Whenever you are looking to build raised garden beds, the question of materials is typically the first that comes up. It is easier, and cheaper, to use what is available and on hand. What if that material is left over from a deck project? In this case, I was wondering if I could use leftover Trex from a deck project to build out my raised garden beds.
Can you use Trex for raised garden beds?
Composite decking materials, including Trex, are excellent for use in raised garden bed projects. Though their cost is higher than traditional wood products, and they are more prone to bowing and bending, it is a great option for a single season if you already have them on hand.
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Using Composite Wood vs Real Wood for Raised Garden Beds
Trex is just a brand name composite decking. It looks good and stays looking good. Because it is a composite, it won’t rot, splinter or fade like real wood does. Bugs don’t burrow in it and the sun doesn’t degrade it.
The disadvantages to using Trex is that it will require more support to keep it’s shape. Trex isn’t as dense as wood and it is designed for decking, where there is lots of support via joists.
In a vertical application, such as for a raised bed, you’ll need to ensure it has adequate support for each of the sides in order to maintain shape.
Real wood, on the other hand, will maintain shape and it’s natural rigidity means that you don’t need as many supports in order for it to keep shape and hold back the soil in your beds.
Because real wood does deteriorate over time, every few years you’ll need to evaluate and replace boards when needed. This can be viewed as a good thing or a bad thing depending on the way you look at it.
| Trex | Real Wood | |
| Fade Resistant | Yes | No |
| Rot Resistant | Yes | No |
| All Natural | No | Yes |
| Pest Resistant | Yes | No |
| Easy to Install | Yes | Yes |
| Green Choice | Yes | No |
Safety of Using Composite for Vegetable Gardens
According to the Sierra Club, composite lumber, like Trex, is a safe option for garden beds. The material from which it is made, polypropylene, is used for many applications.
In fact, the USDA allows composite lumber for beds and fencing on farms seeking certification as “organic”.
When looking at options for your vegetable garden, you should do your research on material types and make a decision that you are comfortable with.
Installation Tips
Before you get started with installing your raised garden bed, whether using Trex or some other material, you’ll want to keep a few things in mind.
1. Have a plan.
Sketch out the design of your garden area. Whether you plan on having one bed or many, knowing the size and number of beds you need will help ensure your materials list is accurate.
2. Plan for water.
We all know that water is crucial to the growing cycle. It makes sense to plan for water before you install your beds. Doing so, gives you more options than figuring out you need a watering plan as an afterthought.
While you can water your garden beds by hand, consider whether an automated water system makes more sense. In most cases, having it done for you means you have more flexibility to spend time on other things.
As an added bonus, you won’t have to worry about the garden if you decide to go out of town for the weekend.
3. Establish a plan for weeds.
Weeds are a fact of life when it comes to gardening, and weeds in raised beds are no exception.
If you are installing the garden bed on dirt, as most will, you may want to consider adding some kind of weed barrier. This simple step may help to save you time season after season by limiting the number of weeds present in your garden.
Of course, it won’t eliminate all weeds, but it sure might help.
Once you have a plan in place, it’s time to install your raised bed. Here is a helpful video I found for installing and filling a raised garden bed made out of Trex.
Other Raised Bed Materials
When trying to decide if using a composite lumber, like Trex, is the way to go for your raised garden bed, keep in mind that there are other material options available as well.
| Material | Price | Longevity |
| Untreated Wood | $ | 2 – 5 Years |
| Composite Lumber | $$ | 25 – 30 years |
| Galvanized Metal | $$$ | 30 – 60 years |
| Concrete Block | $$ | Lifetime |
Untreated Wood
Untreated wood is the old tried and true standard for raised beds. It’s cheap, it’s readily available and it is easy to throw together.
You can even get creative and paint the outside of the wood if you like which can both add color and help protect the outer surface of the wood.
Lining the inside of the raised bed will help the untreated wood surface to last longer but, this material breaks down the fastest. Of course, that makes sense when you think about it. All natural materials naturally break down.
Untreated wood is a great option if you are just experimenting with the idea of doing a raised bed garden system and want to get started right away on a budget.
If you do decide raised bed gardening is right for you, you can always move to a different solution in the future.
Galvanized Metal
Galvanized metal can be another great option for raised beds. While it is more expensive than wood and, depending on the price of metal in your area, likely more expensive than composite, it’s a great option.
Galvanized metal is going to be rust resistant and strong. The metal sides will hold up probably for your lifetime. In fact, you are more likely to need to replace the wood corners before you have to replace the side panels.
I hadn’t even thought about galvanized metal as an option until I stumbled upon an article over at wholefully.com. I highly recommend you check it out.
The cover in detail why they chose to go with galvanized metal as well as detailed instructions on assembly.
Concrete Block
Concrete blocks are a nice, permanent yet movable way to add a raised bed to your garden. They are cheap and relatively easy to install as well.
You can adjust the height of your bed just by adding or removing bricks. One other benefit is that you won’t need wood bracing. The concrete blocks are rigid enough to hold the weight of the soil.
This is an excellent video on how to build a raised bed out of cinderblock.