I like to grow a variety of vegetables in my container garden. I had some aluminum containers lying around and wanted to know if it’s safe to reuse them to grow vegetables.
No, it is not safe to grow food in aluminum containers because it can leach into the soil and is toxic to plants. The toxicity will damage the plant roots and stunt it’s growth. There needs to be a certain level of aluminum to damage plants but it’s best not to use it when growing vegetables.
There’s a lot more you can learn about using aluminum containers in the garden and its impact on humans and plants. I’ve also written about the effect of other metal containers on plants and what alternatives you have.
Is it Safe to Grow Food in Aluminum Containers?
Most gardeners have plenty of access to aluminum containers. While they’re often referred to as “tin can,” most of the canned goods we buy at the supermarket are actually stored in aluminum. Those containers typically go in the recycling bin, so why not use them for your plants?
There are a lot of misconceptions about the safety of aluminum and you need to understand its impact on humans and plants.
The Effects of Aluminum on Humans
The biggest concern with using aluminum containers is ingesting the metal. While large amounts of aluminum are dangerous, trace amounts are perfectly safe and won’t have a major effect on your body. In fact, many processed foods already contain aluminum!
It’s often found in antacids and other medicines. Some processed foods like cheese, grains, and salts use it as an additive as well.
There’s a common misconception that aluminum can cause Alzheimer’s disease. But, there’s no solid evidence to support that claim.
Chances are, you’re already consuming aluminum on a regular basis. The effects that using aluminum will have on your plants, if any, will likely not make a difference to your overall health.
The Effects of Aluminum on Plants
The biggest thing you’ll have to worry about is how an aluminum container will affect the growth of the plan. Aluminum can alter the chemistry of the soil, which may have adverse effects on the plant. More on that soon.
Not only that, but aluminum is an excellent thermal conductor. When you place that aluminum container in the sunlight, it’s capable of heating the soil up to extreme levels. This can ultimately kill your plant!
Does Aluminum Leach Into the Soil?
Aluminum is capable of leaching into the soil. Herein lies the problem with using aluminum containers.
The metal has a reputation for being rust-proof. It’s true that aluminum cannot rust. However, it does oxidize. Rust and oxidation are two different concerns.
With continual exposure to water and atmospheric oxygen, aluminum will develop a fine layer of oxidation. This appears as a white powdery coating.
Because you’re going to be constantly watering the plant, oxidation is pretty common with aluminum container gardening. When this happens, the resulting oxidation will leach into the soil and affect your plant. This is referred to as aluminum soil toxicity.
What is Aluminum Toxicity?
Aluminum toxicity occurs when high levels of the metal leach into the soil. It can have a dramatic effect on plants.
You see, aluminum lowers the pH level of the soil. You can use this to your advantage if you’re growing plants that like acidic environments. However, you must do so in moderation to avoid any potential issues.
Once that pH level dips to dangerously low levels, the plant suffers. It can experience a host of developmental issues.
The most notable is short roots. Aluminum toxicity can stunt the growth of the root system by about half! To make matters worse, it doesn’t take that much exposure to do some damage.
Research has shown that only five to 30 minutes of exposure to high amounts of aluminum will reduce the future growth of plant roots.
On top of poor roots, the plants will experience nutrient deficiencies. The entire plant suffers here. The stem will become weak while the leaves show stunted growth and dull color.
Overall, aluminum toxicity will prevent the plant from thriving. For this reason, many gardeners avoid using aluminum containers. You can see some success if you’re only using the container to start the plant. But it’s best to avoid long-term growth in the container.
Is It Safe to Grow Vegetables in Metal Containers?
Growing vegetables in metal containers come with a lot of risks. While you won’t see any ill-effects from aluminum, the same can’t be said about other metals.
Many metals are dangerous for human consumption. Because soil is notorious for leaching trace elements from containers, there’s always the risk of plants absorbing contaminants into the tissue. This could result in toxic crops!
To be on the safe side, most recommend that you avoid using metal containers. Here are some specific metals to avoid.
Lead
Lead is a naturally occurring metal with a history of causing trouble for human health. In the past, it was frequently used in everything from paint to containers.
But, studies since then show that lead can cause life-threatening illnesses. This includes kidney damage, brain damage, anemia, and more. To avoid lead poisoning, several laws regulate its usage. But, that doesn’t mean that you don’t have lead containers laying around.
Avoid using lead at all costs. Not only can it affect the vegetables that you grow, but its mere presence in the garden could put kids and pets in danger.
Tin
Older tin cans can be problematic, too. Like lead, it can cause organ failure and other health issues.
The problem with tin is that it starts to break down when exposed to oxygen. This will only speed up the rate of absorption by your plant.
Older canned goods used tins, but they often had a coating of BPA to prevent oxidation. Consuming BPA is no better than consuming tin, so it’s best to avoid older tin cans altogether. Instead, use a safer aluminum can.
Galvanized Steel
Galvanized steel is a material that holds up well to weathering. Manufacturers treat the metal with zinc, iron, and a host of other chemicals to create that resilient finish.
While it will do a fine job of avoiding rust, there is the risk of zinc leaching. The metal releases into the soil and may affect the surrounding environment for years!
Zinc isn’t as toxic as something like lead or tin. But, it’s still harmful in high concentrations.
What Containers are Safe to Grow Vegetables In?
If you’re worried about how aluminum or other metals affect your plants, don’t fret. There are plenty of other container materials to choose from. To be on the safe side, stick with the following materials.
Terracotta
Terracotta is one of the best materials you can use! It’s made out of porous clay. Potmakers can mold the material into a bevy of shapes and designs, too. So, you can easily use the pots to spice up your garden.
Terracotta pots also hold onto water well. They can reduce evaporation rates while also getting rid of excess moisture. The material acts like a wick to regulate moisture levels.
Food-Grade Plastic
Plastic containers are a good option, too. They’re lightweight, versatile, and pretty affordable.
The only caveat is that you must use food-grade plastics. Cheaper plastics can leach chemicals and toxins into the soil just like metal. However, plastics tend to leach more because they get more pliable in the heat.
With food-grade plastics, you don’t have to worry about that! The material is dense and resists the effects of heat.
Concrete
Concreate pots are heavy, but they have many of the same benefits as terracotta. The material is porous and holds onto moisture quite well. As long as they have appropriate drainage holes, they can support your plants at any stage.
Peat
Finally, we have peat pots! Peat pots are made out of compostable wood and peat. Perfect for seedlings, this material is lightweight and flexible enough to use anywhere.
Like other porous materials, it holds onto water well. The best part is that it decomposes over time.
If you’re planting long-lasting perennials, you can easily stick the entire pot into the soil when you’re ready to transplant! It’s a zero-waste option that can serve you well.
Fact Checked, Written, and Published by Kevin Rodrigues
Kevin is the founder of Gardening Mentor, a website that aims to teach people to grow their own food in a limited space. As a self-taught gardener, Kevin has spent several years growing plants and creating gardening content on the website. He is certified in Home Horticulture and Organic Gardening from Oregon State University. He has a Post Graduate Diploma in Horticulture and Landscape Gardening from Mumbai University.
Read more