Treated wood is intended to be moisture and rot resistant, which makes it seem like a good choice for garden stakes that are exposed to daily watering and outdoor elements. Although treated wood has benefits for building applications, the chemicals that give the wood its durability pose potential risks to your garden and your health.
Although low levels of arsenic naturally exist in soil and water, pressure-treated lumber contains additional arsenic, which can leech into surrounding soil. Arsenic does not move much when it enters soil, so if plants are growing near treated wood stakes, there is potential that it can enter their nearby root systems. While this may not harm the plant, it can be poisonous to humans. The Massachusetts Department of Environmental Protection website recommends removing peels before consuming any root vegetables grown near pressure treated wood. The levels of arsenic that enter vegetables from treated wood are negligible, but continued exposure could result in acute poisoning.
The chemical compound used in older pressure-treated wood is chromated copper arsenate (CCA), which has been linked to cancer. While CCA-treated lumber has been outlawed, old supplies of this product may be present in your wood shop or garden. Recognise this treated wood by its green tint on cut ends. When working with CCA-treated wood, always wear gloves and a dust mask. If you expect to be touching the treated wood stakes when working in your garden, use a oil-based sealant to cover the stakes and prevent transfer of chemicals to your skin.
Organic Gardening Problems
Pressure-treated wood should not be used as stakes in organic gardening. Due to the chemicals inherent in treated wood, it can harm your organic gardening program. Aside from potential for soil contamination, these chemicals can deter beneficial insects. The chemical additions to pressure treated lumber are pesticides, intended to stop termite damage in building applications. Unfortunately, these chemicals are hazardous to animals and insects, including those who are helpful to your garden. Contact with treated wood stakes may convince your organic pest control partners (beneficial animal and insects) to look for food elsewhere.
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- Gardens Alive: The New Treated Woods - Safe for Garden Use?
- Fine Gardening: Does Pressure-Treated Wood Belong in Your Garden?
- Massachusetts Department of Environmental Protection: Pressure Treated Wood - Questions & Answers
- CBS News: Dangers of Pressure Treated Wood
- Ecology Center: Pressure Treated Wood