Raised garden beds have swayed many gardeners on their side for some apparent benefits. Other than the visual appeal, raised gardens will benefit from better quality soil, reduced interference of pests, and easier maintenance. Are you among the several gardeners thinking about making the fruitful switch to raised bed gardening? If so, the first thing to consider are options for construction materials.
It is important to use something that won’t wither with the next rainstorm and can be used year after year without losing its charm or its effectiveness.
So how long does a raised garden bed last? It really depends on the material of the raised bed; most gardeners choose cedar or redwood because of their natural resistance to rotting and infestations. In optimal conditions, they’ll last up to 10 to 20 years. However, longer-lasting materials are available as well. Besides durability, be sure to consider the material’s availability, budget, climate, and preferences to make the right choice.
Life Expectancy of Some Common Raised Bed Materials
|Material||Expected Life (Years)|
|Untreated Lumber||3 - 5|
|Naturally Rot-Resistant Lumber (e.g. Redwood, Cedar)||15 - 30|
|Untreated Pine||2 - 4|
|Pressure-treated Lumber||30 - 40|
|Galvanized Steel||20 - 40|
|HDPE Recycled Plastic||50|
Choosing The Best Material For a Raised Garden Bed
Durability is one consideration when picking the material for a raised bed garden, but there are other aspects as well. It’s also important to think along the lines of whether or not the material is locally available, construction cost, and the aesthetics of the final design.
While materials like stone, brick, and concrete may last a lifetime, they’ll cost much more. Besides, there’s the cost of hiring a mason since such materials don’t make a simple DIY project. Wood is cheaper and generally easier to work with, with the catch that it will eventually rot. It may need to be replaced once every 5 years. Naturally-rot-resistant wood or treated wood can last longer.
Let’s compare our options before we make a definitive decision.
The natural appeal of wood and its affordability makes it a popular choice among many gardeners. Sooner or later, all varieties of wood will rot. So the question is, what are the durable options? How does climate affect the longevity of wood?
Types of wood
Regular construction grade lumber without any treatment is the cheapest, and most readily available material found for raised beds. In suitable conditions, it should be able to handle 3 to 5 growing seasons before showing any signs of rotting. Naturally rot-resistant wood varieties, like cedar and redwood, can give up to 30 years of use but will cost 12 times more than untreated lumber.
Other types of hardwood are available as well. Pine is cheap and easy to work with. On the flip side, it barely offers any resistance to rotting or insects and will only last a couple of years. Oak holds up better against elements as compared to pine but is very expensive. Furthermore, it’s hard to work with, especially when it’s dry and rarely available in large quantities in stores.
Composite wood is growing as a popular choice for outdoor landscaping. The material is a blend of wood and plastic resins, making them much more durable than untreated lumber. However, according to the University of Georgia Extension, they are prone to cracking, mildew, discoloration and degradation in much the same way as regular wood.
How does climate affect wooden raised beds?
Do consider local climate when choosing a suitable wood variety for a raised garden bed. Cedar lasts the longest in dry climates. In humid climates, the better option is to skip wood and go for a different material. If the wood doesn’t get a chance to dry completely, it will rot much faster than its average life expectancy.
In addition to climate, the watering pattern also affects a raised bed’s durability. For those gardeners who are planting water-intensive crops in a raised bed, a wooden raised bed won’t last very long. If you’re wondering whether raised bed gardening suits a certain climate, read our post Are Raised Garden Beds Better than In-Ground Garden Beds? to learn more.
Types of Masonry Materials
Gardeners typically include stone, concrete, bricks, pavers, cement and similar construction materials in this category. Of these options, cement is the most readily available and cheap. It is typically not difficult to find cement blocks that work excellently for the purpose and are available at nominal prices.
According to the University of Missouri Extension, a gardener can build a 2 feet tall raised bed by stacking cement blocks or stones without using any mortar. Taller walls will need to be mortared to prevent collapse.
As for the durability, it is not likely to find rotting or insects chewing away the garden bed. They’ll literally last as long as one will be gardening. Although purchasing cinder blocks, bricks, or pavers from garden centers or Home Depot might cost more than lumber, there is a cheaper option. Pick leftover or used material from a construction site (do ask the site owner first in order to avoid trouble!).
How does climate affect masonry raised beds?
Raised beds made out of stone and other masonry materials are excellent options for colder climates. The stone wall will heat up the raised bed soil much faster than the surrounding soil. They make it easier to plant earlier in the spring and extend the growing season for warm-weather crops. As for warmer climates, avoid choosing masonry materials for raised beds, since they may increase the soil temperature beyond the suitable range for many plants.
For extremely cold climates where the ground freezes frequently during the winter, masonry material may be prone to cracking so keep that in mind when choosing your material.
If wood isn’t ideal for your particular climate and stone is too heavy to use, then plastic offers a perfect solution. It’s an excellent alternative to wood since it holds up well against rotting and infestations. Furthermore, unlike wood, it’s the lightest and easiest material to build raised beds. Also, it’s portable, so if you plan on moving your raised bed to a sunnier spot, just disassemble the entire thing and set it up at a different place!
Types of plastic
Recycled plastic is the most commonly available variety available in this category. They come in a range of different colors. Synthetic lumber is a popular choice since it gives the appearance of natural wood. If the original color is not ideal, then the color can be changed by applying a coat or two of heat-reflective paint.
For a raised garden bed that won’t need to be replaced in half a century, go for HDPE plastic. This recycled plastic isn’t just long-lasting, but also stable – it will not leak any toxic chemicals into the vegetable garden.
How does climate affect plastic raised beds?
Plastic raised beds offer good insulation to plants against sudden temperature changes. The thinner varieties, however, will eventually crack with prolonged sun exposure or excessive moisture.
Are raised bed kits a good option?
For those gardeners who are not up for a major DIY project, ready-to-assemble raised bed kits will make life easier. They’re readily available at local garden centers and online stores, some at very attractive prices too. However, do consider the construction material and the company background to select a raised bed that will last.
This Raised Bed Garden Kit seems to be one of the more popular choices on Amazon, although we haven’t tried this out ourselves yet to verify.
The fear of the Lord prolongs life, but the years of the wicked will be short.Proverbs 10:27
Tips to Make a Raised Garden Bed Last Longer
In order to extend the life of a wooden raised beds, here are a couple of things that can help:
Freezing water in winters can cause beds to pop from the corners. Using corner brackets can help secure regular untreated lumber beds from cracking during wintertime.
Applying an oil-based stain, or latex paint on wood can prevent it from rotting. Latex paint will also keep out most insects. If chemicals are a concern, there are eco-safe varieties available, however in either case it will not harm your plants or you.
Are Plastic Liners Any Good?
Lining raised beds with plastic has its advantages. It keeps out pests, insulates the plants against extreme temperatures, and prevents toxic chemicals from pressure-treated wood from leaching into the soil.
However, as far as the durability of wood is concerned, plastic liners are NOT helpful. It’s a common misconception that lining a wooden raised bed with plastic will prevent rotting and increase its life. On the contrary, they’ll trap moisture between wood and plastic to speed up rotting, especially when the weather is hot and humid. If rotting is a concern in your particular area, use stone, concrete, or plastic raised beds instead of wooden ones.
A bundle of options are out there for setting up a raised garden bed. Most of them will last several years before rotting, cracking, or warping. Pick a material that will hold up well against the elements, construct it wisely, fill it up with good quality potting soil, and get planting! There’s no reason why gardeners can’t enjoy multiple successful growing seasons in a row!
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