Do Metal Raised Beds Get Too Hot to Grow in?

Can You Garden in Metal Raised Beds in the Summertime?

Don't metal beds get too hot? I don't want to burn my plants.

I hear this a lot, and I totally get the concern. Soil is, after all, really good at absorbing heat, so it would make sense for the soil in metal raised beds to be scorching in the summer.

When I first started designing kitchen gardens, I avoided metal and stuck with my little wood raised bed kits. But then I had a client who loved the weathered look of Corten steel and wanted some custom metal beds to match her new steel fire pit. "I think a Corten steel raised bed would be so beautiful from a design standpoint," I told her. "But this is Houston. In June. We're gonna hit triple digits like every day next month. You won't want to have metal beds on those days."

But my client was pretty insistent. Right around that time, I visited Levy Park with my family. They have a little community garden, and guess what raised bed material they used? Corten steel. And the plants in those raised beds were thriving, even though it was the middle of summer!

That was enough to convince me, so I found a steel designer to build and install the Corten steel raised beds for my client. She absolutely loves them, and her garden is productive year round. I can happily report that none of my clients have ever had any issues growing in their metal raised beds. Nor have I.

Even though I've designed and planted dozens—maybe even hundreds—of gardens with metal raised beds at this point, some people still don't believe me that metal raised beds won't burn your plants in the summer. So I put my own garden to the test.

Metal Raised Beds Temperature Test

I picked a summer afternoon to test the soil temperature in my Corten steel raised beds. First, I used a soil thermometer to measure the soil temperature in the ground. I selected a spot in my native plant and pollinator garden space that gets full sun. The soil in the ground was about the same temperature as the air (89°F).

Then, I checked the temp of the soil in the middle of one of my raised beds that also gets direct sun exposure. It was also the same as the air temperature (89°F).

Finally, I moved the soil thermometer to the very edge of the raised bed, right up against the steel side panel. The soil next to the steel measured about 8°F warmer. So the metal sides definitely do raise the temperature of the soil that comes in close contact with them.

This doesn't mean you're going to scorch all your plants. The key to handling this temperature change in your soil is just to plant appropriately. Let's look at how to plant in metal raised beds.

How to Plant up Metal Raised Beds in the Summer

Here's the trick to planting in steel beds during the hotter months of the year: Plant more heat- and drought-tolerant plants like flowers and perennial herbs around the outer edges of your beds, where the soil will be warmer. Put plants that are more sensitive to temperature and that will want more moisture in the middle of your raised beds, where the soil will be the same temperature as the air.

Plants that are great for planting around the edge of your raised beds include marigolds, oregano, thyme, sage, rosemary, green beans, vincas, and zinnias. All of these plants were thriving on the edges of my steel raised beds in summer even though the soil around them was almost 10° warmer than in the center of the bed.

Of course, you want to make sure that you're filling your entire garden with plants that like the current temperatures, right? Something like okra loves 95-degree-weather, so it's not going to mind warm soil one little bit. Lettuce and carrots, on the other hand, would mind. So always plant for your growing season. Stick with plants that like growing in heat during your hot season, and you'll be just fine.

Follow this planting plan, and you'll have a productive kitchen garden in your metal raised beds this summer.

More Tips to Grow in Metal Raised Beds

In the warmer months, your soil might dry out quickly. Make sure you have a consistent watering method (like drip irrigation) and check on the moisture level in your soil daily. You don't want plants to get thirsty and then feel stressed out.

If you want to extend the growing season for plants that like warm but not hot weather, consider covering your garden with shade cloth. This will keep the air and soil underneath the cloth a couple degrees cooler. That in turn can prevent your plants from getting scorched or going to seed too soon.

The Best Types of Metal for Raised Garden Beds

These are the three different types of metal most commonly used in our raised garden bed designs.

Corten Steel

Corten steel (also written as Cor-Ten steel for the trademarked brand) has a distinctive weathered appearance. Even though the surface looks rusted, it only oxidizes to a certain point before stopping. This differentiates it from other metals.

Powder-Coated Steel

This is the best type of metal for sleek, modern appeal. To get a smooth outer coating, colored polyester granules are applied as powder and then baked onto the metal surface.

Galvanized Steel

Steel is galvanized by being submerged in a bath of hot zinc. This prevents the formation of rust on the metal. Galvanized steel is typically your best budget option.

The Benefits of Growing in Metal Raised Beds

Now that you're no longer worried about growing in metal raised beds, let's consider why so many people are turning to them as an alternative to wood raised beds as lumber prices soar.

Here are the benefits of metal raised beds:

• Metal beds have narrow profiles, which allows you to maximize your growing area.
• Metal is a sustainable material because it's recyclable.
• The soil in a metal garden will warm up faster than a wood bed in the spring. Here's when we can use the heat conduction of metal to our advantage!
• Steel, whether it's powder coated or galvanized, is a food-safe material.
• Metal beds will stand up to the elements much longer than wood raised beds.
• Metal beds don't require any upkeep.
• Some people prefer the more modern aesthetic of metal beds.
• Raised beds made of light metals like aluminum weigh much less than other planters, which is important if you're growing on a raised deck or balcony.

Overall, metal raised garden beds are an attractive, durable, and affordable option for your kitchen garden.

The Verdict: Metal Raised Beds Do NOT Get Too Hot for Your Plants

I've never had an issue with metal in the garden, even in Houston's triple-digit heat. That goes for metal beds and metal trellises. Now, you might not want to press yourself up against all that metal on the hottest and sunniest of days, but your plants, with their nice soil buffer, will be just fine.

Go with metal raised beds if that's what you're leaning toward, and you won't be disappointed. You'll enjoy the beauty of your raised beds for years to come.

If you're feeling stuck or intimidated about ordering the right raised beds for your garden space, we've got you covered. Check out my book, Kitchen Garden Revival, to delve deeper into picking materials for your garden and setting up your space so you're ready to grow all your favorite leaves, roots, and fruiting plants. For maximum help setting up your own kitchen garden, find a Gardenary consultant near you to come out to your space and tell them you're interested in metal raised beds.

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