A few months back, Popular Mechanics Magazine ran an article about their partnership withRebuilding TogetherPhiladelphia. In June of 2010, they worked with local volunteers (aspart of a wider series of repair and rebuilding projects) to build a series ofraised gardens so the local folk could grow some of their own produce (see photobelow).
What struck me is the use of pressure treated wood for the gardens! Ihave been pelted with questions for years concerning the safety of usingpressure treated wood for vegetable gardens. Though I had feelings on thesubject (and have built dozens of them for friends and clients) it was onlyrecently that I felt there was enough information to make a firm recommendationon this website.
Yes, the "new" pressure treated wood is safe for use forraised garden frames... with a few precautions!
Up until 2003, the most common preservative used for pressure treated woodwas chromated copper arsenate (CCA), a compound using arsenicas its primary rot protectant. Over years, the industry, in cooperationwith government recommendations, phased out the use of CCA for all residentialand most commercial wood pressure treatment. Part of the reason was thefear that the arsenic would poison the soil and anyone who touched it.Though actual cases of poisoning via pressuretreated wood use by the public were hard to find, there wasenough circ*mstantial evidence of soil contamination to warrant a change.
New preservatives with either copper or chromiumas the primary preservative replaced CCA, and that changed the safety dynamicdramatically. Unlike arsenic, which is well absorbed into and retained bythe body (explaining its toxicity even in long-term, small exposures), these newproducts (though toxic in large amounts) are not absorbed efficiently by thebody so the miniscule exposures from touching or working with these products aresafe provided simple exposure precautions are taken, such as handwashing and collection of the sawdust.
Do plants absorb the preservative in pressure treated wood raised garden frames?
Yes, plants can absorb these preservatives, but tests have shown that theamount of preservative leached from the newer PT wood products is so low that itis virtually undetectable. According to my reading, the primary toxicityconcern raised so far in the effect of the new preservatives on lower plant lifesuch as algae, which wouldn't affect most homeowners unless you have a lakenearby.
Applying a sealer can protect against CCA exposure...
According to the EPA, studies show that the application of apenetrating oil finish can reduce or eliminate exposure to CCA in older decksand to the preservatives used in newer decks. So it is recommended that allpressure-treated surfaces that have human contact be coated with an oil finishas needed. It has been noted in some studies that paints and opaqueexterior stains do not offer the protection of stains that are absorbed moredeeply into the wood. They should be recoated at least every few years orwhen water no longer beads on the wood surface.
Some manufacturers are adding a water repellent to the preservative, whichwould make the need for a sealer less important or unnecessary for garden framesand rough structures, though for decks subject to abrasion and sun exposureregular sealing is still a good idea to preserve the surface.
How applicable or even necessary this is for a raised garden frame I'll leaveto your judgment.
Tips for working with pressure-treated wood...
- Predrill any nail or screw holes within an inch of the end of the board.This lessens the chance of splitting the board while fastening it. Even if it doesn't split when you initially fasten it down without predrilling, it will very likely do so later as the wood dries out. BE SURE TO CLEAN UP ALL SAWDUST!
- Use the right fasteners.Use only screws or nails that are galvanized and designed for use with the newer copper-based pressure-treated wood.
- Be sure you are purchasing the correct grade of PT wood for your project. The newer PT wood products are more expensive so there are more gradesavailable to keep the cost down. You must use ground-contact grade forraised gardens if you want them to last the "test of time".
So here we are!!
Obviously, there will be more information on this topic and I will keep ontop of any changes or new studies that might help you make the best decision.Best of luck with your project!!
FAQs
Concerns stemmed from older treatments containing arsenic, a toxic chemical. However, the good news is that modern pressure-treated wood utilizes copper-based preservatives, making it perfectly safe for cultivating delicious and healthy vegetables, herbs, and flowers.
Is it okay to use pressure-treated wood for garden beds? ›
It's less prone to warping, twisting, or cracking compared to other wood types, ensuring your garden beds maintain their structural integrity over time. These compelling benefits make pressure-treated wood an excellent choice for constructing garden beds.
How long does pressure-treated wood leach chemicals? ›
The treated wood can leach toxic chemicals for many years, so it would be wise to assume that the wood remains toxic. That said, there are a number of strategies you can use to minimize exposure of your raised veggie garden to the treated wood, as noted below.
Should I use pressure-treated wood for framing? ›
Key Takeaway: When it comes to lifespan and durability, treated wood outlasts untreated when exposed to the elements. If your project is indoors, and moisture isn't an issue, untreated wood can last forever.
Where not to use pressure-treated wood? ›
Don't use pressure-treated wood for food containers or cutting boards. Even playsets should get a protective sealant. Be careful when working with pressure-treated wood. Cover up skin with gloves and protective clothing.
Is Lowes pressure treated wood safe for vegetable gardens? ›
Safe practices for working with treated wood recommend treated wood not be used where it may come into direct or indirect contact with drinking water or a component of food, animal feed or beehives. The USDA prohibits treated lumber for soil contact use in their certified National Organic Program published in 2011.
What wood should not be used in a raised garden bed? ›
Avoid using older types of wood treatments such as CCA, creosote, and Penta-treated lumber. Research from Oregon State University showed that pressure-treated lumber does increase soil copper concentrations by a minor amount, but only within 1 inch of the raised-bed edge.
Is pressure treated wood still toxic? ›
The amount of leached chemicals generally drops quickly within a short distance from where soil is in contact with the treated wood. If you follow safety precautions around treated wood, you should not have any health effects as a result. However, you should avoid exposure to the smoke or ash from burning treated wood.
How to prevent pressure treated wood from leaching? ›
For existing CCA-treated structures, the best way to minimize arsenic leaching is to seal the wood by apply- ing a sealant every two years. This practice is in accordance with the wood manufacturer's recommendations for maintenance of CCA-treated wood.
When did they stop using arsenic in pressure treated wood? ›
The U.S. Environmental Protection Agency (EPA) and the lumber industry agreed to stop using CCA-treated wood in residential settings starting in 2004. This included playground equipment, decks, picnic tables, landscaping, fences, patios, and walkways.
The simple answer is yes, pressure-treated lumber can be used in any interior application except cutting boards and countertops.
What is better than pressure-treated wood? ›
Cedar's natural resistance to rot and pests, coupled with its natural beauty and ease of workability, far outweighs the benefits of pressure-treated wood.
What can I use instead of pressure treated framing? ›
Alternatives to treated wood are being used more frequently. Examples of alternatives to treated wood are native decay-resistant woods, exotic decay-resistant woods, composite woods (plastic woods), vinyl, and rubber (figure 4). Only the heartwood of decay-resistant species is durable.
Is treated wood safe for vegetable gardens? ›
Pressure-treated lumber is not recommended for raised beds for growing vegetables. Never use railway ties treated with creosote.
What destroys pressure treated wood? ›
Rot is a Real Threat for Any Wood
Pressure-treating can make wood water-resistant, but it's not 100 percent rot-resistant. Any time the wood moves, bends, or cracks, water can enter. While this may seem worrisome, the key is to keep the water away.
What eats pressure treated wood? ›
Any wood, pressure treated or not, that is directly in contact with soil will likely rot eventually and become susceptible to termite and carpenter ant attacks. Take wood destroying insect precautions along with following up with a professional pest control services.
Is pressure-treated wood toxic to plants? ›
Studies have definitely shown some leaching of ingredients from this wood into garden soil and onto foliage (most likely from dust kicked up from the soil), relatively little in plants themselves (many of the most concerning elements aren't easily taken up by plants), and very low concentrations in any event.
Is pressure treated wood safe for bed frame? ›
The simple answer is yes, pressure-treated lumber can be used in any interior application except cutting boards and countertops.
What is the best wood to use for raised garden beds? ›
Cedar is often considered the golden standard for building raised beds, and it's my favorite option. It's naturally resistant to rot and pests thanks to its natural tannins. (Pine, by the way, has a lower level of these tannins, so it's not naturally protected from rot and pests.)
Is pressure treated wood safe for outdoor use? ›
Using pressure-treated wood for projects like wooden decks and fences will keep your outdoor structures beautiful for years by resisting termites, rot and fungal decay.
