How to Seal and Protect a Wood Raised Bed

Make Sure Your Wood Raised Garden Beds Last as Long as Possible

Building your own wood raised beds is often the most cost-effective way to get set up and growing.

My favorite type of wood to use is untreated cedar. It's more expensive than something like pine, but it will last a lot longer. I try to avoid treated wood because they used to use some really toxic stuff to preserve each board. They say they're not using anything bad on wood anymore, but I like to play it safe when it comes to the space that will grow my food, you know?

The problem is, without being treated, wood can degrade quickly when it's next to wet soil and exposed to the elements. Rather than buying pre-treated boards, I prefer to add a wood preservative to untreated boards to increase their expected lifespan in the garden. There are great eco-friendly, mineral-based treatments out there that will protect your wood—no harsh chemicals needed.

How Do Mineral-Based Wood Preservatives Work?

The minerals in the wood treatment penetrate the wood fibers to prevent them from absorbing water and starting to degrade over time. This offers long-lasting protection from sun and water. The treatment will not wear off, peel, or fade—it's basically maintenance-free protection for your wood raised beds.

You can treat both the inside and outside of your raised bed, but it's especially important to treat the interior of the bed, where damp soil will frequently be pressed up against the wood surface.

One thing to be aware of is that the minerals add a silvery patina to the wood. I personally prefer the way pine boards look after they've been treated because it removes some of the yellowy tint.

I've used mineral-based treatments for years, but what really showed me how effective they are for untreated cedar were these in-ground wood steps used in a design in Houston. I knew the steps would get a lot of wear and tear, so I treated them. Over five years later, they're holding up great, even with all of Houston's hot and humid weather.

The best time to treat your wood is before you build your raised beds so that you can make sure to seal every little area.

Do I Have to Seal a Wood Raised Bed?

Using an eco-friendly wood treatment is a great way to increase your confidence that your raised beds will last a long time. I recommend at the very least coating your lumber in linseed oil or beeswax to preserve them for the long haul.

Some gardeners use lining between the interior of their raised bed and soil to protect the wood. Even with the lining, you'll get seepage of water that will penetrate that wood and linger. That's why I recommend using a lining with a wood preservative instead of in lieu of.

As I said, treating your wood with a mineral-based preservative will add a silvery patina when it dries. The raised beds pictured below were just treated with Eco Restore Wood Treatment. If you don't want the color of your brand-new bed to change, you can always treat the interior of the bed and leave the exterior untreated. That will still give you a few more years with a more durable wood like cedar. For a lumber like pine, which is not as resistant to rot and decay, it's best to treat both the inside and the outside.

My Top Recommended Wood Preservatives

There are several products I've used for years in my own garden and in hundreds of clients' gardens. They're safe to use around pets and, of course, plants. They don't leave any harmful residues in the soil, so you don't have to worry at all about these products coming into direct contact with your garden soil.

(Head's up: this post contains Amazon affiliated links, which means I earn a small profit if you purchase my recommendations.)

Valhalla Wood Preservative

Valhalla Wood Preservative is eco-friendly and non-toxic. It costs $75 for five gallons, which is enough to seal 750 to 1,000 square feet of surface area (basically enough to coat a whole wood deck).

Eco Wood Treatment

Eco Wood Treatment is made from naturally occurring plant and mineral extracts. A 2-ounce packet costs $30. That makes 1 gallon of preservative and covers 150 square feet.

One gallon of wood preservative should be more than enough to coat the inside and outside of a 4ft x 8ft x 2ft raised bed.

Hope's 100% Pure Tung Oil

Hope's tung oil is made of seeds from tung trees, so it's a natural, food-safe wood finish. You can get 16 oz. for about $20. Unlike the powder-based treatments, this is an oil that you wipe on using an old rag, sponge, or paint brush, and then give it time to cure at room temperature.

Supplies to Seal Wood Raised Bed

This is a pretty simple DIY project, so you only need three things:

• eco-friendly wood preservative
• paintbrush or roller brush (or paint sprayer)
• 5-gallon bucket from hardware store

Steps to Seal Wood Raised Bed

Step One: Mix

The mineral powder has to be mixed with water before applied. Use your bucket to mix however many gallons of water the product you've purchased calls for. The result will have a milk-like appearance.

If you're treating several raised beds, you might want to measure out the powder and mix one portion at a time. That way, you know exactly how much mixture you have to use for each raised bed.

Note: When wet, the mixture will be slightly acidic, so avoid getting it on your skin or in your eyes.

Step Two: Paint

Use your brush or roller to paint the treatment onto the wood. Make sure to coat each board thoroughly, especially the cut edges. Covering every single grain of wood will make this treatment as effective as possible.

If you accidentally get the mixture on your clothes or something else, you can clean it up with soap and water.

You'll probably notice the slight change in color as the treatment penetrates the wood and dries. That's your sign it's working!

Step Three: Let Dry

This mixture actually dries pretty quickly, but it's still a good idea to give it time to penetrate the wood once you've painted it on. If you're treating wood boards before constructing a raised bed, wait at least 24 hours before busting out the power tools. If your raised bed is already built, wait at least 24 hours before filling the bed with soil.

A single application is enough to protect your wood, but if you have mixture leftover, you can always do another coat, especially on the inside of your raised bed.

Make Sure Your Wood Raised Beds Last a Decade or More

Wood is an affordable way to get started in the garden, and now we can add more durability and sustainability to an already great option for your raised bed material. Treating your beds with wood preservative is such an easy way to add peace of mind that your investment is going to last much longer.

Thanks for being here and making gardening ordinary again!