5 Worst Raised Garden Bed Materials

A good raised garden bed should be made of safe, durable and easy to use materials. The garden beds material you choose should be safe around people, pets, plants and soil. You don't want to plant crops, herbs and flowers on the garden bed where heavy metals and other chemicals soak toxins into the soil.

These toxins will eventually enter your plate, especially if you are growing crops to eat on raised garden beds. Here are some raised garden bed materials that you should not use to grow plants.

raised garden bed

  1. Methyl bromide tray

There are many ways to reuse wooden pallets. You can make vertical gardens, compost boxes, garden furniture, and even Christmas trees! If you plan to use wooden tray DIY raised garden bed, please pay attention to those beds marked "MB".

Methyl bromide (MB) is a broad-spectrum insecticide, which is extremely dangerous to human health. Local contact may cause skin irritation and burns, and long-term contact may cause pulmonary edema. If not treated in time, it will lead to convulsions, coma and even death.

This is why you should not use MB treated wood to build raised garden beds to grow crops for consumption. Although MB treated wood can kill fungi, pests, rodents and other insects, it has a negative impact on the Earth's ozone layer. If it is necessary to use the holding racket, please select the holding racket marked "HT".

Heat treated (HT) pallets shall be sterilized at a temperature above 132 ° F for at least 30 minutes.

  1. Polystyrene foam plastic cooler

Recently people started using their old styrofoam coolers as raised garden pots, but that's why this is a bad idea. The polystyrene foam cooler is made of polystyrene, and the National Research Council of the United States concluded in 2014 that it is a "possible carcinogen".

In 2018, the World Health Organization reclassified it as a "possible carcinogen", prompting some organizations to require a statewide ban on the use of polystyrene containers. In general, polystyrene is harmful to animals, marine life forms, birds and the environment.

Because it is non biodegradable, a large number of waste polystyrene foam products float in the sea, blocking the waterways, and sometimes killing animals who accidentally ingest and suffocate these plastic fragments. In addition, polystyrene foam can change the characteristics of soil, increase its pH value, and affect the overall growth of plants.

If you plan to use earthworms to keep the soil healthy, please know that large exposure to polystyrene microplastics will significantly reduce its growth and increase its mortality.

Now, is polystyrene foam a kind of plastic? Polystyrene foam is a foamed version of plastic made of styrene. You should also avoid materials containing bisphenol A (BPA).

All plastic products have a resin identification code that you should know. If the number reads 1, 2, 4 or 5, the plastic does not contain BPA, but if the number reads 3, 6, 7 or shows PVC, it indicates that it contains BPA and you should use it with caution.

  1. Railway sleeper

Railway sleepers, also known as railway sleepers, are treated with creosote and CCA, both of which are prohibited for residential use. Creosote oil is a combination of thousands of different chemicals, but the main ones are polycyclic aromatic hydrocarbons (PAH), phenol and heterophenol alcohol.

Creosote is a viscous oily liquid that is highly flammable. It is one of the most common insecticides that people use to protect wood. Although there are many DIY landscaping trends of railway sleepers treated with creosote and CCA, you should not join the trend. Long term exposure to creosote in railway sleepers is associated with skin cancer and scrotal cancer.

In addition, do not burn creosote treated wood (in fireplaces or outdoors), as this may release carcinogenic toxins into the air. When you use creosote treated wood to build a raised garden bed, harmful chemicals will seep into the soil, kill some plants, and eventually fall on your plate through the food you grow.

Note: If you have old railway sleepers in your backyard that you want to get rid of, please check your local laws to learn how to properly discard them.

  1. Pressure treated wood

Chromized copper arsenate (CCA) is a pesticide, which was invented in 1933 and registered in 1940. Its popularity peaked in the mid-1970s, about the same time that the Environmental Protection Agency (EPA) was established.

EPA reviewed the safety and effectiveness of CCA treated wood, and found that its arsenic composition posed a risk to humans, animals and the environment. Wood treated with CCA contains arsenic compounds and is intended to remain in the wood.

Prior to January 1, 2004, CCA treated wood was approved for residential use, but was later discontinued due to arsenic exposure. In order to protect wood, Canada introduced another technology called alkaline copper quaternary ammonium salt (ACQ) for commercial use sometime in 2004.

Although the toxicity of ACQ is lower than CCA, it contains a large amount of copper, which can penetrate into the soil inside and outside the raised garden bed. As the soil in the garden bed treated by ACQ will remain moist, copper will seep into the soil and eventually into the crops for food.

Although your body needs and absorbs a small amount of copper from food, consuming too much copper will lead to various health problems, including brain damage and liver failure. If not treated in time, it may be fatal.

raised garden bed

  1. Coal cinder block

Avoid the use of cinder blocks made of coal or fly ash, as this powder contains trace amounts of:


Other heavy metals

The coal ash is heavy and remains on the ground, while the coal ash is lighter and is taken away by smoke. According to the Environmental Protection Agency (EPA), long-term exposure to or drinking water contaminated with arsenic compounds from coal ash will increase the risk of cancer, cognitive impairment, behavioral problems, heart disease, congenital disability or children's bone growth defects.

Although there is little evidence that fly ash or other heavy metals can penetrate the soil, you need to avoid cinder blocks for safety reasons. If you have to use cinder blocks, please select cinder blocks made of concrete so that you can DIY the raised garden bed with concrete blocks.

Good raised garden bed material

Good materials will not damage your health, animals or the environment. Here is a list of some good raised garden beds that you can use to transform your backyard.

Galvanized steel
Log (log, branch)
Natural stone
Galvanized metal


The raised garden bed is very suitable for elderly gardeners and people with mobility difficulties; However, it is best to avoid using some materials when building garden beds. This is because the materials you choose to use to build garden beds will play a huge role in the health of you and the plants, as well as in the overall environment.