‘Raise’ your gardening expectations
Published May 15, 2013
WARREN — Raised bed gardens are more than just eye-catching boxes of plants in your yard. They’re ergonomic, easy to plot and offer many advantages over traditional gardens when it comes to dealing with weeds, managing soil conditions and even extending the growing season.
They’re also easy to build out of just about anything, depending on how fussy you are about the final appearance and the source of the building materials.
If you’re looking to build a single frame or an array of beds this year, the clock is ticking. But if you know what type of bed you want and are even just a little handy with tools, there is still time to get going this season.
Building the beds
“It’s a pretty simple procedure. There’s a lot of information on the Web,” said Charlene Molnar, a horticulture advisor with the Michigan State University Extension in Oakland County.
Molnar said that what works best is different for everyone.
Without question, the most durable option for wooden raised garden beds is pressure-treated lumber. What’s available on the market these days is no longer treated with chromated copper arsenate, and experts say it’s safe — but other treatment processes are still an issue for some gardeners concerned about contaminating beds that are used to grow food.
Some people just prefer natural, untreated wood, and that’s a cheap option for a rigid-frame raised bed, although it won’t last as long as pressure-treated lumber. Fir and pine are the most inexpensive choices and both are readily available at most big-box home improvement stores in Michigan. But since the beds are filled with moist soil and contact the ground, those made of fir or pine won’t last as long as cedar, a naturally rot-resistant wood that’s significantly more expensive.
To make untreated wood beds last longer, consider lining the inside with plastic sheeting to prevent soil contact. Another money-saving option, especially for those making beds at least two boards deep, is to use a naturally rot-resistant — and again, more expensive — wood on the base level, with a cheaper alternative higher up.
You can also use hay bales, cinder blocks and plastic or composite building materials to construct raised beds.
However, Molnar said it’s best to use a rigid frame. Hay bales might not hold the soil as desired.
She also cautioned that cement blocks could leach lime into the soil over time, altering the pH.
“You want your soil pH for a vegetable garden at about 6.5. You don’t want anything that could leach,” Molnar said. “It’s not toxic, but it could alter the soil chemistry.”
Again, it all comes down to your budget, what you want the finished beds to look like and your level of fussiness over the building materials.
Do some research and make a choice that you’re comfortable with. If you’re concerned about the soil’s pH, get a test kit from the MSU Extension.
As for the size of the beds, Molnar said the best advice is to keep them manageable. A 4-by-4-foot square bed is perfect for a small herb garden, or an educational garden for the kids. Beds kept at about 4-feet wide are easier to maintain from anywhere on the perimeter. But they can be built at just about any length, depending on your space limitations, desired garden yield and materials used.
Wooden beds can be assembled with deck screws or lag bolts, depending on the size of the frame’s pieces.
Ideally, one of the goals of raised beds is to make gardening easier. Pick sizes that are right for you and your family and not overwhelming. The finished raised beds should be easier on those tending them because they’ll require less bending over. They can also be built with seating on the edges. If you’re building with wood, use a 2-by-6-inch board as a bench on one side, supported by 4-by-4-inch posts secured to the side of the bed.
Building the soil
There are nearly as many options for building the soil in your raised beds as there are for building the beds, themselves.
An online search will reveal special formulas — including a recipe of compost, peat moss and vermiculate (a mineral used to lighten heavy soils and promote healthy plant growth).
Some people simply use a mix of leaf compost and sand, while others include topsoil, manure or a combination thereof.
Dave Ross, of The Home Depot, who captains his store’s Team Depot crew through The Home Depot Foundation and has overseen the construction of several community gardens in Warren, said he favors a compost-to-sand ratio of 2-to-1. He recently also added six 40-pound bags of manure/humus to each of the 44 4-by-12-foot raised beds, each about 8 inches deep, at the new Lord of the Harvest Christian Fellowship community garden at Schoenherr and Toepfer.
Molnar said she’d recommend simply adding 25 to 30 percent compost or other organic matter to topsoil for a raised garden bed.
But again, the soil choices for most gardeners come down to cost and availability. Properly composted material is readily available from many municipal sources at no cost and is an excellent base for a raised bed garden.
If you need material in bulk, a landscape supply company can deliver mixes of compost and/or peat and sand at relatively affordable prices.
Smaller beds can be filled with bagged materials from the home improvement store or nursery.
The idea is to keep the soil light, full of nutrients and good for drainage. That promotes healthy plant root growth and is easier to weed and manage.
Raised beds are a work in progress, so the real benefits of the things you’ll add to the soil might come further down the road. Regularly adding organic material — manure, humus or compost — will increase the soil’s nutrients and will give your plants what they need to grow.
Of course, with good drainage comes the need to water regularly. Make sure the soil stays moist to avoid harming your plants, especially in the hottest summer weather.
When you’re ready to plant, a properly built raised bed garden will be ready for any plants you’d typically put in the ground. Look online for creative planting solutions well-suited for raised beds, including the popular square-foot gardening method.
Raised beds put the power in the hands of the gardener. You’ve chosen the materials. You’ve built the soil. You’ve made it easier to manage your garden.
And now, you can make the beds truly your own by adding a few finishing touches.
Well-drained soil that’s full of nutrients is paradise for plant growth. So why not extend your growing season by several weeks?
If you’re building beds from wood, consider installing short sections of 1-inch PVC vertically on the inside corners of the beds and about every four feet along the bed’s length. Use the mounted PVC sections to hold arched spans of half-inch CPVC material — which is more flexible — that’s a perfect frame for a rudimentary greenhouse when covered with plastic sheeting.
You can also use the frame to install a critter fence, or to mount a custom trellis system for some vegetables.
Raised-bed growers may also want to use soaker hoses to ensure proper irrigation. Sections of these hoses that slowly leak water into the soil can be wound throughout the bed and used as needed to keep plants happy.
Landscaping outside of the beds should be designed to keep weed growth at a minimum. One option is to install landscape sheeting to prevent weed and grass growth, covered by a good layer of wood chips or mulch.
Molnar suggested a good way to learn more about raised beds is to do an advanced Internet search for “raised beds,” narrowed to sites with domains ending in .edu. She said that would provide access to science-based knowledge compiled by various university extensions across the country dedicated to horticulture education, including the MSU Extension.
For more information
The MSU Extension provides a variety of resources for gardeners, including phone hotlines in both Oakland and Macomb counties and a statewide garden line.
In Macomb County, call (586) 469-5063 between 9 a.m. and 4 p.m. Monday, Wednesday and Friday, April through November.
In Oakland County, call (248) 858-0902 between 8:30 a.m. and noon, and 1 p.m. to 4:30 p.m. Monday through Friday.
The MSU Extension’s statewide garden hotline is available year round from 9 a.m. to noon and 1 p.m. to 4 p.m. at (888) 678-3464.
The MSU Extension also provides information for gardeners through its website at http://msue.anr.msu.edu.
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