Raised Bed Gardening

Katrina Edenfeld

If you live in an older home, you might wonder if it is safe to grow food in your yard. There could be lead in the soil from paint chips that have washed off the exterior of your home, or leaded gasoline may have contaminated the soil areas near streets. Even newer homes’ yards may be at risk if they were developed on former orchards or farmed land, for example. Lead arsenate was used for many years as a pesticide for fruit trees. If you plan to grow fruits or vegetables, or if children play in your yard, it is simple and advisable to order a soil test. (See the Lead in Your Soil article in the Gardening section for more details on soil testing).

Raised garden beds have many advantages: they extend the growing season by warming faster in the spring and staying warm longer in the fall, they drain faster than the surrounding soil in soggy weather, they contain plants to a manageable location, and they can allow gardening over soil that may be insufficiently fertile or contain contaminants.

Raised beds can consist of anything from piled soil or composting materials to constructed beds raised high for reduced-bending gardening. To begin raised bed gardening, consider the following:

Determine the size of your bed(s) and assemble the necessary materials. 4 — 8 ft. is a common size because it allows most people to reach all of the bed without walking in it. Bed height varies from a few inches to several feet; 27 in. is typical for wheelchair access. If your reach is reduced, or if you have specific space requirements, consider this while planning your garden. The World Health Organization recommends that raised beds over contaminated soil be constructed to a depth of 3 ft. with netting at the bottom of the bed to limit leaching of contaminants into the soil. Washington State University states that an impermeable barrier such as plastic or concrete is preferable if drainage can be provided. Container gardening is another solution to contaminated garden soil.

Consider a constructed border. Borders are commonly used to provide visual appeal and prevent erosion, with materials dictated by dimensions, budget, and aesthetic requirements. Pine is inexpensive and easily obtained, but will eventually rot where in contact with the ground. Cedar planks cost about four times as much, about $50 for a low 8 — 4 square foot bed; composite decking is another rot-resistant, but expensive, alternative. Pressure-treated or creosote-soaked wood should never be used; while they won’t rot with soil contact, they will leach contaminants into the soil. Raised beds can also be constructed from stone or brick; cost will depend on the height and material chosen. Kits for building raised beds are available from garden supply companies.

During garden bed construction, consider the materials and skills you may need. Planks can be connected by deck screws or metal brackets, with optional segments of 4 — 4 posts to strengthen the corners. A rock or brick bed of significant height will require mortar and skill. In uncontaminated soil, you may wish to dig out the area where the bed will go and construct it in place, several inches underground to block the roots of encroaching grass—among the most invasive plants likely to be in your yard. Some landscape-oriented companies sell raised bed kits or even raised beds.

A raised bed will need to be filled with soil. A home compost bin might generate sufficient soil to fill a single raised bed. County compost sites often have free-for-the-hauling compost and black dirt. The compost is generally made from grass clippings and leaves from the yards of local residents; while residents may use herbicides on their lawns, most herbicides permitted for home use will break down within months without composting, and somewhat faster in a compost file. Inquire about the source of black dirt and screening methods from a compost site or garden center; however, it may not be different from the soil in your own yard. Bagged gardening soil can be costly and often contains chemical fertilizers; read labels carefully.

While it may seem like a tall order, raised garden beds really can do it all. Plants produce better, even when planted more densely, because they grow in deep, loose, fertile soil that is never walked on. Raised beds save time and money because you need only dig, fertilize, and water the beds, ignoring the soil in the paths. Weeding needs are also reduced because closely-spaced crops exclude sunlight and water from weed seeds. Fill your raised bed and start planting!

Read Up

Square Foot Gardening: A New Way to Garden in Less Space with Less Work by Mel Bartholomew. Rodale Books 2005.

Act Locally

Twin Cities Metro Area Compost Sites, rethinkrecycling.com

Simple Living Gardening Tips

Excerpted from Mother Earth News, Aug./Sept. 2009

Use an old saltshaker to plant tiny seeds.

Scatter dog hair in your garden to repel critters.

Extend the life of your squash by dipping the stems in melted beeswax or paraffin wax.

Keep onions for up to a year by storing them in old, clean pantyhose. Hang them in a cool, dry place and cut off below the knot to retrieve an onion.

Raised Bed Gardening

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