed's soil over each spring; a web of hairlike tree roots will eagerly infiltrate your garden over the summer.) For most gardeners, 18 inches is a nice height to reduce the need for bending. Raised beds between 2 and 3 feet high work well for people in wheelchairs. Gardeners who want to stand as they weed and plant can build raised beds as high as they want. For people in wheelchairs, raised beds can be put on sturdy stilts to permit easier access.
Wary of using treated wood that might leach chemicals into my food crops, I built my first raised beds out of cedar, screwing the side boards to 4-inch-square corner posts. The boxes were lined with landscape fabric to prevent soil from leaking between the boards. Cedar is not cheap, so I was disappointed that after seven years the corner posts in the 18-inch-high boxes were rotting. Even cedar decays next to wet soil.
Today, methods of preserving wood have changed, and treated wood is safer than it used to be. Still, cautious gardeners line the insides of their raised beds with impermeable products like plastic sheeting to prevent any contact between wood and soil. If you're willing to switch out wood every five or six years, you can use something cheaper, like untreated pine, to make your raised beds.
With the increasing popularity of raised beds, kits are easily found in big-box stores and online. Do-it-yourself gardeners have used stacked concrete blocks and galvanized steel stock tanks for raised beds. Large holes have to be drilled in the bottom of the tanks for drainage, but they will last a very long time.
When my original raised beds needed to be replaced, I bought 28-inch-high beds with corrugated steel sides supported by treated wood frames. No vegetable needs soil that deep, but the height allows me to garden without bending. One caveat: If the beds are filled totally with soil, that's a lot of shoveling and lifting.
I was advised to fill the bottom with debris like tree trimmings, pieces of stumps or old paving bricks to save work. I did that. While the buried wood will eventually decay, putting a layer of harmless garden waste in the bottom saved me some work as I filled the new boxes.
Once a raised bed is in and planted, you can sit back and watch things grow. The only real work is making sure plants get enough water — raised beds dry out faster than in-ground garden plots — and in picking out any tiny weeds.
While it's easy to step into a low raised bed, don't do so after planting. One of the advantages of a lifted garden bed is to keep the soil fluffy and loose, giving plant roots room to expand. This is especially important if you're growing root crops like beets, parsnips or carrots. As soil settles over time, you'll probably need to top off your raised gardens with additional soil in the spring.
If you need help with designing a raised bed, there are tons of ideas on the internet. Here's a simple plan for a basic raised bed that makes it easy to replace boards when they rot. www.goodhousekeeping.com/home/gardening/g20706096/how-to-build-a-simple-raised-bed/
Mary Jane Smetanka is a Minneapolis freelance writer and Hennepin County Master Gardener.