Cedar and redwood last longest without treatment
Cedar and redwood are the top choices for raised beds because they resist rot naturally. Both contain oils that repel insects and decay, so they hold up for 10 to 15 years even in wet soil without any sealant or paint. Cedar is more widely available and costs less than redwood. Redwood is denser and slightly more durable, but both will eventually split and weather to gray as they age — that does not mean they have failed.
If you choose cedar or redwood, buy heartwood (the darker inner wood), not sapwood (the pale outer ring). Sapwood rots quickly. You will pay more for heartwood, but it lasts twice as long. Expect to spend $1 to $3 per linear foot for cedar boards, depending on thickness and local supply.
Neither wood needs treatment, but you can stain or seal them if you want to slow graying. Do not use pressure-treated sealant on beds where you grow food — the chemicals can leach into soil over time.
Key Takeaways
- Cedar and redwood heartwood last 10 to 15 years without treatment and are safe for vegetable gardens.
- Pressure-treated lumber is cheaper and lasts longer but should not touch soil where you grow food.
- Pine and fir rot in 3 to 5 years and are only worth using if you plan to replace the bed frequently.
- Composite boards made from wood fiber and plastic last 20+ years but cost two to three times more than cedar.
- Avoid railroad ties and old utility poles — they contain creosote or other preservatives that contaminate soil.
Pressure-treated lumber costs less but has restrictions
Modern pressure-treated wood (treated after 2004) is safe for raised beds because it no longer contains arsenic. The current treatment uses copper-based compounds that prevent rot. Pressure-treated boards last 15 to 20 years and cost about half as much as cedar — roughly $0.50 to $1.50 per linear foot.
The catch: pressure-treated wood should not directly contact soil where you grow vegetables, herbs, or fruit. The copper can leach into the soil slowly over years. If you use pressure-treated lumber, line the inside with a barrier — landscape fabric, cardboard, or plastic sheeting — between the wood and the soil. This adds labor and cost but makes the bed safe for food.
Pressure-treated wood is fine for ornamental beds or for holding mulch and compost that will not touch edible plants. Many gardeners use it for the frame and cedar for the top edge that they touch while working.
Pine and fir are cheap but rot quickly
Untreated pine and fir boards cost $0.30 to $0.80 per linear foot — the cheapest option. They are soft, straightforward to cut, and widely available at any lumber yard. The downside is severe: they rot in 3 to 5 years when in contact with wet soil.
Pine and fir make sense only if you are building a temporary bed, testing a location before investing in a permanent one, or willing to replace the boards every few years. Some gardeners use them as a short-term solution while saving for cedar. If you go this route, buy the thickest boards available (2 inches rather than 1 inch) to buy yourself a year or two of extra life.
Do not treat untreated pine or fir with preservatives yourself — the chemicals are not designed for food gardens and can be applied unevenly, creating unpredictable leaching.
Composite boards last the longest but cost the most
Composite raised bed boards are made from wood fiber mixed with plastic. Brands like Trex, Fiberon, and Timbertech make them specifically for outdoor use. They do not rot, splinter, or need staining, and they last 20 to 30 years. They are also lighter than wood, which matters if you are moving the bed or building on a deck.
The trade-off is price: composite boards cost $3 to $6 per linear foot, or three to four times more than cedar. A 4-by-8-foot bed in composite runs $200 to $400 in materials alone, while cedar runs $60 to $120. Composite is worth it if you plan to keep the bed for decades and do not want to maintain it, but most home gardeners find cedar a better balance of cost and durability.
Composite boards are safe for food gardens — they do not leach chemicals into soil. Some people dislike their appearance because they look plastic-like, especially when new, though they weather to a more natural gray over time.
Avoid railroad ties, utility poles, and treated wood from before 2004
Railroad ties and old utility poles were treated with creosote or pentachlorophenol, both toxic compounds that leach into soil and persist for years. Even if the wood looks solid, the chemicals remain active. Do not use them for any bed where you grow food, and avoid them for ornamental beds near groundwater or wells.
Pressure-treated wood manufactured before 2004 contained arsenic. If you have an old bed made from pre-2004 treated lumber, do not dig it up and reuse it. The arsenic stays in the wood and will leach into new soil. You can leave it in place if it is not in a food garden, but do not move it.
If you inherit a raised bed and do not know when it was built or what it was treated with, assume it is old. Line it with plastic or cardboard before filling it with soil, or build a new frame on top of the old one.
Thickness and board width affect cost and longevity
Raised bed boards come in standard thicknesses: 1 inch (actual thickness 0.75 inches) and 2 inches (actual thickness 1.5 inches). Thicker boards last longer because they have more wood to rot away before failing. A 2-inch cedar board lasts 2 to 3 years longer than a 1-inch board made from the same wood.
Width matters for how deep your bed will be. Standard widths are 6, 8, 10, and 12 inches. A 12-inch-deep bed holds more soil and drains better than a 6-inch bed, but costs more and is harder to fill. Most gardeners use 8 to 10 inches as a compromise — deep enough for most vegetables and herbs, not so deep that you waste soil or money.
Stacking boards (using two 6-inch boards instead of one 12-inch board) is cheaper per linear foot but creates a weaker frame because the boards can shift against each other. If you stack, use corner brackets or bolts to lock the boards together.
Comparing wood types side by side
| Wood Type | Lifespan | Cost per Linear Foot | Safe for Food | Maintenance |
|---|---|---|---|---|
| Cedar heartwood | 10–15 years | $1–$3 | Yes | None required; optional staining |
| Redwood heartwood | 10–15 years | $2–$4 | Yes | None required; optional staining |
| Pressure-treated (post-2004) | 15–20 years | $0.50–$1.50 | Only with soil barrier | None |
| Pine or fir (untreated) | 3–5 years | $0.30–$0.80 | Yes | None |
| Composite (wood-plastic) | 20–30 years | $3–$6 | Yes | Occasional cleaning |
Frequently Asked Questions
Can I use reclaimed wood from an old barn or fence?
Only if you know what it was treated with. Reclaimed wood from barns built before the 1980s may contain lead paint or unknown preservatives. Reclaimed fence wood is often pressure-treated with old formulas. If you cannot verify the source and treatment, do not use it for a food garden. Reclaimed cedar or redwood from a known source is safe.
Do I need to seal cedar or redwood?
No. Cedar and redwood heartwood resist rot without sealant. Sealing slows weathering and graying but is optional. If you seal, use a water-based stain or sealant rated for food gardens, not oil-based products. Reapply every 2 to 3 years if you want to maintain color.
What if I line pressure-treated wood with plastic — is that enough?
Yes, a plastic or landscape fabric barrier between the wood and soil stops copper leaching. Make sure the barrier covers all interior surfaces and does not tear. Cardboard works too but breaks down after a year or two, so you may need to replace it.
Can I use treated wood for a bed where I grow ornamental plants only?
Yes. Pressure-treated wood is safe for ornamental beds, mulch beds, and anywhere food does not touch the soil. The copper compounds do not harm flowers, shrubs, or decorative plants.
How do I know if old pressure-treated wood contains arsenic?
If the wood was treated before 2004, assume it contains arsenic. Pressure-treated lumber sold in the United States after December 2003 uses copper-based treatment instead. Check the end of the board for a stamp with a date, or ask the seller when it was treated. When in doubt, do not use it for food gardens.