Lumber is one of the top choices that people use for building raised beds.
However, there are many types of lumber you can choose, e.g. untreated and pressure-treated lumber are the most popular.
Ultimately, if your goal is to grow organically and reduce chemical exposure in your vegetable garden, some raised bed materials are better than others. And although it’s cheap and lasts longer than raw lumber, pressure-treated wood might not be the best choice for organic gardening.
You might be asking yourself: “Is pressure-treated wood safe for vegetable gardens?”
The short answer is that pressure-treated wood contains chemicals that, when the wood becomes wet, can leach into the soil of your raised bed. These chemicals ultimately work their way into the food that you’re growing. As a result, it’s probably best to avoid using pressure-treated lumber in vegetable gardens.
Is Pressure Treated Wood Safe for Gardens?
Generally speaking, organic vegetable gardeners agree that pressure-treated wood is not safe for raised bed gardens.
Pressure-treated wood is very different from untreated wood. Treated lumber is chemically primed to prevent decay and insects. Manufacturers make it by vacuum-sealing the wood and treating it with chemicals.
That’s why pressure-treated wood typically has a somewhat wet texture and its signature greenish color.
Constant exposure to the weather makes wood structures vulnerable to rot from moisture and insect attack. Therefore, pressure-treated wood is necessary for decks, railings, playground equipment, fences, non-edible flower beds, and other outdoor wooden structures.
However, the chemicals used to treat lumber – primarily copper – aren’t great in the vegetable garden. Although arsenic was the primary chemical used in pressure-treated lumber prior to 2004, copper still isn’t a viable option if you want to ensure your neat and clean vegetable garden stays chemical-free.
What Types of Wood Should You NOT USE in Vegetable Gardens?
Certain types of wood are not ideal for use in vegetable gardens. These types of wood either contain chemicals and are therefore harmful to plants or they break down too quickly.
Here are some types of wood to avoid in raised bed gardens:
- Pressure-Treated Woods: Pressure-treated lumber used to be a common choice for outdoor projects, including garden beds. But they’re now widely avoided due to concerns about the chemicals used in their treatment. These chemicals, which can include arsenic, copper, chromium, and other toxins, have the potential to leach into the soil and be taken up by plants.
- Railroad Ties: Railroad ties are often treated with creosote, a type of oil containing many chemicals, some of which are considered carcinogenic. These chemicals can potentially leach into your soil and can be harmful to both plants and people.
- Soft Woods: Woods like pine are not inherently harmful to gardens, but they break down and rot much more quickly than hardwoods. This can be a problem if you’re trying to build a long-lasting garden bed or structure.
- Certain Types of Hardwood: Black Walnut and Black Locust, for example, contain naturally occurring substances like juglone that are toxic to certain types of plants. These chemicals can leach into the soil and harm your vegetables.
- Wood Pallets: While recycling old wood pallets for garden use might seem like a good idea, it’s hard to know what kind of treatment the wood has undergone or what it has been used for. It might have been treated with harmful chemicals or used in the transportation of harmful substances.
The good news is, if you like the look of wooden raised beds, there are many safe building materials for your vegetable garden.
5 Types of Wood to Use for Raised Beds
Cedar is the safest type of wood to use in a raised bed garden. The reason is that cedar is naturally rot- and insect-resistant, and it can last significantly longer than other types of hard wood.
The only downside is cost. Cedar is much more expensive than softwoods like untreated pine. Here are some ideas for woods you can use safely in your raised bed garden:
- Cedar: Cedar is one of the most popular choices for raised bed vegetable gardens. It is naturally resistant to rot and insects, and it’s safe for use around food. Both Western Red Cedar and Eastern White Cedar are great choices.
- Redwood: Redwood is another excellent choice. It’s also naturally resistant to rot and insects, and it can last for many years. However, it’s generally more expensive than cedar, and it can be difficult to source, depending on your location.
- Cypress: Cypress is a rot-resistant wood that’s often used in gardens. However, it’s important to buy cypress that has been sustainably harvested, as some cypress forests are being over-harvested.
- Douglas Fir: Douglas Fir is more affordable than cedar, redwood, or cypress, but it also doesn’t last as long. The good news is that Douglas Fir is widely available, and it will typically last up to 5 years in the garden.
- Composite Boards: Composite boards contain a mix of wood fibers and recycled plastic. They are rot-resistant and require less maintenance than natural wood. But be sure the composite material doesn’t contain harmful chemicals.
5 Cheap Alternatives Materials for Building Raised Bed Gardens
When building raised beds or other structures where vegetables will come into direct contact with the wood, you should avoid using pressure-treated lumber. Instead, think of using cement blocks, cedar, redwood, hemlock, or plastic wood as alternatives.
Some of the cheapest and safest materials to build a raised bed with include:
- Cinder Blocks: Cinder blocks are super durable, and you can often find them for cheap, or even free if someone is getting rid of them. They are easy to stack and arrange in any shape you want. Plus, the holes in cinder blocks can also be used to plant herbs or flowers.
- Bricks:Bricks can be a fantastic material for raised garden beds. If you have any left over from a previous construction project, or you can find them at a recycling center or on a marketplace site, they can be quite inexpensive. They’re also extremely durable and will last a long time.
- Corrugated Metal: Corrugated metal sheets are a stylish and modern alternative to traditional wood. They’re highly durable and resistant to rot and pests. Depending on where you source your materials, they can be quite affordable.
- Bamboo:If you have access to bamboo, it can be a very inexpensive and sustainable option for a raised bed. Bamboo is naturally rot-resistant and very strong. It can be tied together to create a simple, lightweight, and portable frame. However, be aware that bamboo decomposes faster than wood like cedar or redwood.
- Cardboard or Thick Layers of Newspaper: Finally, another option is to skip the raised bed. Instead, cover the ground with cardboard, newspaper or grass mulch, a technique that’s like lasagna gardening or no dig gardening. While this doesn’t give you the tidy edges of a traditional raised bed, it can be a very inexpensive and efficient way to create a garden bed.
Is Pressure-Treated Wood Safe for a Compost Bin?
In the past, pressure-treated lumber was created using CCA (chromated copper arsenate). The arsenic was the true problem, not chromium and copper. Because of the arsenic and potential for leaching, pressure-treated wood is discouraged for use in compost bins.
Although arsenic really isn’t absorbed by plants, gardeners can be exposed to the chemicals by breathing in soil dust. Therefore, because composting is a powerful soil amendment, these chemicals can work their way into your garden soil.
In short, you should avoid using pressure-treated wood in composting.
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