As a general rule the best type of wood for a garden project is either a treated or hard wood. You need to consider the type of project, if the wood will contact the ground than you should choose a treated lumber to help avoid wood rot. The exception to this rule is garden beds which have vegetables planted in them. It is best to avoid treated wood in vegetable beds because the chemicals used to treat the wood could seep into the soil and effect the quality of the food grown. In this case try to find a good hard wood like cedar for the beds.
What wood lasts the longest outdoors?
- Generally speaking, any hard wood will stand up to weather longer than soft wood. Some examples of good hardwoods to use are
- Cedar (also known for being bug resistant)
- Oak
- Walnut
- Treated Lumber
- Composite wood (can be a more affordable option)
- Redwood
- Cypress
- Teak
- Yew
- Mahogany
When looking to extend the life of wood outdoors it is best to use a paint or sealant. Any wood needs to be cared for to get the maximum life span out of it.
Which lumber is ideal for exterior projects?
The woods listed above are the best for exterior projects.
This is because you are looking for a strong weather, rot, and bug resistant wood. However, when looking at your exterior projects you need to take cost and structure into account. For instance, a garden bed has different wood needs than a deck. Let’s look at a garden bed example. We can ask ourselves how long do we intend to keep the garden bed? If you plan to move the garden beds or replace them after a few years than there is no need to use a more expensive wood such as cedar.
A composite or softer wood such as pine will work just fine and be much cheaper. However, if you intend to keep the garden beds in the same location for more than five years then a thick cedar board will be better. You will spend more up front but the rot and bug resistance in addition to the hard wood will keep that garden bed sturdy and looking good for a very long time. You can learn more about raised garden beds here.
Does pressure-treated wood prevent rot? Good for Raised Beds
As a general rule pressure treated wood does not prevent rot. What pressure treating wood does do is make the wood water resistant. The cause of most wood rot is penetration of water into the grain of the wood. By pressure treating the wood you reduce the ability of water to penetrate the woods surface. However, temperature fluctuations will cause micro fluctuations in the woods allowing water to seep in.
Although there is no way to fully prevent water from soaking into wood some additional steps can be taken. Adding a coat of paint or sealer onto the treated lumber will add to its water resistance. Remember to add paint or sealant maintenance to your yearly calendar. I recommend inspecting the wood every spring to see if any repairs or repaints are needed.
Best rot resistant lumber for garden project plans
Rot resistance in wood comes a a natural produced compound called extractives. These are created by the tree over time as a way of protecting itself from rot and insect infestations. There are some trees that produce more extractives overtime and are considered to be the best rot resistant varieties.
Before we go over varieties, we need to discuss the type of wood cut best for rot resistance. The heartwood otherwise known as the center most part of the tree is believed to contain the most extractives causing it to have the most rot resistance. By looking at the grain pattern on the end of the wood cut you can often determine if the cut came from the heartwood. If you are looking for the most rot resistant lumber, start with the cut then look at variety options.
For the 10 most common rot resistant woods used in garden projects with cost and bug resistance see chart below.
| WOOD VARIETY | Average Cost PER 6 FT Board | NATURAL BUG RESISTANCE |
| Cedar | $20.58 | Cedar naturally repels mosquitoes, woodworms and some varieties of moths. |
| Walnut | $54.08 | Walnut is a very hard wood that repels most bugs including termites. |
| Oak | $27.21 | No special resistances |
| Redwood | $28.50 | Although one of the softer woods on this list it is very Termite resistant |
| Cypress | $31.37 | Cypress is not a great insect resistant wood due to its ability to retain moisture. However with a good sealant it will hold up well over time. |
| Treated Lumber | $9.85 | Termite resistant Treated Lumber is one of the best anti bug woods available. |
| Teak | $27.80 | Teak is both Termite resistant and produces an oil that repels mosquitoes and other burrowing insects. |
| Yew | $34.00 | Wormwood resistant. Yew is generally not touched by insect due to its toxic sap. |
| Mahogany | $40.53 | Mahogany is very bug resistant due to its very dense properties. |
| Composite Board | $21.67 | Termite resistant Most insects will avoid composite board if a sealer is applied. |
For organic gardeners that would like to seal there wood project in a more natural way. Linseed Oil and Tung Oil are great natural ways to help prevent wood rot and bug infestation. They’re often used to seal beehives due to their level of safety to insect while still providing protection.
Cheapest wood for raised garden beds | Common woods used in gardening project
As shown in our price chart treated wood is the cheapest option for raised beds. Its cheaper than cedar wood well still holding up well to moist bed soil. Pressure-treated wood holds well to outdoor environments. Keep in mind chemicals are used in Pressure-treated wood and may not be the best option for vegetable garden projects.
Consider looking around and taking all the things discussed in this article into consideration when planning out your outdoor projects. If your project only needs to last a few years you may want to consider a cheaper option of wood. Opposite of that if you plan to use your wood project for many years try to budget for a harder more rot resistant wood like the Mahogany or Walnut. Also consider insects in your area. Some areas are more prone to termites or mosquitoes if you find that to be the case you may want to chose a wood that helps address that issue.
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