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It is easy to see the appeal of raised bed gardens. Raised bed gardens can be used to create fertile spaces in the garden for those with limited mobility, poor soil or small yards. They can also be customized to fit the needs of gardeners.
You might be interested in creating your own raised garden beds if you have the tools and the necessary skills.
These are the 7 best wood options for raised beds
Pressure-treated (Yes, really)
Cedar
Cypress
Black Locust
Pine
Oak
Redwood
There are some things to consider when using these woods. We will discuss them, but the most important aspects of building raised beds are cost, availability, durability. You have other options, including wood alternatives. We will also discuss the three main types of wood we should avoid. Let’s get down to the controversial wood option on our list.
Pressure Treated Wood
Can pressure-treated wood be used for raising beds? Yes. Yes, it is possible to find pressure-treated lumber safe enough for use in a vegetable garden. This may be an option that you should consider depending on your budget and growth zone.
Pressure-treating lumber has the purpose of making it more resistant to decay and rot. Chemical treatments are applied to wood to repel insects and fungi. Depending on the wood type, untreated wood begins to decay within one year.
Preservatives such as micronized copper azide (CA) or alkaline copper quanary ammonium (ACQ), have been the most popular treatments for residential lumber since the end of CCA. These compounds can be used in vegetable gardens.
This warning is important. However, if the chemical treatments were applied cosmetically to the wood’s surface it shouldn’t be used for “ground touch.” This means that it is unsafe to come into direct contact with the soil.
Wood that has been pressure-treated (the preserving chemicals are evenly distributed throughout the wood) will have a label that indicates that it is safe to be used for ground contact. Reputable building supply stores can provide Safety Data Sheets which give more information about the chemicals.
The availability of pressure-treated wood is great, it’s durable, more affordable than other hardier options, and it’s also widely available. These are the steps to follow if you want to plant a garden using pressure-treated lumber.
Regularly test your soil for heavy metals. Take out any vegetables if you find heavy metals in your soil and plant flowers. You can also replace the soil and then plant vegetables.
To prevent soil and wood from coming into direct contact, line your garden beds with plastic sheeting. This will not affect the quality of your garden’s overall appearance, as long as drainage holes are allowed.
Please note that pressure-treated wood cannot be accepted by organic growers according to the USDA Organic guidelines (source).
This video by Gardener Scott explains the facts and myths surrounding pressure-treated wood.
Alternatives to Pressure Treated wood
You can build a raised garden using a variety untreated woods if you don’t want to use pressure-treated wood. These are some of the things to consider when deciding which garden is right for you.
Cost
Available
Durability
Resistance to decay and rot
Cedar
Cedar is a popular choice for raised garden. Cedar is a great choice, whether you are building your own or buying a kit.
Cedar is the “gold standard” in raised beds due to its resistance against insects and rot. Cedar is long-lasting even if it is not treated.
This Cedar Raised Garden Bed Kit is a great example (link to Amazon).
The most common variety to be found at a lumber store is West coast cedar (Thuja pilata). Although it is more resistant to rot than the western red cedar (Juniperus Virginiana), it is more difficult and more costly to find.
Cedar’s main drawback is its high price. Although cedar may seem expensive, it is worth the investment. Source
Cypress
If you live in an area with cypress trees, you might be able find Cypress (Taxodium diistichum).
Although it doesn’t last as long as cedar or pine, Cypress is much more resistant to decay and rot than other woods. If you are looking for a raised garden kit, it is strong, attractive, and simple to find.
It may be difficult to find raised beds if you are looking to make your own. Although cypress is often recommended for raising beds, it isn’t widely available. For example, gardeners living in the southeastern United States will have a better chance of finding it than those who live elsewhere.
You may be able order cypress lumber through your local retailer if you wish to use it in your raised beds. However, this is likely to be very expensive.
Black Locust
Because of its resistance against rot and decay, black locust wood makes a great choice. Because it is resistant to rot and decay, black locust wood is increasingly being used for outdoor projects such as decks and fences.
Black locust has a major problem: it is not readily available. It is considered an invasive species in some states, which restricts the sale and propagation. This means that black locust lumber may be difficult to find depending on where you live. Also, high demand can lead to higher prices.
Ask your Extension agent for information about black locust lumber availability in your area. It is possible to find it and it is a great candidate for your raised beds (source).
Pine
Pine is the most common wood and the least expensive. Pine is strong and simple to use which makes it an attractive choice for a wide range of building projects including raised beds.
Pine isn’t very resistant to insects, rot, and decay. Pine beds are often replaced within five to six years by gardeners.
Pine may be an option for those with a limited budget, who are not experienced builders, or who simply don’t mind having a temporary raised bed.
Other Hardwoods
You might use oak or redwood depending on where you live and what materials are available.
It is possible to spend a lot of money on a raised bed made from durable wood.
These woods are a little more resistant to rot than pine and look quite nice. Even if you’re willing to spend the money, it may not be available in sufficient quantities (source).
Natural wood preservers
There are natural preservatives that can be used to prolong the life of untreated wood. Although their results may vary, they won’t provide the same protection as ACQ.
Raw Linseed Oil
A flaxseed oil extract called raw linseed oils, which is a cheap way to protect wood from certain types of decay, is also inexpensive. It acts as a sealant to keep moisture from porous surfaces. It can also repel fungi, and other microorganisms.
Tung Oil
Tung oil, which is extracted from the tung tree seed, can also be used as a moisture-repellent preserver. It is usually more expensive than linseed oil, and it is often combined with chemicals that aren’t safe for gardening. To avoid these problems, be cautious when buying tung oil.
There are other options
Plastic, metal and masonry are options for those who don’t like pressure-treated wood but still want something that lasts longer than untreated wood.
Plastic
Plastic doesn’t last forever but sturdy plastic planter boxes and plastic barrels will hold their value over time. Even small swimming pools can make good raised beds if they have drainage holes.
Metal
Barrels are often cut in half, as well as aluminum and steel planters, discarded cattle trots, sheet metal and other metal containers.
Galvanized metal and chemicals containing metals, such as zinc, can leach into the soil. It is also important to verify the origin of any materials you purchase before planting anything edible. You should ensure that you only purchase sheet metal and metal containers from a reliable source. They can answer any safety concerns you might have (source).
Masonry
Cement blocks, bricks, native stone and brick are the most durable and expensive materials for raising gardens. Masonry is a great option if you’re looking for something that lasts longer than wood and are prepared to spend the money.
Your soil may become more acidic due to cement blocks. These effects will not last for long and can be replaced with acidifying fertilizers if necessary (source).
To Avoid Woods When Building Raised Beds
The following woods, despite what you might have seen on social media is not safe to be used in a raised yard:
Railroad ties and utility poles
Woods from recycled woods of unknown origin
Recycled woods which were not pressure-treated prior to 2004
Railroad Ties and Utility Poles
Because of their strength and availability, railroad ties and utility poles are popular choices for gardeners. The chemicals used to treat the wood can leach into your soil. You should not use railroad ties or utility poles treated with creosote in your garden.
Creosote, a tar-like preservation agent that protects wood from a variety of insects and fungi, is used widely on industrial wooden structures. Creosote may contain cancer-causing chemicals, including between 200 to 400 chemical compounds. Creosote can be toxic to many plants. Therefore, using creosote treated wood in a garden will prove fatal.
Also, creosote-treated wood can’t be refinished or stripped.
Railroad ties and utility poles should not be used if you plan to grow vegetables or herbs. Although flowers may do better than others, it is better to avoid creosote treated lumber.
Recycled woods from unknown origin
Reclaimed or recycled wood is another popular choice. It is often economical and eco-friendly. It is best to not use recycled wood if you don’t know where it came.
Any chemicals used to treat, stain, or finish the wood will be leaked into the soil. It will be difficult, if not impossible, to determine which chemicals remain on the wood if you don’t know its origin.
Pentachlorophenol (penta) is a common preservative that can be used on residential and industrial lumber. Penta, a powerful herbicide and pesticide, is now restricted to pesticide use. It was once quite common on foundation pilings, laminated timbers and fence posts.
Penta can be toxic to both humans and plants. Do not plant your recycled lumber in a raised garden if you don’t know where it came from or what treatment it received. While other chemicals might be safe, Penta is not recommended for wood that has been treated with it.
Woods Recycled That Have Been Pressure Treated Before 2004
If you are looking to recycle wood and know the origin of it, you need to ask one more question: Was it pressure-treated prior to 2004?
The most common wood treatment used for residential projects, such as decks, play structures and raised gardens, has been chromated copper acetate (CCA) since the 1970s. The EPA was prompted to investigate claims that CCA wood leaked arsenic into soil due to growing concerns. Plants like lettuce, tomatoes, onions and basil were also accumulating arsenic after being exposed to CCA in raised bed.
The EPA investigation found enough evidence to indicate that CCA-treated woods have been unavailable for residential use since December 31, 2003.
It is unsafe to use wood from an old fence, deck or other residential structure for your raised beds in any future home projects.
Conclusion
Learn as much information as possible about the origins and history of any wood that you use to build a raised garden bed. You should not use recycled woods, particularly industrial materials such as railroad ties.
Wood treated after 2004 is safe to use in the garden. It is also readily available and cheap. Untreated lumber should be used only for your garden.
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