What Is Corten Steel?

"I'm not taking gardening advice from a woman whose raised beds are completely rusted!"

That was a comment on one of my YouTube videos for the Gardenary channel. This person might be shocked to know that I actually bought the bed to look like that. It's intended to be rusted.

Corten steel (sometimes written as Cor-Ten steel for the trademarked brand) was, in fact, developed to form a weathered, rust-like appearance with exposure to the elements. Also called weathering steel, this material eliminates your need to paint or treat your raised beds with anything.

The material will develop a rusted patina on the surface, but (here's the important part) it will never rust through—at least not in this century. You might associate rust with old pieces of scrap metal on their last leg, but Corten steel actually has incredible resistance to corrosion.

When choosing materials for raised beds that will be used in a kitchen garden, we prioritize those that are natural, beautiful, durable, sustainable, and also affordable. Corten steel is not the most affordable option out there, but you cannot get much more durable than steel, which will quite literally last a lifetime.

Corten steel has grown rapidly in popularity, and many of our Rooted Garden clients also choose corten steel for the beauty of the weathered look. I myself chose to install Corten steel raised beds in my own Nashville garden after growing in cedar raised beds for years.

Though a Corten bed itself can cost you a pretty penny, you'll save money in the long run by not having to replace rotted materials. I consider them an investment in being able to enjoy your gardening space to the fullest for decades to come.

Let's look at the other benefits of using steel in your kitchen garden.

What Are the Benefits of Corten Steel?

Corten steel beds have thin sides, and this narrow profile allows you to maximize your growing area, especially if you're growing in a small space. You can give nearly all the space to your plants while still having a super strong garden bed that will never give up growing. 

Here are some of the other major benefits of using steel, if your budget allows:

• Corten steel is a sustainable resource.
• The soil in a steel garden will warm up faster than a wood bed in the spring, meaning you can start gardening sooner.
• In the fall, the raised beds will insulate plants inside during cold spells and keep the soil temperature more consistent.
• Steel is a food-safe material (more on that in a bit).
• Corten beds can withstand corrosion and won't chip, crack, or peel.

Corten steel is also readily used to make garden edging, planters, and even fire pits, so you can easily match your raised beds to existing features of your home for the most cohesive look.

We hired a steel designer to create the custom Corten beds pictured above for a client to match her gorgeous fire pit pictured below. From her living room window, she can fully enjoy her elegant outdoor sitting area and Corten hardscapes.

Pro Tip for Ordering a Corten Steel Raised Bed

The first time Corten steel beds were delivered to a garden installation I was doing, it felt like opening a present on Christmas day—and this wasn't even my garden! I learned one important lesson though that I keep in mind when using steel materials for clients: Steel is heavy.

With that in mind, make sure you arrange for delivery of your Corten steel raised bed. I've ordered beds from steel designers that took four grown men to carry them off the truck and maneuver them into the yard. Many arrive pre-made, so measure the narrowest part of the path the bed will have to travel to ensure it will fit through.

Ask the delivery men to place the bed in the exact spot you'd like it to stay.

When selecting the size of your raised bed, I recommend going with something two feet tall, a height that's mostly for ease of tending for the gardener. Most of the plants you'll want to grow inside your raised bed will require at least 18 inches of depth for their roots.

For more details on selecting the right raised bed for your space, check out our complete raised bed guide.

Is It Safe to Grow Vegetables in a Corten Steel Container?

I get this question a lot—it seems many of you are concerned that the zinc used in the process of coating the steel will leach into your soil and contaminate your veggies. I can say with confidence that it is absolutely safe to grow edible plants inside of a steel container, whether that container is galvanized, power coated, or weathered like Corten.

Steel itself is made from mined iron and is a sustainable and recyclable resource. Steel is often treated with zinc for durability, and while a small amount of zinc may seep into your soil over time, this will not impact the organic soil inside the 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!

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

Do Corten Steel Raised Beds Get Too Hot During the Summer and Burn the Plants?

I was really intrigued by Corten steel from a design standpoint when I first saw it. I'd just started designing kitchen gardens in Houston and had a client who wanted raised garden beds to match her beautiful Corten steel fire pit. My concern, I told her, was that Houston's summers were just way too hot for such a raised bed material.

Then I visited Houston's Levy Park with my family and saw plants happily growing in Corten steel raised beds in their community garden. In summer! That was enough to convince me.

I found a steel designer to build and install the raised beds for my client, and her garden thrived year round!

Clients often share similar concerns about metal trellises overheating and burning the climbing plants growing on them. I can report that we've never had an issue with metal in the garden, even in Houston's triple-digit heat.

Do Corten Steel Raised Beds Have Good Drainage?

Most of the Corten steel raised beds you will find online to order are actually bottomless. As long as you choose a good soil that drains easily, your bed will have ideal drainage and keep your plants happy and thriving.

A Corten steel container with a bottom, like the large Corten steel container on wheels for sale in the Gardenary shop, most likely comes with drainage holes if it's intended for gardening. If you find a container without them, it's simple enough to drill your own drainage holes every six inches or so to allow the water to pass easily through.

Do Corten Steel Raised Garden Beds Arrive Rusted?

Most Corten steel will arrive looking "newer"—by that I mean the sides will be a dark gray color with some stripes that hint at an aging process. This is Corten's bare steel finish. Over the next couple of months, the material will weather and develop that classic golden brown color and a rougher texture. In the picture below, you can see my large raised bed during the weathering process.

While the beds are undergoing their weathering process, it's best to keep them off concrete or light-colored stone that could potentially be stained. I kept mine on dark-colored gravel.

How long this weathering process will last depends on your climate. If you have frequent rain followed by sunny weather, your beds might oxidize faster than those in a drier area. Overall, the process should be complete within about 6 months.

What Are the Bonuses of Corten Steel from a Design Standpoint?

Corten steel has so many benefits from a purely aesthetic standpoint. First, you can find ready-made beds in all heights and lengths online, or you can go fully custom and design something truly unique for your space, such as these beloved half-moon shaped Corten steel beds featured in my book, Kitchen Garden Revival, and pictured below.

I love how the rich patina of the raised beds pulls all the warmth from the fence and compliments the jewel-tone shades of the Swiss chard and the greenery of the kale.

The weathered appearance of Corten is definitely a look, and it may not work for every garden or appeal to every gardener's taste. If you prefer a more sleek, modern feel, you might lean toward powder coated metal, which has a smooth finish but is equally durable.

Where Can You Buy Corten Steel Raised Beds?

The Gardenary shop has recently begun carrying three incredible Corten steel raised bed kits that can ship right to your door and require minimum assembly.

Birdies has a line of Corten 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.

You're Going to Love Corten Steel Too!

I really don't think you can go wrong with Corten steel. You'll be enjoying the beauty of your beds for decades to come.

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.

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 Corten steel.

I'm confident that you're going to love having Corten 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!