The Best Raised Garden Bed Materials - For All Climates

By Sabina Pariser 

Raised garden beds are an attractive and accessible addition to any outdoor space. One of the most important decisions you can make when preparing to build raised beds for your garden is deciding which material is best for you!  So many factors can go into this assessment, whether it be budget constraints, square footage, or aesthetics. Another significant thing to acknowledge is your local climate conditions. Do you live in a humid environment? How about a dry and arid place? Discovering the characteristics of the climate you reside in will play a crucial role in determining which material is best for your raised garden bed.

It is easy to determine what climate zone you live in by utilizing helpful resources on the internet. Climate zones are categorized by temperature, humidity, precipitation, and the timing of the seasons. Globally, these zones are divided into horizontal spaces that move from east to west, including all areas between the South Pole and the North Pole. The international climate zones are typically separated into four categories: polar, temperate, tropical, and subtropical. The global map from Meteoblue is a great resource in identifying global climate zones. Furthermore, if you are a gardener residing in North America, you can access the National Gardening Association’s Plant Hardiness Zone Map, which will give you a detailed description of your climate zone. Just enter your zip code to find out more about the climate zone in your area.

In my garden, I have eight raised beds dedicated to food production. I am hoping to add an additional twelve beds to our yard to increase our yields. Right now, I have untreated cedar beds which are aesthetically pleasing and practical to use. However, the Pacific Northwest is typically a wet province with an average rainfall of about forty-three inches per year.  Still, the Pacific Northwest continues to experience increasingly warm and dry summer months. My wooden beds must withstand an array of climate fluctuations, and I worry about the longevity of my cedar vegetable beds. For this reason, I am exploring other long-lasting material options for my future raised beds.

Below, I have listed three options that are ideal for long-lasting raised bed materials based on individual climate types. I hope this research is helpful for other gardeners who are doing long-term planning for their food production and planting needs.  

Wet, damp, or humid climates:

Best - Galvanized steel raised beds are aesthetically attractive with a modern, sleek appearance. They are also ideal when looking for a garden bed that is well accustomed to wet or humid climate conditions. Unlike wood, steel will not decay or rot in wet conditions. To prevent your raised beds from rusting, always source galvanized steel which has a protective coating to avoid corrosion.

Better - Composite wood raised beds are made from a blend of wood fiber and recycled polypropylene. Composite wood is another great option when considering a long-lasting raised bed for a wet or humid environment. The textured blend is considered a minimal maintenance option because the boards will not rot, warp, or decay as quickly as traditional wood raised beds.

Image: Compostite wood raised bed

Good - Brick is another appropriate long-lasting material to consider in a wet or humid climate. Brick is a resilient material that does not require regular repairs to maintain durability. Brick is naturally resistant to pests and is easy to customize based on your needs. However, due to its porous nature, brick walls can be prone to water penetration which will hold in moisture (through a process known as ingression), especially during sustained rainy weather. However, brick is not as sensitive to moisture as wood, which makes it a good option for damp or humid climate conditions.

Cold climates:

Best - Brick or natural stone material has higher thermal mass than other long-lasting raised bed options, making it the ultimate candidate for cold climate circumstances. Thermal mass can be described as the ability of a material to absorb and store heat. This makes brick and natural stone an excellent temperature regulator which can help extend your growing season and insulate your soil during transitional months.

Image: Brick raised bed with leeks growing

Better - Galvanized metal beds are another fantastic option for colder climate regions because they are exceptionally durable and provide natural protection during extreme weather conditions. If you live in an area with chilly conditions, you can think about selecting a darker color for your metal raised bed, which will help absorb heat and warm soil temperatures.

Good - Natural wood raised beds are a suitable option for cold and dry weather conditions. As stated before, wood is sensitive to wet conditions and can decay over time. However, for dry and frigid conditions, natural wood material insulates heat well, which can help to extend your growing season in the spring. When sourcing natural wood materials, be sure to purchase untreated wood which is free of unwanted chemicals. If you are looking for a budget-friendly option, you can source untreated pine or oak. If you are looking for a more robust wood substance, I suggest cedar, cypress, or redwood.

Image: An alternative option is recycled plastic raised beds like the main one in the image above which are chemically inert, last a long time, and help absorb and retain heat.

Hot Climates:

Best - Galvanized metal is a superb option for hot and arid climates. Steel beds are ideal for water retention as the water does not egress from the garden bed as it would with a traditional wooden raised bed. Also, galvanized steel has a natural reflective quality to it, which allows for the soil in the beds to stay at an even temperature throughout the day.

Better - Wood composite is another decent option when gardening in warmer climates. Wood composite is not degraded by sunlight and will not fade excessively over time. The material is resistant to bugs and other pests. Lastly, it is not as sensitive to water loss as traditional wooden beds.

Good - Wooden raised beds are another excellent option for gardeners looking for long-lasting material for warmer climate conditions. Wood has less thermal mass than brick or stone and will function as a beneficial insulator during transitional seasons without retaining excessive heat. Wooden raised beds can lose water in hotter climates (through a procession called egression). To help with water retention, you can add grass clippings or organic straw hay to the top layer of your garden bed.

After careful research, I have decided to move forward with using galvanized metal beds for my garden. I think the addition of modern steel framing will contrast nicely with the rustic cedar beds that currently reside in my yard. I anticipate it will add depth and beauty to my suburban plot. Also, I am excited about the water retention capabilities of steel metal beds. While we do live in a wet climate, we tend to have very dry and sweltering summer months. In the past, I have had to add top layers of grass and/or organic straw hay to my wooden beds to help with water retention. I am hoping to see a notable difference in water retention and soil temperature stability with my new galvanized steel raised beds.

I hope you have found this information helpful. As you can see, galvanized metal is one of the most resilient and sturdy materials you can use for your garden bed. They are typically quite easy to place in the garden, since you do not need to build the beds, like you would if you used natural stone, brick, or wooden raised beds. Secondly, brick and natural stone can be a great option because they have superb natural insulating abilities and can be an artistically pleasing addition to your garden. Choosing a robust organic wooden material, such as cedar, for your raised bed can be a great addition to your garden and will allow you to extend your growing season year after year. 

Some thoughts from Huw

I was surprised to see how suitable galvanised metal raised beds are for hot climates. I have heard many times from people wondering if they will heat up the soil too much, almost cooking it potentially, yet this simply is not the case. There are also a few fantastic YouTube gardeners growing successfully in hot climates in metal beds. Whilst this article is focusing on the absolute best material for each climate, don't let it put you off making raised beds if you have other materials available to you. The most important element is to be able to grow your own food and the majority of my beds are wooden even if it isn't going to last the longest it is the most accessible for me, and replacing boards of wood for beds is a simple process.