Raised beds are already famous among gardeners, but metal ones have particularly become a favorite for many reasons. They have durable and sturdy designs that you can place at the ideal height to tend to them without kneeling. And they’re available in various colors, sizes, and shapes.
Galvanized metal is safe for raised garden beds as long as you use a linter to keep the soil off the metal directly. Other metals in galvanized steel include aluminum and zinc, neither of which will harm your plants or you as long as they’re in small amounts, so some corrosion is not an emergency.
However, many people have started questioning the effectiveness and safety of using metal for raised beds. So let’s see if you can use metal for raised beds, if it’s safe, and if it provides any benefit. We’ll also examine how you can plant in a raised garden bed.
Can You Use Metal for Raised Garden Beds?
You can go ahead and use galvanized metal for raised garden beds without a problem. In fact, metal raised beds are becoming one of the most popular options, especially since they have so many advantages.
They’re sturdy, durable, resistant to damage, and can’t rot like wood. As a result, they can last for even decades. Plus, they add an industrial look to your garden. They also won’t contract, swell, or need to be painted or oiled for maintenance.
What is Galvanized Metal?
Metal typically rusts after a few months because of different elements like moisture. However, metals like zinc and aluminum don’t rust. This is where galvanization comes in. The process involves using metals that don’t rust to coat metals that tend to corrode (ferrous metals like iron or steel).
Galvanized steel is usually made using a hot-dip process where smooth or corrugated sheet steel is submerged in molten zinc, creating a uniform layer on the surface. In some cases, the metal is allowed to cool down so that the material fully bonds to the metal before it can be re-dipped for another coating.
Typically, pure zinc is used for galvanization, but some metal is also hot-treated with some alloy. For instance, aluzinc, a combination of zinc and aluminum, is used for hot-dipped galvanization. The aluminum makes an outer layer that protects the zinc and the inner steel layers from damage due to moisture.
What are the Advantages of Galvanized Metal Raised Beds?
Raised garden beds made of galvanized beds have numerous benefits. Let’s take a look.
Lasts a Long Time
Metal is typically damaged by rust. However, galvanized metals don’t rust that easily, which means they can last for quite a while. Most galvanized metals can last for at least 50 years or even more! And since they last so many years, they make for a great investment.
Durable & Reliable
When you use a galvanized metal frame for your raised garden bed, you can be sure that it won’t collapse or fall all of a sudden. They’re also effortless to use since there’s no construction involved.
Helps Extend the Growing Season
Since galvanized metal raised garden beds are made of metal, they conduct heat, store the sun’s heat, and heat the soil close to the raised bed’s edge. This heat can help to extend the growing season. So, for instance, you can use it for heat-loving plants in mid-late autumn.
Keep Out Animals
Another benefit of galvanized metal raised beds is that they keep burrowing animals at bay. So if you’ve been having difficulties with rabbits, look for a raised bed at least 3-4 feet tall.
Is it Safe to Use Galvanized Metal for Raised Beds?
Despite popular belief, it’s safe to use galvanized metal for raised garden beds.
If you still have doubts about the material being unsafe for your garden beds, think about it: most water pipes use galvanized metal. Similarly, in the past, it has been used for many water- and food-related items like water storage, livestock watering troughs, and grain silos.
Since galvanized metal is made by bonding zinc to the surface, many gardeners worry that the zinc will seep into the soil and harm the vegetables and plants. However, zinc is a plant micronutrient. This means plants need it in small amounts to make photosynthesis more efficient.
So some amount of zinc will seep into the soil over time. However, it doesn’t harm the vegetables or plants, and the small amount is still beneficial for the plants. And just like plants, we also need zinc in small quantities. So as long as it’s in minor amounts, it won’t harm us, but high exposure to it is toxic to both the plants and us.
Plus, raised beds made of galvanized steel are durable and will have to be exposed to a high amount of acidic compounds for the steel to start breaking down. And since most soils are pH neutral, it’s doubtful that your garden bed will be damaged.
What About Aluminum?
Just like zinc, there’s no significant risk of aluminum from aluzinc leeching into the soil or the environment. Aluminum is lighter than zinc when it’s in molten form and will rise to the outer surface as it goes through the heat-dip process.
As a result, it will create a very thin protective layer over the zinc and prevent zinc from leaching. And if there’s an additional coating over the aluzinc, like paint, it adds a secondary layer of protection.
Aluminum is also not as soluble as zinc, which is why it’s used in food storage. Plus, it’s resistant to acidic conditions, making it a good pairing with zinc. And since the garden beds won’t heat to hundreds of degrees, the limited amount of aluminum in aluzinc is safe to use and prevents the zinc from degrading.
How to Plant in a Metal-Raised Bed
Planting your choice of vegetable, fruit, herb, or flower is relatively easy in a metal raised bed. Here’s what you have to do.
Lay Down Landscape Fabric
Moles and weeds can quickly wreak havoc on your raised garden beds. To prevent that from happening, you should lay down a layer of durable landscape fabric like this one from Extraeasy (on Amazon).
Add Crushed Limestone
Put a few inches of crushed limestone on top of the landscape fabric. You can also line the borders of the fabric with large stones to keep the gravel right where it belongs.
Most people believe that raised beds need a lot of soil. However, while they require soil, they don’t require as much as you think. In most cases, you’ll only need to add just one foot of high-quality soil, so instead of filling the entire bed with dirt, you can use a filler.
So, you can add around 6 inches of pea gravel like this one from Mighty109 (on Amazon) or use a mixture of sand, pine cones, and packing peanuts. Then, put landscape fabric over it to prevent the soil from washing away.
Add Soil and Compost
Finally, all left to do is add high-quality compost like this one by Charlie’s Compost (on Amazon) and topsoil like this one from Organic Plant Magic (on Amazon). If plugs are at the bottom of the metal tank, remove them to allow proper drainage.
Other Tips to Remember
To make sure you get the best results from your galvanized metal raised garden bed, keep the following tips in mind:
- The best soil for your raised garden bed is a lightweight soil mix since it can retain moisture so that you don’t need to water the bed often.
- Avoid using sandy, loose soil since water will flow through it quickly, and you’ll have to water the bed frequently.
- Also, avoid using highly acidic soils in your bed to prevent the small amount of zinc from leaching into the soil.
- Don’t add something acidic to your soil since it will cause the galvanized metal to break down with time.
- If you want to grow plants that need acidic soil, put plastic liners on the sides of the bed to prevent the metal planter from coming in direct contact with the soil.
- Drip irrigation or soaker hoses are the best options for watering raised garden beds.
- Water the soil around the plants’ base deeply. Don’t water their flowers or foliage.
- Adding mulch to the raised garden bed can help prevent evaporation so that it retains water for longer.
- Water plants early in the morning before the sun reaches its peak to make sure the plants get the required moisture before it starts to evaporate.
- Choose a location that doesn’t receive the sun all day to prevent it from drying out or heating up.