Get Growing with Raised Beds

Wednesday, December 15, 2010

·         Raised bed gardens with semi-permanent sides have several advantages. There's little digging to do and the gardener gains control over soil, water and sunlight. Here's the basic process:Using 2”x6” or 2”x12” boards, you can build boxes one or two boards deep. Any size is possible, but 4’ wide puts the center within easy reach. Limit the length of each box to 8’ for stability. There are several ways to anchor the boards, but consider that you may want to disassemble the boxes to move them or work the soil occasionally. Bolts work well. Use 4”x4” posts for the corners, cut long enough to sink 4” into the soil and come up to the top of the bed.

·         Lay out the bed dimensions using string or spray paint. Start on one side and turn a shovel’s depth of soil, tossing it toward the center of the bed. Dig holes and sink the corner posts Set the bottom boards in place and secure them to the posts. Repeat for the top boards if you are using 2. As you work, be sure you keep the boards level. If moles are a problem on your property, use chicken wire to line the bottom and extending a few inches up the sides of the box.

·         Spread the native soil to fill the bottom of the bed. Add organic matters such as compost and ground barks, a thin layer of garden lime and commercial planting mix (not potting soil) to fill the rest of the box. The soil will settle, so fill ‘er up. Mix the elements together and rake the bed smooth. Let it sit for a week before planting, if possible.

·         Good manners teach us not to walk on the bed we sleep in, and it’s the same in the garden. Put a stepping stone in the bed if you must, but don’t walk on the soil. Make pathways between beds wide enough to accommodate your needs. Some want a path wide enough for garden carts to traverse. Others prefer paths narrow enough to lay a board across the top of 2 beds to create a seat. You’ll avoid many weed problems by covering the paths with weed barrier cloth covered with organic mulch or gravel.

·         The discussion of what kinds of wood to use to build grow boxes for edibles centers on the safety of treated woods. Cedar, redwood and cypress, for example, last for years in contact with soil. No other treatment is necessary unless you want to retain their raw color. In that case, paint the boards with a sanding sealer or similar product. Other woods, like popular pine, must be sealed, painted or otherwise treated to resist rot. The chemicals used to treat woods to lengthen their useful life changed in 2004. Boards treated before then or of unknown origin may have been treated with arsenic, among other things. It’s the arsenic that can, in small amounts over several years, leech into soil and so would not be appropriate for edibles. Current technology uses less toxic chemicals with a smaller carbon footprint and boards should be clearly labeled as to their appropriate use. When in doubt about the age of recycled wood, its composition or previous treatment, slap a coat of few coats of latex paint on the boards and line the inside of the box with weed barrier cloth.



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