Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden. More on Tony O’Neill
Wood is a versatile material for a vegetable garden, regardless of whether it is used to make raised beds, path edges, or even framing for pergolas, fruit cages, or animal enclosures. But many people have been worrying about whether treated wood is safe to use in the garden.
Is It Safe to Use Treated Wood For Vegetable Gardens? Before 2006 the answer would have certainly been no. But now AQC is used, which is much safer for your vegetable garden.
The challenge is that all the common ways to conserve wood face challenges when growing edible products. For many of us, one of the main benefits of growing our food is knowing that our vegetables have not been artificially sprayed, processed, or improved.
Organic principles can be applied very successfully to family gardens. Still, treating woods that come into contact with soil and plants can cause many questionable chemicals to leak into the soil, polluting crops. It is difficult to find details about the scope of this problem, but the following treatments are commonly questioned:
There is a long debate in organic gardening: Can pressure-treated wood be part of an organic garden? This is what I know. Wood not treated with pressure tends to rot quickly when touching the ground.
Pressure-treated wood until 2006
Weight-treated wood sold in the USA. Canada and Europe used to contain chromium copper arsenate (CCA). Over the long haul, this item discharges arsenic to the dirt under specific conditions more than others.
The dread was that arsenic could be consumed by vegetables and other palatable plants and moved to people. And everybody realizes that arsenic is poisonous. Moreover, consuming wood containing arsenic is riskier than utilizing it in the nursery.
In North America and much of Europe, CCA-treated wood has been removed from the residential timber market but still allowed to be used in some commercial applications sometime in early 2003. The UK banned using CCA in early 2004 in Canada and the USA in 2006 in Australia.
Pressure-treated wood after 2006
Since then, two other copper-containing products have been widely used in pressure-treated wood: alkaline copper (ACQ) and copper azole (CBA).
These products no longer contain arsenic. Instead, copper is used, which helps in protecting the wood. Copper has no health concerns and is relatively harmless to the environment. ACQ is a water-based solution that uses ammonia to penetrate the timbers. But copper is the active ingredient in an insecticide and fungicides.
In any case, copper is considerably less poisonous than arsenic. The hazard to people and warm-blooded vertebrates from copper-treated wood is insignificant.
However, fish and bugs are delicate, and copper-treated wood should never be utilized in lakes or streams. Soil specialists agree: they see no peril to people when using copper-treated wood items in a garden.
The measure of copper discharged is minimal, and copper is considered non-poisonous except if it is available at extremely high and elevated levels. Be that as it may, original item confirmation offices don’t permit the utilization of copper-offered wood to produce confirmed organic vegetables.
Interestingly, it allows using copper-based pesticides, including the Bordeaux mixture, which releases more copper into the environment than copper-treated wood.
Pressure Treated Wood “tanalized.”
This is where the wood is preserved before purchase by subjecting it to chemical treatments under pressure to absorb as much wood as possible. Most fences and posts are handled this way to extend the life of the cheapest softwoods used to make them.
The problem is that obtaining information about the chemical mixture used in the process is generally difficult, especially since wood may have been treated with pressure before arriving at the place where it was purchased for a long time.
There were serious concerns about using arsenic (CCA) compounds and heavy metals, especially when they become contaminated or enter the food chain.
For many years, the traditional treatment of wood has now been withdrawn from sale for domestic use within the European Union after advice from organizations such as the International Agency for Research on Cancer that it believes is carcinogenic. Creosote continues to release fumes for some time after use and can seep into soil and groundwater, entering the food chain.
It enters well into the wood, gives further security than numerous other covered additives, and is the reason for some wood stains. Some of them rely on vegetable oil.
Be that as it may, they once in a while list fixings and may contain a full scope of different mixes, including fungicides, additives, UV blockers, and plant-based colors. Accordingly, it isn’t clear whether using it in natural cultivating territories is alright.
Some painted wood treatments.
Acypetacs such as Cuprinol are safer than previous treatments. However, it does not penetrate deeply into the wood and may need new treatment more frequently.
Of course, you cannot quickly treat it when you have standing ground against a wooden deck. Most products claim to work for years, but this is for fences or gates that can dry out and not for those exposed to moist soil.
Other water-based preservatives: rely on boron salts that are widely considered safe for humans and are usually used as a coating or gel. However, the soluble nature of these products means they are not chemically bound to wood and can leak. It is also difficult to find in stores and takes a long time to dry.
The traditional wood treatment made from natural flaxseed oil has excellent preservative and water resistance properties. However, drying is prolonged, and applying it in cold or humid climates may not be useful because it can Stay sticky for weeks.
As a result, many available flaxseed oils are not pure raw flaxseed oils but rather a mixture of solvents such as mineral spirits, often called “heated flaxseed oils,” to speed up the drying process, making them less natural. Worse, other flax oils contain many “fats,” like heavy metals used in pressure-treated wood.
Therefore, you should know what to buy and remember that, as a natural material, it does not protect the wood from sunlight, UVA, or mildew. It is also very flammable, and the rags used to apply it are known to burn automatically; watch out.
Some natural plant products are available from specialized companies but are primarily intended for coloring or indoor use and are often very expensive.
An elective technique is to pick hardwoods that, dissimilar to common softwoods, for example, pine, will last longer without treatment, as long as 20 years; however, confirm that they are from affirmed ranger service sources (FSC) there is condition.
Consider the degree to which they were moved, alongside a lot greater expense. The best option is reused plastic boards, which are sturdy and accessible from organizations like Link-a-Board (or Gardener’s Supply Company in the United States).
Plastics are not viewed as naturally well disposed of; however, this organization reuses PVC from windows and entryways that should not be burned or sent to landfills.
Since the boards contain an air hole, they are acceptable encasings for the dirt, encouraging them to heat up more rapidly in the spring and keeping plant roots at a uniform temperature. The expense is relied upon to be higher than the wood cost, yet its worth is acceptable if its term is considered.
After considering all these options, the only wood treatments that fit my organic principles seemed to include natural products that would almost double the wood cost required for my raised beds! Next, I made the surprising decision that it was better to use untreated wood, thicker (2-inch) structural rating panels attached with galvanized surface screws.
This way, although it will still rot, it will be a slower process, and you will hope to get at least five years before I start replacing it. An older hardener was not convinced. He assured me that the only permanent way to treat wood is a mixture of engine oil from the sump of an old car!
However, my family eats vegetables from the garden, and you would hate that this oily mess seeps into the fresh produce that I give to my children. Ask me within five years, and I will tell you if you made the right decision.
Wood treatment is intended to prevent natural degradation. Most woods do not last long in a humid environment and outdoors, so designers often look for wood treated with pesticides that prevent fungi and insects from breaking down wood fibers.
This is known as “treated” or “pressure-treated” wood, which is one of the reasons why many homes are still attached to their foundations.
Based on wood treatment, growing food in beds made of treated wood is unsafe as safety has not been established. Get away from treated wood in the garden, including railway sleepers, as the ones available may have been soaked in creosote, and you don’t even want to know what’s in it.
ACQ Wood Treatment
Don’t worry; ACQ copper-based solutions have little to no effect on the garden. Plus, there are many other options available. You can use traditional wood and accept that you must replace it within 5-8 years.
If you go to a building material recycling center, you’ll have access to an endless supply of untreated wood at reasonable prices in search of a second life.
Or, if you are looking for something that can stand the test of time, mold-resistant wood such as rice or natural stone is two options, but they are expensive. Still, they may be costly unless you can collect stones near your home or find rice which can be tough; it is not the most environmentally friendly way.
Often, people think they need to build a raised bed, while in reality, while sometimes cultivation directly in the ground will work well. But if gardening directly on the ground isn’t an option, consider using brick or blocks to form your raised beds. Wooden untreated logs would last a long time too.
This will give you about 10 inches of height that you can fill with dirt if you need it. It may look like it won’t last, but if they break down, they will nourish your soil too.
What to do
So, should one use copper-treated wood in a grove with raised beds? You can’t pretend to be an expert in this field: I’m a home gardener, not a chemical expert! But I think there is enough information to decide.
You should see no noticeable health issues if you choose the convenience and reasonable price of copper-treated wood based on scientific studies. Or will you remain using untreated wood? It’s less expensive, but that means replacing it every 7 to 10 years. Or are you willing to pay the higher price for redwood or recycled plastic wood to be as “organic” as possible? This is your decision.
Some other possibilities
Use Low-cost softwood and paint with a wood preserver. It will help it last longer, but some organic gardens may object.
Unfortunately, some of these products are acceptable in organic gardening, at least not if you grow vegetables commercially and hope to get your organic certification one day.
Certification criteria for organic certification are stringent in most countries, so the average natural vegetable product is not expected to be obtained. However, untreated wood can be coated with flax oil. This treatment will help resist water, and flaxseed oil is one of the few insulation products 100% accepted in organic gardening circles.
Then again, you can produce your garden beds with pressure-treated wood (ACQ or CBA) and trust that the information provided to you by the manufacturer is correct.
Me, I see no problems using ACQ-treated timbers in my garden. I am an organic gardener and have never had a lab test showing increased copper in my soils. So to date, this has not caused an issue.