Best Wood for Raised Bed Planters: Options

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Updated 19 October 2026 | Author: Editorial team, homelycapers.com

The best wood for raised bed planters is a decay-resistant species, such as cedar or redwood, because those woods hold up when they stay in damp soil. University extension pages also list black locust, black cherry, oak and Osage orange as decay-resistant, and they describe pressure-treated lumber as a workable option when it is the right type and is lined or sealed. Cheaper untreated softwood is possible but does not appear on the decay-resistant list. This guide compares the options and explains the safety points extension pages raise about treated wood.

Quick answer

Pick a decay-resistant species if you can afford it. The University of Maryland Extension lists cedar, black cherry, oak, black locust, Osage orange and redwood. Illinois Extension calls untreated cedar an excellent choice but notes it can be very expensive.
Pressure-treated lumber is the common residential option. The Maryland page says micronized copper azole (MCA) is the most widely available pressure-treated lumber for residential use.
Older arsenic-treated wood is the one to avoid. Chromated copper arsenate (CCA) was discontinued for outdoor residential use in 2004, according to the Maryland and Illinois pages.
Line or seal the wood. Maryland recommends exterior latex paint or a preservative for the wood, and a heavy plastic liner on the inside of the frame, with drainage holes or a liner on the sides only.

What the wood has to do

A raised bed frame does three jobs. It holds the soil in shape, it keeps the bed level, and it stays in contact with wet soil for years. The third job is the one that separates the options. Wood that rots in a few seasons turns a good bed into a repair job, and the extension pages treat decay resistance as the first thing to check.

Iowa State University Extension describes the walls of a permanent bed as something that can be made from several materials. It lists decay-resistant wood such as cedar or redwood, along with landscaping timbers, composite lumber, PVC boards, metal, concrete blocks, rock or brick. This guide focuses on wood, but the same trade-offs apply to those alternatives: durability, cost, and what the material may release into the soil.

The wood options side by side

Option	What the extension pages say	Main trade-off
Cedar or redwood	Both appear on the decay-resistant lists in the Maryland and Iowa State pages	Illinois says untreated cedar can be very expensive
Black locust, black cherry, oak, Osage orange	Listed as decay-resistant in the Maryland page	The pages do not say where each species is easy to find
Untreated spruce, pine or fir (SPF)	Maryland says untreated SPF is less expensive than pressure-treated wood	It is not on the decay-resistant list the Maryland page gives
Pressure-treated, MCA	Maryland calls it the most widely available pressure-treated lumber for residential use	It adds a small amount of copper to the soil within 1 inch of the edge, according to Oregon State research cited by Maryland
Older CCA-treated lumber	Discontinued for outdoor residential use in 2004	Avoid it; the pages do not describe a simple test for old stock
Galvanized metal	Iowa State says it may leach heavy metals such as lead or cadmium into the soil	The concern is the surrounding soil, so a barrier or a soil test is the step the pages point to

The table makes one point clear. Decay resistance and chemical safety are separate questions, and a board can be strong on one and weaker on the other. Cedar and redwood avoid the chemistry question but cost more. Pressure-treated lumber is cheaper and easier to find but raises the chemistry question, which is where the extension research matters.

Pressure-treated lumber and what the research found

Pressure-treated wood is the option most gardeners ask about, and the extension pages give a clear answer. The Oregon State University Extension Ask Expert answer on pressure-treated raised-bed lumber says the main concern has been arsenic in CCA-treated wood. That is why the 2004 change matters. The Maryland page reports the Oregon State research on newer lumber. It found that MCA pressure-treated lumber increases soil copper by a minor amount, but only within 1 inch of the raised bed edge. The same study found no increase in copper in plants grown in beds made with that lumber.

That finding points to a measured response rather than a ban. The increase was limited to the soil next to the edge, and the study found none in the plants. If the question still bothers you, the Maryland page offers two choices: paint or stain the wood before you build or plant, or use an alternative material such as stones or bricks.

Some older wood is the bigger concern. The Illinois Extension blog notes that lumber treated with arsenic was phased out in 2004 and that lumber is now treated with copper and approved for growing food. It adds the advice to wash vegetables well. If you are using salvaged lumber, the age of the wood is a reason to ask questions before you build, because the pages do not give a way to identify CCA-treated stock by sight.

Liners, paint and drainage

Raised beds can be finished in a few ways, and the extension pages describe three that work together.

Paint or stain the outside and the cut ends. The Maryland page recommends coating the wood with exterior latex paint, or treating it with a preservative such as a semi-transparent oil-based stain. The Maryland page presents these steps as ways to handle treated wood and limit soil contact with it.

Line the inside of the frame. The Maryland page recommends a heavy-duty plastic liner inside the frame before you fill the bed. It advises either drilling drainage holes in the liner or leaving the bottom unlined and lining only the sides, so water can still drain out of the bed. The Iowa State guidance says that treated wood may need to be lined with woven geotextile fabric, which lets water drain through while keeping soil and roots away from the wood.

Plan the drainage. The reason for a bed is drainage. The Iowa State guidance says a properly prepared raised bed increases drainage and promotes plant growth. A liner that seals the bottom of the frame undoes that benefit, so the choice between lining the sides only and using drainage holes matters.

Size and height

The wood you choose also sets the size of the bed. The University of Maryland Extension describes raised beds as usually 2 to 4 feet across and 2 to 12 inches tall. Illinois Extension recommends building no wider than four feet, because a gardener cannot reach the middle of a wider bed comfortably, and it recommends a height of 12 to 24 inches. Iowa State says beds that can be reached from both sides can be 3 to 4 feet wide.

Board height is easy to plan. Iowa State notes that 11 inches is a common height, because it equals two 2×6 boards. A 2×6 board measures about 1.5 inches by 5.5 inches, so two boards stacked on edge give 5.5 x 2 is 11 inches of wall height. The walls are not the only cost, so measure the bed you actually want before you buy lumber.

For a bed that is 4 feet wide and 8 feet long with 11-inch walls, the soil volume is the next number to know. Eleven inches is about 0.92 feet, so 4 x 8 x 0.92 is 29.44 cubic feet of soil to fill the frame. That is the figure to compare with your soil order, and it is smaller than the 32 cubic feet of a 1-foot-deep bed of the same footprint.

Common mistakes the sources warn about

Using old or unknown lumber. The 2004 change in CCA use is the reason the pages flag older stock. If you cannot tell what the wood was treated with, the sources do not give a safe way to decide, so choose a labeled product for the bed.

Building a bed too wide to reach. Illinois and Iowa State both set width limits that come from reach, not from wood strength. A narrow bed is easier to plant and weed, and it puts every plant within arm’s reach.

Forgetting the liner or drainage holes. A liner with no drainage can hold water in the bottom of the bed. Either drill holes in the liner or line only the sides, as Maryland recommends.

Using galvanized metal without a barrier. Iowa State says galvanized metal may leach heavy metals into the soil, and it lists a barrier between the wall and the soil as a step to consider.

Ignoring the edge zone. The Oregon State research cited by Maryland found the copper increase only within 1 inch of the edge. Knowing where that zone is makes the research easier to apply to your own bed.

How we chose

We started from the choice a gardener makes at the lumber yard: which wood to build a planter from. We looked for university extension pages that compare wood types or explain treated wood, and we used the Maryland, Iowa State, Illinois and Oregon State pages because they cover the same questions from different angles. We kept only pages we could open and read in full, and we checked each quoted sentence against the saved page text before we used it.

We did not rank wood by cost, because the pages do not give current prices and prices change by region. We did not name a product or a store.

What we could not verify

The pages we opened do not give a lifespan in years for cedar, redwood, pressure-treated lumber or any other wood in a raised bed.
The sources do not say which decay-resistant species is easiest to buy in your area, or what each one costs.
The pages do not describe a field test to tell CCA-treated wood from newer treated wood.
The Oregon State research described on the Maryland page is one study. We did not find a second study that confirms the copper result for every soil.
The pages we opened do not cover composite lumber, plastic boards or stone in detail, so this guide does not compare those materials on cost or lifespan.
The pages do not say how often a painted or stained frame needs to be refinished.

FAQ

Is cedar the best wood for a raised bed?

Cedar is one of the decay-resistant choices in the extension pages, along with redwood and several hardwoods. Illinois Extension calls untreated cedar an excellent choice for rot resistance and durability, but also notes it can be very expensive. The pages do not rank the species against each other.

Is pressure-treated wood safe for growing vegetables?

The Oregon State and Maryland pages both address this. The concern has centered on arsenic in old CCA-treated wood, which was discontinued for residential use in 2004. The newer MCA-treated lumber that Maryland describes was studied, and the copper increase found was small and limited to the area within 1 inch of the edge. Maryland still suggests painting or staining the wood if you are concerned.

Do I need to line a wooden raised bed?

Maryland recommends a heavy-duty plastic liner on the inside of the frame, with drainage holes or a liner on the sides only. Iowa State says treated wood may need a lining of woven geotextile fabric that lets water drain through. Either approach separates the soil from the wood while keeping drainage.

How tall should a wooden raised bed be?

Maryland describes raised beds as usually 2 to 12 inches tall. Illinois recommends 12 to 24 inches, and Iowa State notes 11 inches as a common height that matches two 2×6 boards. Higher beds are easier to work from, but they take more soil to fill.

Can I use old lumber for a raised bed?

Be careful. The sources say CCA-treated lumber was discontinued for residential use in 2004, and they do not give a visual test to identify older treated wood. If the age or treatment of the wood is unknown, choose lumber with a clear label rather than relying on the look of the boards.

Bottom line

Build with a decay-resistant species such as cedar or redwood when the budget allows, use labeled pressure-treated lumber when it does not, and line the frame or paint the wood as the extension pages recommend, keeping the bed no wider than an arm’s reach.

Sources

University of Maryland Extension, “Growing Vegetables in Raised Beds”: decay-resistant species, MCA and CCA history, paint, liners and bed dimensions.
Oregon State University Extension, “Raised bed lumber, pressure treated safe?”: the arsenic concern with CCA-treated wood.
Iowa State University Extension, “Creating Raised Bed Planters”: decay-resistant wall materials, treated wood with liners, galvanized metal and bed widths.
University of Illinois Extension, “Raised Beds: Benefits and Considerations”: untreated cedar, copper-treated lumber, the 2004 phase-out and height and width advice.

Best Wood for Raised Bed Planters: Cedar, Treated and What to Avoid