Growing vining crops on trellises can help maximize your bed’s productivity. As Powell Smith, a Clemson Extension agent in Lexington County, says, “We pay for land by the square foot; vertical space is free.”
Vining crops such as garden peas, cucumbers, pole beans, luffa gourds or cantaloupes make use of vertical space when trained onto a trellis, greatly increasing yields from a raised bed.
When trellising vegetables, keep these tips in mind.
- Vining cucumbers and beans produce over a longer period of time, yielding more production, than their “bush” counterparts.
- In addition to their practical value, trellises offer architectural interest and can be used to screen unsightly views, such as utility boxes and AC units.
- Having vegetables off of the ground reduces their potential for rot.
- Prevent the vines from shading your other crops by planting them on the north side of the bed.
- Trellises can be fashioned out of bamboo teepees or woody branches or by fencing T-posts with wire, string or other materials. Use existing structures such as deck railings or fences when you can.
- Make sure your trellis structure is strong enough to support the weight of the produce. If you trellis a heavy crop like cantaloupe or watermelons, you will need to support the individual fruits with mesh slings. Recycled pantyhose works well.
Step by step: Constructing a raised-bed garden
To construct one 4-by-8-foot raised bed, you will need:
- Three 8-foot lengths of 2-by-8-inch pressure-treated lumber
- One 8-foot length of 4-by-4-inch pressure-treated post
- 24 3½-inch coated deck screws
- Circular saw
- Posthole digger
- Cordless drill
- Framing square
1. Begin by marking out a level, 4-by-8-foot area where the bed will be built. Remove as much existing vegetation (grass, weeds, etc.) as possible by rototilling and raking out stems and roots, as well as rocks or other debris. For troublesome perennial weeds, like Bermuda grass, kill it beforehand with an herbicide labeled for vegetable gardens or by smothering it with layers of newspaper and mulch. Herbicides are only effective if the weeds are green and may take two to three weeks to work. Smothering by layering newspaper, cardboard or mulch may take as long as six months or more.
2. When the area is cleared, you are ready to begin construction. First, saw one of the 2-by-8 boards in half to make two 4-foot sections; these will be the end boards for the bed railing. Then saw the 4-by-4 post into four 2-foot sections. These will frame and anchor the bed railing. Many home centers will cut lumber to your specifications when purchased.
3. Next, use a posthole digger to dig holes 18 inches deep in the four corners, and place a 4-by-4 post in each hole. Position posts so the bed railings will fit on all sides. Using deck screws, attach the 2-by-8 rail sections to the outside of the posts, starting with the long (8-foot) rails. The tops of the rails should be 2 inches above the tops of the posts so the posts aren’t visible in the finished bed.
4. Next, attach the 4-foot end rails to each end, making sure the corners are square. Using your level, make sure all the rails are level. The bed rails should sit on the surface of the surrounding soil, with no gap between the rails and the soil. You may need to dig deeper postholes or backfill slightly to level the rails.
5. When all rails are square and level, backfill around the posts with soil (concrete is unnecessary) and tamp lightly. Your new raised bed will now be secure, stable and ready to fill with soil.
Treated lumber: Safe for your garden?
Prior to 2004, chemicals used to pressure treat lumber contained the toxin arsenic, causing concern that vegetables growing adjacent to treated lumber might take up enough arsenic to cause negative health effects in humans.
Although studies have shown that this is unlikely, lumber companies voluntarily removed these products from residential markets in 2003. Newer preservatives use safer, copper-based compounds to protect the wood. If you still have concerns about using treated lumber for garden beds, simply affix plastic or rubber sheeting to the inside face of the boards. This will prevent preservatives from leaching into the bed and being taken up by plants. Also, naturally decay-resistant woods, such as cedar and cypress, are available, but they tend to be more expensive.