What is the Safest Material for Organic Raised Bed Gardening?

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raised garden bed

With the food supply chains becoming more strained every year, it is no surprise to see more people investigating the process of growing their food.

Growing food at home in garden beds can be challenging, and it helps if any doubts about materials can be researched and resolved before purchasing or building any garden bed.

What materials are safe for Organic Raised Garden Beds?

Any material that is inert and will last a long time is satisfactory and safe for growing organic food. The list below displays several we know of.

  • Natural stone.
  • Manufactured concrete.
  • Timber.
  • Corrugated steel, corrugated iron.
  • Polyethylene. (Tubs or pots)

We undertook many hours of research to find the best material for our situation, and we utilize several of the listed materials in our yard design.

During this research, we discovered many questions about raised metal garden beds. The more common question is, “do I need a raised garden bed, or can I plant into the ground?

Both methods are suitable; however, if there is reason to question the soil conditions where you are because of such widespread use of chemicals in our environment, it is logical to go with the raised garden beds to control the soil conditions.

The primary question is, what is the best material to make a raised garden bed? There are several choices as noted above, so, in this article, we suggest options on materials, the disadvantages of each type of material, and the expected life of each material.

For the record, we use corrugated steel garden beds for the food growing and have some stone edging on some lower gardens as well as logs, old fence posts, and garden wall blocks as a landscaping style of raised garden. It is a mix, but they work for us.

Now, how about we get into this article?

What are some options for building a raised garden bed?

  • Bricks.
  • Pavers stood on edge.
  • Natural stone edging.
  • Landscaping blocks.
  • Wood and timber planks.
  • Logs.
  • Old fence posts.
  • Corrugated steel sheets.
  • Rolled roofing iron beds

Sort the materials into availability, cost, climatic conditions, possible toxins, and expected lifespan. All of these conditions will be different because of your country and the economic factors at play.

These economic factors are changing quickly, and this might be why you are searching for information before starting to grow your vegetables. We use corrugated metal raised garden beds as explained in “Why use corrugated steel raised garden beds?

What are the disadvantages of these materials?

We have included a table to help describe the different factors affecting each material type.

MaterialDisadvantagesTemperature
sensitive?
Possible
toxins?
Potential
lifespan
BricksHolds heatyesnolong
Pavers on edgeHolds heatyesno long
Natural stoneTime to buildyesno long
Landscape blocksExpensiveyesno long
Wood and timberRots quicklynoyesmed
LogsRotsnonomed
Old fence postsNot commonnono long
Corrugated steel sheetsCan rust, sharp edgesyes?med
Rolled roofing ironCan rust, sharp edgesyes?med

Temperature sensitive means the material will be a heat sink in sunny weather. If it absorbs heat, it is temperature sensitive. Rocks will heat up during the day and can slowly release this heat during the night. This attribute can help keep soil warmer during cold spells.

Possible toxins are chemical treatments used to prolong a material’s life, like pine logs treated for rot protection. Some of these treatments can leach into the soil, and plants can potentially take them up.

Potential lifespan is how long we expect a raised garden bed to last when made with these materials. Stone could last for a hundred years, and a treated log may last for ten years. The weather in your location will play a significant role in determining the lifespan of the listed materials.

If you prefer timber garden edges and wonder if they will hold up over the years, “Does timber edging last?” is recommended.

What materials last the longest for raised garden beds?

Stone and cast concrete items, as well as clay bricks, will last the longest.

Not high, but very sustainable.

These are a great way to build raised garden beds, but they can be very labor intensive and absorb heat, so you should use them in areas you have designed to take advantage of the warmth they can generate at night.

If time is something you have plenty of, and the stones are plentiful, you can build very cheap, long-lasting, and good-looking raised gardens with this material.

The cast concrete products are expensive but pretty fast to put into position. They will last forever and can be relocated at a later date if you require them.

Stackable garden wall blocks.

Will garden soil rot or rust a raised garden bed?

Garden soil can rot wood and rust steel. The speed that this occurs is very dependent on a couple of things. The first is how hard the wood is.

We are in Australia, where we have some tough woods that can take decades to rot down, but they will eventually rot.

Soft woods like pine will last for up to a decade, but the chances of them rotting faster are pretty high. The potential to decay is why this type of wood is often chemically treated.

Corrugated steel beds will rust over time, and the soil type, water quality, and quantity will determine the speed. These beds often have a protective barrier on the inside face to prolong the life of these raised garden beds.

Birdies raised garden beds. Maybe the best available.

The soil types can cause rust when the soil is acidic, and in bad cases, the soil can be what is called acid sulfate, which has the potential to rust steel beds quickly while also being harmful to plants.

To avoid questions about soil quality, we make and maintain our organic soil as described in these articles. “Making organic soil for raised garden beds” is first, then “how to maintain organic soil in raised garden beds, “then add “Improve your garden soil with rock dust and chickens. ” All articles open in new tabs, so you don’t lose your place.

Are rotting garden bed materials harmful to vegetables?

There is a risk that the chemical treatments in some woods can be harmful, so we recommend using natural lumber without treatments to minimize the risk of chemical leaching.

There are some questions about the coatings applied to the inside of corrugated steel beds, but we can find no research that points to any dangers.

We use this style of raised garden bed for most of our vegetable growing, and we are confident that the long-term risks are minimal.

Do raised garden beds need sealing inside?

Some metal raised garden beds come coated with materials to prolong the garden bed’s life, and if these protective barriers were to break down over time, it is unlikely they would cause harm.

The water movement from watering the plants in these beds will/should wash the particles lower into the soil column and away from the roots of the plants.

You can line timber garden beds if you wish, but no matter what you put on the inside, the risk of water getting caught between the outside of the sealing barrier and the wood is still there. It may even hold the moisture in that location for longer in some cases.

Conclusions.

The safest materials to make raised garden beds are the most natural ones, but they can come with hefty price tags or take a lot of time. What matters is getting the garden beds up and filled with vegetables.

Food prices are rising daily, so the time is now to start growing your own if you haven’t already.

Article by Tim Blanch for TheTropicalHomestead.com. He is a qualified Permaculture designer.