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Using wood to create a raised bed is risky because treated lumber harms the soil’s microorganisms essential to growing healthy plants.
Untreated wood rapidly rots when in direct contact with moist soil. More durable woods, such as cedar, contains a natural fungicide that is detrimental to plants. While the wood merchants no longer treat lumber with chromated copper arsenate (CCA), the wood is still in circulation.
Using wooden raised beds is outdated and dangerous; several better options exist.
Why Switch from Wooded Raised Beds?
You might believe that I am against wooden products or attempting to sell you a product not made of wood, but neither of these is true.
Wood is a stunning material that may add tremendous value to a garden but should not be used as a planter or in constructing raised garden beds.
For optimal development, plants must have robust, healthy root systems. A healthy population of microorganisms in the soil is necessary for healthy roots, which in turn require a diversified population of microorganisms (billions). If you remove all the microbes, you will be left with dirt rather than garden soil.
I enjoy working with cedar wood because of its naturally dark color, which comes out after being treated with a stain and varnish. However, cedar oil is a component of tanner oils; therefore, building raised garden beds out of cedar wood is not a good idea for plant cultivation.
Growing resilient plants resistant to diseases and pests in untreated wood is possible. Unfortunately, the dyes and sealers on the market are not designed with biota in mind.
Their products are designed with an emphasis on appearance, with little thought given to the potential harm they may cause to the microorganisms in the soil.
Concerns surrounding the safety of widely used commercial wood preservatives, such as green-stained wood, have been around for some time. Many producers halted production after they learned that members of their production personnel were becoming unwell.
Because of the potential health risks creosote poses, recycled railroad ties and utility poles should be utilized to construct beds where food plants will be cultivated.
For USDA organic certification, no products made of pressure-treated wood in organic gardening may come into contact with crops intended for human consumption.
There are few practical options for safeguarding the wood used in flower beds. Linseed and tung oil are the two products sold the most, although there is little evidence to suggest that either treatment considerably extends the time wood may survive when it is buried in the ground.
Building materials often include chemical compounds used as a first line of defense against insects and other organisms that could cause structural damage. These treatments are essential to make the wood more long-lasting. However, treated wood should never be used near growing plants.
Every 15 years, the Environmental Protection Agency (EPA) reviews the various applications of pesticides. Chromate-copper arsenate is one of these substances that is currently being investigated (CCA).
CCA is an acronym for pesticides containing chromium, copper, and arsenic. These pesticides protect the wood from termites, fungi, and other pests that can reduce the quality of wood goods or damage their structural integrity.
Linseed oil, derived from flax seed, can prevent rot in wood that has not been treated. Raw linseed oil is mixed with synthetic solvents, some of which are not permitted where food is grown.
Raw linseed oil has less efficiency as a wood preservative than synthetic wood preservatives. Keep in mind that wood that has been treated with linseed oil encourages the formation of mildew.
To facilitate application and absorption into the wood, tung oil, an extract of the tung tree seed, is routinely diluted with toxic solvents when used as a wood preservative.
Avoid using treated wood in your garden if you don’t want hazardous chemicals to leach into the soil and contaminate the food you grow. The only choice is to construct a raised bed out of untreated wood, but you shouldn’t expect it to last very long.
Wood is a valuable commodity but is not advised for raised garden beds. Consider wood-free alternatives for better gardening success when building or buying a raised garden bed.
Raised Garden Bed Materials: Aspects to Consider
- When deciding on the materials for your raised garden beds, the health of your plants and the environment in which they live should come first. The following is a list of things to take into account:
- Some plants should not be grown on raised beds that are too high. Plants such as sweet corn, beans, indeterminate tomatoes, and other similar plants can be planted in raised beds; however, the beds should be kept low for efficient administration.
- Cultivating disease- and insect-resistant plants without establishing a robust soil biota is impossible. Even though hydroponic gardening demonstrates that plants may be maintained without soil, a significant amount of work is required to maintain these settings to prevent the spread of disease. A single virus has the potential to wipe out a whole crop.
- Most plant species require between six and ten hours of daily direct sunshine for their photosynthetic processes to operate at peak efficiency. Use materials for the raised bed resistant to UV radiation’s effects.
- Check that the raised bed materials can withstand prolonged moisture exposure without decaying.
- No organic material is resistant to decay without some component of it being fungicidal.
- Although wood has, for many years, been the material of choice for constructing garden structures, it is becoming more and more apparent that wood is not a viable material for raised garden beds or planters.
- Even untreated, longer-lasting wood, such as cedar, can harm the soil biota necessary to produce hardy crops.
- The growing medium should have an appropriate balance of organic content, inert materials, topsoil, and a healthy and diverse population of microorganisms, providing optimal development support, plant hydration and nutrient availability, and adequate plant anchoring.
10 Frequently Asked Questions Regarding Raised Beds Answered
Can I use cinder blocks to build raised beds?
Cinder blocks are made of fly ash which contains some nasty stuff. According to an Indiana State University study, plants grown near fly ash can absorb arsenic, lead, and mercury, which could cause cancer and neurological damage.
What is the best material for raised garden beds?
The most durable material is natural stone and metal. Metal beds are easy to construct, durable, and can be made quite pretty.
How wide should a raised garden bed be?
Try and get a bed that allows you to reach the center effortlessly. A good width for any bed is 4 feet or 1.2 m.
How deep should a raised bed be?
Not less than 8 inches, but it depends on what you are growing. Shallow-root plants include some of the brassicas, and deeper-rooted plants are some of the Cucurbita (pumpkins)
What is the standard height of a raised bed?
There is no standard. Most raised beds are low enough to bend over, i.e., below your hip.
Why is wood, not a well-raised bed option?
Untreated wood decays rapidly when in constant contact with moist soil, and treated timber has health risks – either for the plant or the plant and you.
Are plastic raised beds any good?
It isn’t easy to make a plastic that is UV-stable. Most plastics deteriorate if exposed to the sun for extended periods, and some plastics may also become brittle when exposed to temperature extremes. Polypropylene is probably the most stable, but getting a food-grade polyprop may be challenging.
I’m thinking of buying a metal raised garden bed. What should I look out for?
Metal naturally oxidizes (rusts) when in contact with water and air, so look for a metal raised garden bed that is well-coated or made from an alloy. Aluzinc products that have been powder-coated are probably the most rust-resistant.
What are the advantages of a raised bed?
Controlling plant-growth variables like soil temperature and water drainage in raised beds is easier. Because of that, they allow you to start your crops earlier in the season and improve plant health. Raised beds also improve accessibility.
Does a raised garden bed need sides?
A shallow raised bed does not need sides; sides improve soil retention and reduce possible erosion.
Wooden raised beds are not good, especially if you want thriving plants. Plant well-being, resilience, and productivity are directly related to soil health, of which a diverse microorganism population is pivotal. Kill the soil biota, and you transform healthy soil into dirt.
Treated wood is infused with pesticides and other toxins that can harm your health, so stop using it in garden beds. Untreated wood decays rapidly, making alternatives to lumber a better choice.