Is Steel Really the Safest Material for Raised Garden Beds?

When I consider raised bed materials, I often prioritize those that are the most natural, beautiful, durable, sustainable, and affordable. There's something else important to keep in mind—and that's safety.

Many gardeners avoid growing edible plants in raised 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.

If you have concerns about steel raised beds, I completely get it. I'm constantly going the extra mile to ensure my kitchen garden space is as organic and safe as possible so that I'm only feeding my family and myself with the good stuff. The last thing I want to do is pick a raised bed material that would undo all the effort I put into selecting the best soil, non-GMO seeds, etc.

Fortunately, steel is actually a very food-safe material for your raised-bed vegetable garden. Steel is also incredibly durable, sustainable, and beautiful, though, unfortunately, it's often not the most affordable option.

Before we look more at the safety of steel raised beds, let's explore the three top options for steel raised beds and learn a little about how each material is made.

These are the three different types of steel most commonly used in raised garden bed design.

Corten Steel

Corten steel (sometimes written as Cor-Ten steel for the trademarked brand) was developed to form that distinctive weathered appearance over time with exposure to the elements. The surface of corten steel oxidizes when it comes in contact with moisture, giving it that rusted patina, but unlike other metals, it seals itself once a certain amount of oxidation has occurred. That means it will never rust through, even without being treated.

Powder-Coated Steel

Powder coating is a process that involves applying colored polyester granules as powder and then baking them onto a metal surface. This technique results in a smooth, uniformly applied coating far superior to regular paint.

Galvanized Steel

Galvanized steel has had a zinc coating applied to the surface of the steel to prevent the formation of rust. Most galvanized steel is created by submerging the steel in a bath of hot zinc.

Is It Safe to Grow Vegetables in Steel Raised Beds?

I've seen many gardeners express concern that the zinc used in the process of coating steel will leach into their soil and contaminate their veggies. It's true that steel is often treated with zinc for increased durability, and it's true that a small amount of zinc can seep into your soil over time. This will not, however, impact the organic soil inside your raised bed.

Zinc is a mineral that's naturally found in soil and is a plant micronutrient. You actually need to take in a small amount of zinc to survive, and guess what... so do your plants! Plants need zinc to form strong roots, build their tolerance to cold temperatures, and support processes like the formation of chlorophyll.

No amount of zinc taken up by the soil or the plants growing inside your steel beds will ever be enough to negatively impact you or be considered harmful.

I can say with confidence that it is absolutely safe to grow edible plants inside of a steel container, whether that container is galvanized, powder-coated, or weathered like corten.

Steel itself is made from mined iron and is a sustainable and recyclable resource. While steel is not technically metal but an alloy, the word metal is often used to describe raised beds made of steel. So if your next concern is, "Okay, but are metal raised garden beds safe?", know that the answer is yes.

What Is Food-Safe?

Food-safe simply means that the material that comes into contact with food (in this case, the material it's being grown inside) will have no harmful effect on the consumer. Food-safe materials for growing edible plants include terra cotta, fabric, ceramics, some plastics (look for labels like "food-grade" and "BPA-free"), and untreated wood.

It's always a good idea though to use only those materials that you know the history of for your raised beds. Salvaged wood, for instance, could be treated with something not great for veggies, like lead, arsenic, or other heavy metals. Terra cotta pots are porous and can absorb particles from synthetic herbicides and fungicides if the gardener who used them before you didn't follow safe and organic gardening practices. If you don't know the origin of your material, assume it could contain toxins and err on the safe side by only using this material to grow plants you don't plan on eating.

When shopping for your steel raised bed, only purchase from reputable sources with well-rated products. Birdies has a line of steel raised beds called the Urban line. You can also find raised beds available at Edge Right, Gardener's Supply Company, and Veradek. If you'd prefer to create a custom design, search for steel designers in your area and ask them questions about their process.

While galvanized raised garden beds are safe, if you're buying second-hand and notice the interior of the bed is visibly corroded, again, err on the side of caution and choose a different bed.

Steel Is a Safe Material for Organic Kitchen Gardens

Not only are steel raised garden beds perfectly safe, they're also sleek and come in colors and finishes to suit all tastes. And when I say they're durable, I mean they will last a lifetime. They will never rot or swell with moisture—they really don't even require upkeep. You can't go wrong with steel as a raised bed material if your budget allows. You'll be enjoying the beauty of your beds for decades to come.

Have more questions about steel raised beds? We've rounded up all the other questions and concerns about this raised bed material we've heard members of the Gardenary community express and tried to answer them here.

If you're feeling stuck or intimidated over ordering the right raised beds or creating a garden in your landscape, you're not alone. Gardenary exists to give beginner gardeners a place where they can find all the resources they need to keep on growing.

If you're a DIY'er, my book, Kitchen Garden Revival, delves deeper into picking a location for your kitchen garden and then walks you through the planning, designing, and setting up of your raised beds, plus how to plant and tend your favorite edible plants.

If you're more an online-course-type of person, check out our popular course, Kitchen Garden Academy. Over eight modules, we walk you through the complete step by step to set up and grow in your own kitchen garden.

For maximum help setting up your own kitchen garden, find a garden consultant near you to come out to your space and tell them you're interested in steel raised beds.

I'm confident that you're going to love having steel raised beds if you choose to install them in your outdoor space, and we've got tons of resources to help you build your own gardening haven and start growing!