Standing in front of a lumber rack labeled "cedar" without understanding grading is a reliable way to overspend or underbuy. A top-grade clear cedar board costs three to five times what a knotty common board does, and for a raised bed buried in the ground, that premium buys nothing useful. For a visible planter box where appearance matters, that premium is entirely justified. Cedar grading determines what you pay and what you get — and matching grade to application is one of the more practical skills in garden woodworking.
How Cedar Lumber Is Graded
Cedar is graded by appearance, not structural strength. Unlike framing lumber — which is graded for load-bearing capacity — cedar appearance grades are based on the number, size, and location of knots, the presence of sapwood, and the overall quality of the surface. The grading systems differ slightly between Western red cedar and Eastern white cedar, and between lumber associations, but the core categories are consistent.
The main grading organizations are the Western Red Cedar Lumber Association (WRCLA) for Western red cedar and the Northern White Cedar (NWC) standards used in the Northeast. Big-box retailers often use simplified in-house grading labels rather than formal association grades, which can be confusing.
Western Red Cedar Grades
Clear Grades (Clear Heart, A, B)
Clear grades contain no knots, or only very small, tight knots on the less-visible face. "Clear Heart" is the premium designation — heartwood only, no sapwood, no knots. This is the grade used for fine furniture, musical instrument parts, and high-end exterior millwork. For garden projects, Clear Heart cedar is overkill and represents significant unnecessary cost.
"A" and "B" clear grades allow a small number of tight knots on one face and occasional sapwood. They produce an attractive finished surface and are appropriate for visible planter boxes, window boxes, and garden furniture where appearance is part of the design intent.
Architectural Grades (Select, Select Tight Knot)
Select grades are the workhorses of outdoor finish carpentry. "Select Tight Knot" (STK) allows sound, tight knots of up to 1.5 inches but no loose knots or knotholes. The surface is consistent and attractive without the premium cost of clear grades. STK cedar is the most popular choice for deck boards, fence boards, and visible raised bed sides where a clean appearance is desired but perfection is not required.
For most garden planter projects following a container gardening plan, STK cedar represents the best balance of appearance and cost.
Common Grades (1 Common, 2 Common, 3 Common)
Common grades allow larger, more numerous knots and may include loose knots and knotholes. Number 1 Common is still a serviceable board with no knotholes larger than 1 inch. Number 2 and 3 Common are utility grades — structurally sound but visually inconsistent, with large knots and frequent surface defects.
For below-grade and soil-contact applications — the back faces of raised bed walls, internal framing, and structural components that will never be seen — Common grades are entirely adequate. The wood's rot resistance does not change with appearance grade. A knotty Number 2 Common board will last just as long in soil contact as a Clear Heart board, at a fraction of the price.
Eastern White Cedar Grades
Eastern white cedar sold through regional mills in the Northeast is often graded informally as "clear," "knotty," or "utility," sometimes with numeric designations. The formal NWC grading system uses grades similar to Western red cedar's system, but the smaller tree size means truly wide, clear Eastern white cedar boards are rare and carry a significant premium.
Rough-sawn Eastern white cedar from regional mills is often sold without formal grading. When purchasing directly from a mill, inspect boards individually and ask about heartwood percentage — the darker, aromatic heartwood is what provides rot resistance. Light-colored sapwood boards offer significantly less natural durability.
What to Look for on Any Cedar Board
Heartwood vs. Sapwood
The most important variable in cedar's performance is heartwood content. Heartwood is the dark, aromatic core of the tree. Sapwood is the pale outer layer. Natural rot-resistance resides almost entirely in the heartwood. A board that is mostly sapwood will decay like pine, regardless of species.
When selecting cedar for soil-contact applications — the lower courses of a raised bed wall, the bottom boards of a planter box — choose boards with the maximum heartwood content. Hold the board up to the light and look for the distinct color line between heartwood and sapwood. Avoid boards where sapwood accounts for more than 20% of the cross-section on soil-contact faces.
Grain Orientation
Vertical grain (quartersawn) cedar is more dimensionally stable than flat grain. Vertical grain boards show parallel lines running the length of the board; flat grain shows arching or cathedral patterns. For garden applications where dimensional stability matters — planter boxes, window boxes, any structure with visible joinery — vertical grain is preferable. For utilitarian raised beds, grain orientation is a secondary concern.
Moisture Content
Cedar sold at home improvement retailers is typically kiln-dried to 19% moisture content or less. Rough-sawn lumber from regional mills may be green (high moisture content). Green cedar will shrink and check as it dries in service. Build with slightly wider gaps in joinery if using green lumber, and expect boards to narrow by 1/4 to 1/2 inch in width as they dry. This is not a structural problem but can open gap joints if not anticipated.
Grade Selection by Application
For rough-cut raised bed construction where the boards will be in soil contact and partially hidden by plants and mulch, Number 2 Common or Utility grades offer the best value. The rot resistance is unchanged, and the cosmetic defects are invisible in use.
For visible planters, window boxes, and garden furniture that will be prominent in the landscape, Select Tight Knot or better provides an attractive surface without the cost of clear grades. For showpiece planters or fine garden structures where appearance is the primary design element, A or B clear grades deliver a genuinely furniture-quality surface.
Frequently Asked Questions
Does a higher grade of cedar last longer outdoors?
Not necessarily. Grade reflects appearance — knot frequency and size — not rot resistance. The key variable for durability is heartwood content, which is not formally graded in most systems. A knotty Common board with high heartwood content will outlast a Clear board with significant sapwood in soil-contact applications.
What does "STK" mean on cedar lumber?
STK stands for "Select Tight Knot." It is one of the most common cedar appearance grades and allows sound, tight knots up to approximately 1.5 inches while prohibiting loose knots and knotholes. It is the standard choice for deck boards, fence boards, and visible garden structures.
Can knotty cedar be used for food-growing raised beds?
Yes. Knots are simply dense wood fibers and contain no harmful compounds. Knotty cedar is structurally sound and chemically identical to clear cedar for food-growing purposes. The choice between grades in raised bed construction is aesthetic and economic, not food-safety related.
Is rough-sawn cedar better than surfaced cedar for garden use?
Rough-sawn cedar has a slightly larger actual dimension, which adds structural mass. The rougher surface also grips paint and stain better. For garden beds where appearance is secondary, rough-sawn is often less expensive and perfectly functional. For fine planters and visible garden structures, surfaced (S4S) cedar produces cleaner joints and a more refined appearance.
Why do big-box retailers label cedar with different grades than specialty mills?
Large retailers often use simplified or proprietary grading labels to standardize purchasing across regions. A board labeled "Premium" at a home center may correspond to Select or STK in formal grading, while "Standard" may correspond to Number 2 Common. When grade precision matters, a specialty lumber yard or regional mill will use formal WRCLA or NWC grades that are more directly comparable.