Until the early 2000s pressure-treated wood was typically treated with chromated copper arsenate CCA which is an extremely toxic chemical. Softwoods such as pine are easier to work with.
Safe Wood for Vegetable Gardens Hardwood.
Treated wood safe for vegetable gardening. Root crops such as beets turnips carrots and potatoes contained most of the metals they absorbed in the skin. Consider the use of reclaimed redwood which usually is available at specific construction material reuse. Heat treated refers to lumber that has been specially treated to kill pests and pathogens that may reside in wood.
If you have concerns about using ACQ-treated wood for raised beds paint or stain the wood use a heavy plastic liner between the wood and your soil or use a non-wood building material eg stones bricks. Sally Brown a research assistant professor of soils at the University of Washington knows her way around both food and metals. The closer vegetables are grown to the wood the more chemicals they absorb.
However I havent seen any research that suggests the level of the chemicals is significant enough to be of concern for human health. As a tree grows it. If using treated wood for raised beds plant vegetables 12 inches from the internal edge of the structure for added protection.
Avoid using older types of wood treatments such as CCA creosote and Penta-treated lumber. The process involves heating the wood to a core temperature of 56 C 133 F for at least 30 minutes. The safety of pressure treated lumber for raised bed gardens has been examined by several researchers.
Most newer treated lumber has removed CCA from the process and instead uses copper azole CA-B and alkaline copper quat ACQ. See Additional Resources below. Those massive reservoirs of cancer causing chemicals dont belong in any landscape.
The crops should be grown 10 inches away from CCA treated woods to prevent leaching of the chemicals into the plants. It doesnt require any chemical treatments. Should Pressure-Treated Lumber Be Used in a Vegetable Garden.
Some see no serious risk for humans in using them in a vegetable garden the amount of copper released being minimal and copper being considered essentially nontoxic unless present at extremely high levels. But there has been a lot of people worrying about whether treated wood is safe to use in the garden. Is It Safe to Use Treated Wood For Vegetable Gardens.
Soil experts disagree on using copper-treated wood products in a vegetable garden. Plants growing about six inches away from pressure-treated wood do not show even trace amounts of chemicals. Most wood is susceptible to damage from insects or microbiologicals threat throughout its life.
These days there are plenty of other materials in lieu of wood treated with suspect chemicals like arsenic to make raised vegetable gardens including Microshade treated wooden sleepers that are deemed safe for vegetable gardens and childrens play areas but are still pest resistant sustainable and reasonably priced. Heavy impermeable plastics can also be used to act as a barrier between the crops and the wood. This barrier will keep moisture and soil from the logs and will prevent any chemicals from leaching into the garden ground.
ORGANIC GARDENING campaigned heavily to make home owners aware of the dangers posed by old-school CCA chromium copper and arsenic treated wood back when I was the magazines Editor in the 1990s. Some commercially dyed wood mulches are made from recycled pallets and constructiondestruction site wood debris. But I also found out that pressure-treated wood produced more recently is probably perfectly safe to use.
Two main types of wood are available hardwood and softwood. Therefore peeling removes most of it. Arsenic is easily absorbed into the body but it does not exit the body nearly as easily.
Before 2006 the answer would have certainly been no. Studies have shown that arsenic from wood treated with CCA leaches into the soil and that copper although much less toxic leaches from ACQ and copper boron azole CBA a variant of CA-B. He stated in a bulletin titled Treated Wood in Raised Bed Gardening Scientific evidence and data have shown that using pressure treated wood for raised bed or box gardening is safe to adults and children in terms of the plants grown and used in these containers.
Even worse are old railroad ties and power poles. Best Alternatives To Pressure Treated Wood for Home Vegetable Garden One of the very best choices for your vegetable garden frames is local cedar. But now AQC is used and this is much safer for use in your vegetable garden.
From what Ive seen the consensus is that the chemicals do leach out of the wood into the soil and are uptaken by the plants in very small amounts. While less toxic than arsenic copper can still leach into your soil which has disqualified it for use in organic gardening. If the lumber surrounds a vegetable garden or fruit-growing area you can be completely sure youre safe by digging out the soil installing a layer of thick black plastic stapled to the lumber and replacing the soil.