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When considering raised garden bed materials, people often prioritize those that are the most natural, beautiful, durable, sustainable, and affordable. There's something else important to keep in mind—and that is safety.
Many gardeners avoid growing edible plants in raised garden beds made of steel over concerns that the metal will leach dangerous chemicals into the soil and therefore into their veggies. It's true that plants can absorb both the good stuff (nutrients) and the bad (heavy metals and poisons) that have dissolved in their water supply.
Fortunately, steel is actually a very food-safe material for your metal raised garden bed . Steel is also incredibly durable, sustainable, and beautiful. Galvanized steel is one that most commonly used in raised garden bed design. It has a zinc coating applied to the surface of the steel to prevent the formation of rust. Galvanization is the process of bonding a layer of zinc to the surface of steel or other ferrous metals like iron. This process prevents the steel or iron from rusting when it is in contact with moisture.
What’s Galvanized Steel Used For?
Galvanized steel is the preferred material for watering troughs for livestock, exteriors of grain silos and water storage containers, shed construction, roofing, gutters and downspouts, and a number of other products. It’s sometimes used as durable fencing panels.
For decades, galvanized steel pipes were the standard for home water pipes, too. While this is no longer the case as galvanized pipes have been replaced with PVC and copper, most older homes still have galvanized fittings in use. As long as the zinc coating remains intact, these pipes will continue to last for years to come.
Is Zinc Leaching From Galvanized Metal?
Zinc is a normal component in most soils. Plants and humans both need a small quantity of zinc to survive. You’ll find it in your daily multivitamins too! Plants need less zinc than we do, but it still is a necessity. The microscopic amounts which they may absorb from your metal raised garden beds won’t harm any food you’re growing, nor should it be harmful to the plants themselves.
Steel is an alloy of iron and carbon. It is very unlikely for notable amounts of zinc to leach from the coating into your soil. It takes very acidic conditions and many, many years for a galvanized zinc coating to break down. But it will be extremely minimal, and some plants may actually prefer the slight zinc boost in the soil. As long as the steel is from a reliable manufacturer, there is no need to be concerned that your metal raised garden beds will leach toxic materials.
Metal Raised Garden Bed Selection
So we can draw the conclusion that well-made galvanized steel garden beds are totally safe to grow food in! (Note the emphasis on well-made, so choose reputable and well-rated products!) I am partial to the metal raised garden beds designed by Anleolife . These sturdy galvanized raised beds are extremely effective. Each container is designed with utility in mind, allowing you to choose the exact size and shape you need!
Keeping Your Metal Raised Beds Safe
Zinc-coated steel is sturdy and will hold up to most garden uses. But there are ways to ensure your containers are safe for decades to come!
Avoid acid soil and water. In order to further prevent a small amount of zinc from seeping into the soil, do not use high acid soil and water or improver in the metal raised garden bed, because acid is the cause of decomposition of galvanized steel over time.
Avoid using fresh chicken manure in your garden. While it’s amazing stuff, its acidity will break down the zinc surface of your metal raised garden bed more quickly, opening the steel up to a risk of rust. Instead, use composted chicken manure or other organic options.
Opt for plants that will grow in neutral soils, and keep the soil pH on the neutral side. At a neutral level, the zinc is less likely to break down into the soil. If you’re planting acid-loving plants in a metal raised garden bed, consider a liner. Heavy plastic can keep acidic soils from making direct contact with the metal. Just be sure that the plastic only covers the sides to allow for good drainage.
Amend heavy clay soils to loosen them up. Well-draining soils are necessary for mental raised garden beds to ensure they don’t turn into muddy ponds. In addition, clay is such a fine particulate that it can cling to the sides of your metal raised garden bed, and the caked-on layer of clay will do more damage to the zinc finish than a sandy soil would.