Raised garden beds are an excellent addition to any backyard, allowing you to grow your vegetables and sometimes fruits as well. Garden beds are usually constructed out of wood, but some prefer using metals for their durability and other desirable properties. Aluminum is one metal that I advise against using for raised beds.
Aluminum is unsafe for raised garden beds due to the risk of aluminum leaching into the soil. Although the levels needed to cause toxicity in humans are high, the plants are likely to suffer. Other metal options are available if you prefer not to use wood.
This article will cover more about how using aluminum in raised garden beds can impact your garden’s health. I’ll also suggest other materials to use instead of aluminum or wood, and review how aluminum leaching into soil potentially affects your health.
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The Effect of Aluminum on the Soil and Plants
Aluminum is highly reactive, which is why its ions can leach into the soil of your raised beds. Even if you aren’t growing any food in your raised beds, the aluminum in the soil impacts the plants in several ways.
- Firstly, aluminum can stunt the growth of many plants.
- Not only that, but research shows that plants suffer from ‘aluminum stress’ when exposed to high levels of metal from the soil.
- Generally, plants that suffer from aluminum toxicity show reduced root growth (source).
In other words, if you want your plants to blossom and thrive to become a luscious garden, keep them away from aluminum ions as best you can.
The Truth About Consuming Aluminum
Many people are misinformed about how aluminum impacts our health. Aluminum can be toxic at high levels, but we are continuously exposed to aluminum in a variety of different ways without any side effects.
When it comes to the material used in raised garden beds, the concern is about trace amounts of aluminum leaching into the soil, through the plants, and eventually onto your dinner plate. Most of us regularly consume low levels of aluminum in various forms – antacids, food coloring, preservatives, and other additives.
Aluminum Toxicity in Humans
The only time you should be concerned with aluminum toxicity is when a large enough amount of aluminum enters the bloodstream. While many people worry about developing Alzheimer’s disease as a result of aluminum toxicity, there is actually no scientific evidence linking the two (source).
The truth is, that using aluminum to build your raised garden beds will not pose the risk of developing aluminum toxicity immediately. However, there is some concern about continued exposure over long periods.
Some health experts advise against the use of aluminum in cooking pots, especially for cooking acidic foods. This information tells us that the risk of aluminum toxicity is real, even at lower doses. As such, I recommend you avoid using aluminum for raised garden beds.
If you intend to use aluminum, make sure it is galvanized to ensure it is nonreactive and resistant to pH changes.
How Aluminum Leaches into Soil
As I’ve stated earlier, aluminum is a highly reactive metal. With continued exposure to moisture (from the rain, watering the plants, or the weather), aluminum tends to oxidize rather than rust. Oxidizing means that molecules on the surface are free to mix with other chemicals.
Aluminum ions that form around most plants find a way to enter through the roots. Then, the metal’s high reactivity enables it to wreak havoc on the plant cells. To most plants, exposure to aluminum ions is toxic, but there is no problem when they are exposed to the metal as a mineral or as pure metal (as in foil).
Low pH (acid soil) is one of the most common ways that aluminum ions can leach into the soil. Most plants thrive in neutral or near-neutral pH, with some showing a preference for slightly acidic soil (source).
Other Materials To Use
Traditionally, raised garden beds are made of wood that is resistant to rot. Woods like cedar and redwood are the most popular options available because they are highly durable, repel termites and wood rot, and are also aesthetically pleasing (source).
If you do not want to use wood, here are a few other options to consider:
- Galvanized steel: Any metal that is galvanized (coated in zinc) is safe because it is much harder to break down the zinc layer and leach out the ions.
- Corrugated metal sheets: These are cheap and easily accessible sheets of galvanized iron or steel that are used in roofing. Corrugated metal is generally resistant to rust and oxidation.
- Concrete: Concrete is very hard, making it an ideal choice for permanent additions to your garden. Do not put a layer of concrete below the soil because concrete blocks the absorption of water through the root structures.
- Bricks: One of the simpler methods to create a boundary for your raised garden beds is to build them out of bricks. It’s a standard construction material that is durable and strong enough to handle the weight.
- Cinder blocks: Cinder material is made from igneous rocks, and cinder blocks are made of those crushed-up rocks suspended in a mixture of sand and cement. The resulting blocks are lightweight and highly functional.
All these materials have a few similarities. Namely, they are resistant to moisture, durable, and strong. Whichever material you choose, ensure that it does not react with the soil, nor does it impact it in any other way.
Regardless of the material you choose to make a boundary around your raised bed, it should be neutral and nonreactive.
Using aluminum in raised garden beds is not advisable because there is a high probability of leaching aluminum ions into the soil. Most plants do not tolerate exposure to aluminum ions, even at low concentrations. Aluminum toxicity in plants causes stunted growth, but much higher levels are needed for aluminum toxicity in humans,
Overall, there are low-level health risks from consuming plants that have grown in aluminum-rich soil, which is why, despite its many desirable properties, most raised garden beds do not use this metal.
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