Growing Food at Home

Growing Food at Home

What materials should I use for building raised beds?

When building a raised bed, look for rot-resistant natural wood, like juniper, cedar, or redwood. If you’d like to use another type of wood, you can paint it with milk paint to protect it from weather or plan on replacing it in few years. Do not use treated wood, which contains chemical preservatives that may leach into your soil. To learn more about the hazards of treated wood and safer alternatives, please read our fact sheet Paints, Solvents, and Wood Preservatives. 

You can also build raised beds with natural stone, brick, concrete blocks, or recycled sidewalk pieces. Lumber made of recycled plastic is another option; choose products made of HDPE or LDPE (the most common ingredients) and avoid those that contain polystyrene or PVC.

I'm reusing an old raised bed and I think the wood is treated. What should I do?

The simplest solution is to reserve beds made of treated wood for ornamental plants and to create new beds for food plants (see above for healthy materials to use). If you don’t have room to create a new bed, you can rebuild the old bed using healthy materials and new soil (see our FAQ on soil below). Dispose of the treated wood at a hazardous waste collection site (visit this page for disposal information), and move the old soil to another part of your garden where it will not be disturbed, especially by children.

If you are not able to replace the treated wood and don’t have another spot to garden in, consider growing plants in containers, using fresh soil. Even if you put fresh soil into your raised bed, the treated wood may leach harmful chemicals into the soil. CCA-treated wood, which has staple-like indentations, may leach arsenic. It is possible to test the soil to monitor the arsenic levels, but if you do find that high levels have accumulated, you may have to forfeit your plants.

For tips on growing food plants in containers, contact the Garden Hotline at (206) 633-0224 or help@gardenhotline.org.

FAQs on related topics include: Testing Garden Soil for Lead and Arsenic, and My deck may be made of treated wood. What should I do?

How can I stop weeds from coming up without using chemicals?

To block weed growth between vegetable rows, try laying down mulch (like wood chips or straw), burlap bags, cardboard, or old clothes. You can also try plastic landscaping  fabrics, which help to keep some weeds from pushing up. These plastic fabrics are made of less-toxic plastics and are not likely to leach toxic chemicals into your soil. Avoid reusing old carpet, which may contain toxic ingredients like PVC plastic (vinyl), toxic flame retardants (PBDEs), or stain-resistance chemicals (PFCs).

Cardboard sheets can also be used under gravel or stone pathways to prevent weeds from coming up.

What kind of soil do I need?

Healthy soil is the foundation of a thriving garden. Use soil from the area surrounding the raised beds, and mix in compost.  If you need to purchase soil, look for an organic product like Cedar Grove’s Vegetable Garden Mix (www.cedar-grove.com/products.asp).

Compost increases soil’s ability to retain moisture, attracts earthworms and beneficial microorganisms, and slowly releases nutrients. It can also be used as a mulch. How much compost should you add? King County offers these guidelines for a 100 square-foot garden area:

• Clay soils – 16 cubic feet = 2-inch layer of compost
• Sandy soils – 24 cubic feet = 4-inch layer of compost

Mix in the compost to a depth of 10 to 12 inches. “Clay” and “sandy” refer to your soil texture. Clay particles are the smallest, sand particles are the largest, and silt particles are in between. If you’re lucky, your soil may contain a balance of all three (called a loam). If you don’t know what your soil texture is, you can send a sample to a soil testing lab (see our FAQ below) or try this simple squeeze test: put one or two tablespoons into your hand, and add water, and knead. If you are able to form the wet soil into a ball and it forms a ribbon at least an inch long when pressed between two fingers, your soil is clay. If the wet soil doesn’t easily form a ball or ribbon, it is sandy. If you can form a ball but only a short ribbon between your fingers (about ½ inch), you have a loamy soil.

You can also make your own compost from food and yard waste! To learn more, see Seattle Public Utilities’ brochure “Composting Food and Yard Waste At Home.” (http://www.seattle.gov/util/stellent/groups/public/@spu/@csb/documents/webcontent/spu01_001989.pdf)

Where can I get my soil tested?

If you’re worried about possible toxic contamination of your soil and would like to have it tested, you can send your soil to a lab for testing. The U Mass Soil Testing Laboratory (www.umass.edu/plsoils/soiltest/) offers a standard soil test for home gardeners including pH, nutrients, and extractable metals for only $9. Agricultural and environmental labs that offer soil testing include:

• Cascade Analytical, Inc., cascadeanalytical.com, (800) 545-4206
• Columbia Analytical Service, Inc., caslab.com, (800) 695-7222 (menu choice 7)                
• KUO Testing Labs, kuotesting.com, (509) 488-0112

Contact the lab to determine the proper sampling procedure, and don’t hesitate to ask them for help interpreting the results. Keep in mind that low levels of heavy metals are common in most soils. For tips on testing soil for lead and arsenic, please see our FAQ Lead and arsenic in garden soil. For guidelines on reducing exposure to arsenic in garden soil, see our FAQ My deck may be made of treated wood. What should I do?.

What can I use for fertilizer?

If you find that your soil needs extra nutrients, look for organic fertilizers like Walt’s Organic Fertilizer and Soil Amendments (www.waltsorganic.com). Whitney Farms also offers a line of organic fertilizers and soil amendments. Avoid fertilizers labeled as water-soluble or quick-release, which are more likely to run off and pollute surface or ground water. Organic and coated fertilizers release nutrients more slowly and are less likely to cause water pollution.

For a list of fertilizers and soil amendments ranked by solubility and nutrient composition, please see Grow Smart, Grow Safe, a consumer guide to lawn and garden products. For additional tips on choosing fertilizers, please read our fact sheet Choosing Fertilizers for the Lawn and Garden.

Adding compost will generally reduce your need for fertilizers. Compost tea, a concentrated liquid that can be purchased at local garden stores or made at home, can build soil microorganisms while protecting plants from mold and blight. Chinook Compost Tea (www.chinookcomposttea.com) will apply compost tea to your entire yard.  

Another natural additive that will build your soil and reduce your weed pressure is worm tea, a solution of worm droppings which is rich in the nutrients plants need. You can purchase worm tea concentrate from Wiser Worm Farm in Olympia (www.wiserwormfarm.com) or Sequim Prairie Star Enterprises at several Washington farmers markets. Follow the directions on the bottle to properly dilute the concentrate, then apply to soil or leaves.

What sort of hose should I use?

Beware hoses with the label “Do not drink from this hose. Wash hands after use.” These hoses are probably made with vinyl or PVC, and the nozzle or hose may contain lead.

Instead, look for hoses made out of polyurethane or rubber labeled “Safe for Drinking.” Some examples include Apex Never Kink Hoses, Water FlexEEL Garden Hose, and Gatorhyde Green Garden Hose. Be sure that the rubber hose you choose is not a rubber-vinyl mix. Some hoses contain polyethylene (LDPE or HDPE) or reinforcing materials like nylon and polyester; these are all less-toxic materials and are fine to use.

What’s a safe way to keep young plants warm?

Avoid using PVC or vinyl in your fruit or vegetable garden.  (Link to Vinyl Fact Sheet) To keep plants warm in cool seasons, consider building a cold frame using old windows or glass doors. A glass greenhouse is ideal, but the price can be prohibitive. Building a cold frame can be as simple as laying a glass window or door over the top of a raised bed (leave plenty of room for plants). To keep plants warm against a wall, you can lean a glass door or window against the wall at an angle.

If using a re-purposed older glass window or door, make sure the surrounding wood or material is not painted with lead paint. You can send a paint chip to a lab to find out if it contains lead. Testing labs include Amtest (amtestlab.com), CCI Analytical Labs (ccilabs.com), Laucks Testing Labs, (lauckslabs.com), and NVL Labs (nvllabs.com).

How can I control slugs, snails, and insects without pesticides?

Plant a variety of species, and take note of what does well, and what is bothered by pests. Consider hand-picking large pests (like slugs and snails) or infected plants to remove the pest from your garden. Attract and protect birds and beneficial insects in your yard. Introduce biological controls, like carnivorous insects, who will eat pests. Examples include lacewings and parasitic wasps.

Creating a barrier with a sharp material, like eggshells, can help deter slugs. You can also try putting out a pie plate with beer, which will attract and drown the slugs. Some gardeners growing plants in pots or raised beds use copper strips (at least four inches wide), which slugs don’t like to cross over.

For guidelines on controlling specific garden pests, please see our FAQ section: Lawn and Garden Pests.

What over-the-counter pest controls can I use in my fruit and vegetable garden?

In the fruit or vegetable garden, be particularly cautious when purchasing any sort of commercial pest controls. Using insect or rodent traps is a good way to address pest issues without applying any sprays or dusts. If you need to purchase a topical pest control, remember that spot application only where needed is always safer than widespread application of a product.

For caterpillars, you can purchase ingredients which contain Bacillus thuringiensis (B.t.), a natural bacterial toxin. Safer makes several products to control ants and crawling insects. For a full, up-to-date toxicity rating of pest control products, download a copy of WTC & King County’s “Grow Smart, Grow Safe” booklet at www.govlink.org/hazwaste/publications/growSmart2006web.pdf.

Also, keep in mind that healthy plants are more resistant to attack from insects and diseases. Be sure to support your plants’ healthy growth by creating and maintaining healthy soil, providing the appropriate amount of light, and watering and fertilizing properly. Rotating the locations of your plants each year can also help to reduce pest populations, and some varieties of food plants are more pest-resistant than others.

Further Resources:

Garden’s Alive: www.gardensalive.com

Garden’s Alive offers a wide variety of organic and biological pest controls and gardening supplies.

Seattle Tilth Garden Hotline: www.gardenhotline.org

Hotline staff answer phone calls and emails six days a week, and have organic answers for common (and not-so-common) northwest gardening questions. Call (206) 633-0224 or email help@gardenhotline.org.

Northwest Coalition for Alternatives to Pesticides:  www.pesticide.org

Offers non-pesticide solutions for preventing and controlling pests.