Are Galvanised Steel Garden Beds Safe?

Raised beds have a number of advantages over traditional in-ground gardens. Not only do they allow you to customise the soil to suit whatever you’re growing, their height makes them much easier to tend to. 

Galvanised steel is often thought of as a good material for raised beds, but there’s a view amongst many gardeners that this material can have a harmful effect on our soil and plants. 

In this post, we’re going to debunk the myths about galvanised steel beds, and tell you why this is arguably the best material to use in the garden. 

What is Galvanised Steel? 

Before going into whether galvanised metal garden beds are safe, we should first look at what galvanised steel is.

Galvanising is the process of immersing metal into molten zinc. The zinc forms a coating which provides long-term protection against corrosion and rust. 

Aluzinc steel has the same durability, but it’s been coated with a mixture of zinc and aluminium.

Galvanised steel is used in a huge number of industries. It offers all the benefits of steel, with added corrosion resistance.

It’s often used as water troughs for livestock, storage containers, shed construction, roofing, gutters and much more. 

Are Galvanised Steel Beds Safe? 

There’s a widespread belief that galvanised steel beds can leach zinc into the soil. Zinc in the soil could get into the plants which, if you’re growing edible produce, would then be consumed. 

We’ll take a look in more detail later, but this doesn’t happen, or at least not to the extent that many believe it does. 

In short, galvanised steel beds are perfectly safe, and pose no health risks when it comes to zinc leaching. This is the case whether you are growing flowers or edible plants. 

What are the Benefits of Galvanised Steel Beds? 

One of the major advantages of galvanised steel is that it’s much more durable than other metals. An average coating of zinc can protect a steel structure for up to 100 years!

You can expect your galvanised metal garden beds can last up to 30 years, and they need very little maintenance during this time. There’s no need to oil or treat a galvanised steel bed, although many people do paint them in their preferred colour. 

While wooden beds will start to deteriorate over time, galvanised steel beds will be strong for over 30 years. 

Galvanised steel beds also look great! They have an industrial look that suits most gardens, especially when paired with thriving vegetables or brightly coloured flowers! 

Are there any Disadvantages? 

No material is perfect, and there are a couple of disadvantages to galvanised steel.

The first is that it’s one of the more expensive garden materials. While many materials for raised beds can be picked up affordably or even for free (for example, bricks or raw wood), galvanised steel costs a lot more upfront. However, when you consider how long it can last compared to other materials, it can work out better value for money. 

Galvanised beds are also not as easy to get hold of. While bricks can be picked up at construction sites, finding suppliers for galvanised steel can be tricky. Older galvanised steel pieces which can be sourced more easily may have already started to rust. 

Some metal beds also have very sharp edges, so this is worth bearing in mind if you’ve got excitable children or pets.

Finally, you will need to select the right soil for your galvanised steel beds. Soil which is very acidic can break down the zinc coating, so if you’re growing plants that require acidic soil, you’ll need a thick liner to prevent the soil from touching the sides. 

Common Misconceptions About Galvanised Steel Beds

There’s a few common misconceptions about galvanised steel beds, which is why lots of people choose not to use them. 

Myth 1: Zinc will leach into the soil

The main reason many people are reluctant to use galvanised steel is because they believe that zinc will leach into the soil, damaging their flowers and vegetables.

As galvanised steel is created by adding a layer of zinc to the surface of the metal, this belief does make sense!

Over time, a very small amount of zinc may get into your soil, but what many people forget is that plants actually require a small amount of zinc to survive. The amount that the soil and plants would absorb isn’t nearly enough to have a negative impact.

It’s also unlikely that the zinc would leach into the soil in the first place unless your soil was extremely acidic, as the acid would break down the coating. 

The best way to maintain the rust-resistance of galvanised steel beds is to avoid using very acidic soil. 

Some plants do require acidic soil, and if this is the case then you should use a liner (although many people choose to line their beds anyway). A thick liner will prevent the soil from touching the zinc coating. 

To prevent the zinc coating from breaking down, you should also avoid using chicken manure in your garden. While this can improve the quality of the soil, the acidity can break down the coating. 

Myth 2: Galvanised beds get very hot

If you’ve ever touched a metal item that’s been sitting in the sun for a few hours, you’ll know that metal conducts heat. 

But while galvanised metal beds may slightly warm the soil near the very edges, this isn’t going to be enough to damage your plants. Provided your plants have adequate water, the slight increase in soil temperature at the very edges of your beds shouldn’t make any difference. 

Myth 3: Galvanised metal beds need more water 

As metal conducts heat better than other materials, many people believe the soil will dry out quicker if the beds are made from metal, meaning more watering is required. . 

However, this isn’t to do with the material of the bed, and has more to do with raised beds themselves. The soil does naturally dry out faster, as there is a lot less of it compared to traditional in-ground beds. 

The key is to select a soil that retains water well. Gardeners with a large number of raised beds may also consider setting up an irrigation system. 

Other Materials for Raised Beds 

Galvanised steel isn’t the only material that can be used for raised beds. 

• Timber is affordable and easy to cut to size
• Raw wood adds a rustic aesthetic to your garden and can be picked up very cheaply
• Brick lasts for a very long time and is virtually maintenance-free. You can also easily incorporate curves into the design of your raised bed 
• Concrete blocks produce a smart and contemporary look, and will also help warm the soil quicker in the spring, leading to an earlier harvest. 

Materials to Avoid 

Whether you’re growing flowers or vegetables, there’s a couple of materials that should never be used for raised beds, as they contain chemicals that might harm your soil, plants and even your health. 

Pressure Treated Wood

Before 2004, chromated copper arsenate (CCA) was used as a wood preservative. It has since been discontinued, but older pressure-treated wood can still contain CCA. This is toxic and will leach into the soil.

As an alternative, alkaline copper quaternary (ACQ) is now used to preserve wood. While this is less toxic than CCA, it should still never be used if you are growing edible produce. 

MB Pallets 

Beds made from wooden pallets are quirky and attractive, but those stamped with an ‘MB’ should never be used. These contain methyl bromide which is harmful to human health. 

Railway Sleepers

Railway sleepers have often been coated with creosote, which can harm your skin. Not only is it harmful to humans, toxic chemicals can leach into the soil and damage your plants and insects too. 

Galvanised Steel Beds FAQ

How long do galvanised steel beds last? 

Galvanised steel is zinc-coated, which means it won’t corrode. As a result, galvanised steel beds can last up to 30 years, and they require very little maintenance. 

Do galvanised beds rust? 

Galvanisation requires coating metals that rust easily in a rust-resistant coating; in this instance, zinc. 

While galvanised beds may eventually rust over time, they are very unlikely to. Most metals begin to rust after just a few months exposure to water, while aluminium and zinc do not. 

Do you need to line galvanised garden beds? 

Many people choose to line the bottom of the bed, as well as the sides. This has a number of benefits, such as preventing weeds growing up from below, improving drainage and protecting against pests and rodents.

Commonly used liners include plastic sheets, cardboard, weed fabric, newspaper and leaves. 

It’s a myth that zinc will leach into the soil if you don’t use a liner, but you should still line the bed anyway. Small amounts of zinc may get into the soil, but this won’t damage your plants as it’s on such a small scale.

If you are growing produce that prefers acidic soil, such as carrots, cauliflower, cucumbers or tomatoes, you should line your galvanised steel bed. This is because the acid in the garden soil may eventually break down the zinc coating, reducing the lifespan of your beds. 

A thick plastic liner around the sides of your bed will prevent the acidic soil from making contact with the metal.

Is galvanised steel toxic to touch? 

Another common misbelief is that galvanised steel is toxic. However, in its finished form, zinc-coated steel items such as raised beds, buckets or tubs are not at all toxic to adults, children, plants or animals.