Vegetable Gardening In Raised Beds

Filing raised beds with soil high in organic matter increases aeration. Courtesy Bonnie Plants

Filing raised beds with soil high in organic matter increases aeration. Courtesy Bonnie Plants

When we moved to our home in Alexandria, Virginia, I knew that in order to grow vegetables, I would have to create raised beds.

The backyard was spacious, but over the 40-year life span of the house, the rain had created such dips and slopes that the lawn was uneven, the clay soil was compacted, and the water drainage was very poor. Building a frame and filling it with new soil high in organic matter would increase aeration, thus allowing roots to penetrate deep into the soil. This would create lush growth and higher yields of vegetables. Plus, water and fertilizer would be contained within the four walls, minimizing waste and run off. The beds would define the space for vegetable gardening separate them from the kids’ play area, and help remind the lawn service not to mow down the lettuce.

When I was ready to start the vegetable garden, I read Christa Carignan’s blog, Calendula and Concrete (cc-calendula.blogspot.com). While Christa and her husband lived in DC, they grew vegetables in a community lot for six years. In 2007, the Carignans bought a house in Montgomery County. Christa knew she would have to grow vegetables in raised beds.

“There was no dedicated space for vegetables in the backyard,” says Carignan. “The soil was heavy with clay and we had spots where the rain created puddles. Creating raised beds would help with the drainage problem.” After she and her husband moved in, they built one raised bed that fall to hold the plants from the community lot. The following spring, they built three beds for the vegetables.

Raised beds have many benefits and uses. Courtesy Park Seed Company

Raised beds have many benefits and uses. Courtesy Park Seed Company

Concerned that the clay was too impenetrable for vegetable roots and that the grass weeds would grow throughout the crops, they first rented a sod cutter and removed the top three inches of lawn. They then dug up the soil underneath to loosen it for vegetable roots and better drainage. From the local hardware store, they purchased one-inch thick, eight-inch wide, 10-foot long pine boards.

“The most rot resistant woods are hemlock and cedar,” says Charlie Nardozzi, senior horticulturist with the National Gardening Association, an online gardening resource (garden.org). “Everything eventually rots but these should last ten years. You could use pine, which is less expensive than hemlock and cedar, and apply a natural, rot resistant stain.

I caution against using treated wood, because the chemicals will leak into the soil.”

In the mid-Atlantic, it is easy to locate one-inch pine boards at the local hardware stores in six or eight-inch widths. Cedar is more difficult to find. Upgrading your wood to two-inch boards will prevent bowing in the middle due to the pressure of the soil; otherwise, posts may have to be inserted every couple of feet. Lumber stores, not the big box hardware stores, sell two-inch cedar in six and eight-inch widths. The length is optional but the longer the boards, the more likely they will bow if there are no posts. A length of six to eight feet is ideal and a bed width of three to four feet is best for being able to reach all the plants across the bed.

“A depth of eight to 10 inches should be plenty deep,” recommends Nardozzi. “If the depth is eight inches, you don’t have to remove the sod. If you have perennial weeds, you may want to lay down landscape fabric to prevent the weeds from growing up through the soil.” Gophers and moles may be deterred by nailing a sheet of hardware cloth or chicken wire into the bottom of the frame.

Raised beds keep water and fertilizer contained. Courtesy Christa Carignan

Raised beds keep water and fertilizer contained. Courtesy Christa Carignan

To assemble the wooden planks, first place them on a hard surface like the driveway. If a wood preservative is to be used, first paint the boards and let dry. Wood screws, at least three inches long, are recommended for better strength and durability than nails so a power drill will be needed. Depending on the width of the board, at least two, maybe three, screws will be needed at each end of the board. “My husband used screws and a power drill to put the boards together,” explains Carignan. “He put metal brackets on the inside corners where the boards met to hold the pieces in place.”

An alternative is to buy metal corners. Each end is inserted into one side of the corner and plastic caps are placed on top of each corner. The wood is fastened to the corners with screws and a screwdriver. These corners, the end caps, and the screws are available as a kit from several mail order companies (see “resources”). After the frame is assembled, it will be heavy and awkward so two may be needed to carry it over to the site. If the site is not level, dig a trench under one side.

Before Carignan created the beds, she first determined the best site in her backyard. At least six to eight hours of sun are needed for vegetables. “We observed how the sun passed through and we learned how to orient the beds to get maximum sun exposure,” says Carignan. Unfortunately, the spigot was at the front of her house, but she was able to buy an extra long hose and plans to install rain barrels in the future. Another option is to invest in drip irrigation lines or a soaker hose.

To create paths between the beds, Carignan obtained wood chips (free!) from the Montgomery County department of public works. “I like the division between pathways and planting space,” she says. “Raised beds also help keep the soil that you are trying to improve in place.” Because she had three beds to fill, she contacted Pogo Organics to have a truckload of topsoil and compost delivered to her home. Depending on the number of raised beds being built, it may be more cost effective to have a topsoil company deliver a truckload than to buy many bags at a local gardening center or hardware store.

Cedar raised beds like this one are available at places like Gardener's Supply Company. Courtesy Gardener's Supply

Cedar raised beds like this one are available at places like Gardener's Supply Company. Courtesy Gardener's Supply

Organic fertilizers, such as fish emulsion, may be added to the soil in the beginning and even throughout the summer, as vegetables are very hungry plants. Carignan continues to amend her soil by adding compost every year from her own compost bin.

After the bed is watered and vegetables are planted according to recommended spacing, it should be mulched to conserve moisture and prevent weeds. When a spring vegetable is harvested, plant a summer vegetable in its place, and a fall vegetable at the end of the summer.

“At the end of summer it is best to pull out the summer vegetables and put them in the compost bin (unless it is a perennial vegetable such as asparagus),” suggests Nardozzi. However, if the plant is recognizably diseased, throw it away in the trash.

But the gardening season does not have to end when summer does. Cool weather crops can be harvested throughout winter by using row covers. “Row covers can extend the gardening season for a month or so on either end of the growing season,” says Nardozzi. “The key is to start the cool season crops in the summer so they are mature when winter arrives. You really are just harvesting what is mature.”

The other option is to remove the vegetables and grow cover crops such as annual ryegrass, winter wheat, and winter rye. The seeds are sown in the fall and the grass stays green all winter long. In the early spring, the grass is shoveled up and over to further enrich the soil with nitrogen. The trick is to turn them over three to four weeks before planting so the nitrogen has a chance to break down.

“This fall, when I took the squash and other plants out, I planted winter rye and hairy vetch as cover crops. That is another way we are amending the soil,” says Carignan.

“We love having fresh vegetables we grow on our own,” explains Carignan. “It is great to be able to go out to the garden and pick fresh vegetables and herbs.”

Peggy Riccio is a Contributing Editor for ChesapeakeHome.

Contacts:
Calendula and Concrete: cc-calendula.blogspot.com
National Gardening Association: garden.org or 802-863-5251

Resources:
Bonnie Plants: bonnieplants.com or 800-345-3384
Durable Plastic Design, LLC: orcaboard.com or 425-883-2570
Gardener’s Supply Company: gardeners.com or 888-833-1412
GREEN Culture, Inc.: composters.com or 877-20-GREEN
Park Seed Company: parkseed.com or 800-213-0076
Pogo Organics: pogoorganics.com or 301-774-2968
Raised Garden Beds, a division of IP Woody’s Creative Woodworks:
raisedgardenbeds.com or 800-265-1209
W. Atlee Burpee & Company: burpee.com or 800-333-5808