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From Tree to Table · Part 1 of 9

Tree Anatomy for Woodworkers

Before you pick a board, it helps to know what you are actually looking at. Tree anatomy is not biology trivia — it tells you how finish will read on the face, how sharp your plane needs to be, and why two boards of the same species can behave completely differently on the bench.

When I walk a class through the lumber at Fells Hardwood Supply, we start here. Not with a species list, but with the structure inside the tree. Once you can read earlywood and latewood, heartwood and sapwood, pores and rays, the tags on the bundles start to make sense — and so do the surprises in your shop.

Earlywood vs. latewood

Every growth ring is two seasons stitched together. Earlywood is the lighter, faster spring growth — larger cells, lower density, often softer under a fingernail. Latewood is the darker summer band — tighter cells, higher density, the part that holds up to wear.

In the store, that contrast shows up as stripes on oak, ash, and pine. On maple it can be subtle until you plane a face and watch the latewood bands catch light differently. Species with dramatic early/late contrast (think ring-porous oak) often need more finish work to get a flat sheen. Diffuse-porous woods like hard maple can look glass-smooth with less filling.

When you are choosing stock for a tabletop, run your hand along the face. Heavy latewood bands in a plain-sawn board can telegraph through a film finish as subtle ridges. That is not a defect — it is anatomy. Decide whether you want that character or whether you would rather pay for quarter-sawn stability and a calmer face.

Heartwood vs. sapwood

Heartwood is the older, inactive core. Extractives darken it and often make it more stable and rot-resistant. Sapwood is the living outer ring — lighter, sugar-rich, and more attractive to insects and stain fungi.

At the store, color sorts start with this split. Walnut FAS can legally carry more sapwood in a clear cutting than cherry or maple FAS — NHLA wrote a species exception because walnut yield would collapse otherwise. Steamed walnut blends sap color into heartwood for a uniform brown face; unsteamed walnut keeps the stark sap/heart contrast some makers prefer.

When a customer asks for “all heart, no sap,” that is a color sort on top of grade, not a grade bump. Point them to Prime or Oak Rules walnut if we have it in stock, or help them pick boards face-by-face from an open pack.

Ring-porous vs. diffuse-porous

Vascular anatomy drives how finish behaves and how you identify species at the end grain.

  • Ring-porous (oak, ash, elm): large pores stacked in the earlywood band. Open pores drink stain unevenly unless you fill or seal. In the store, look at a fresh-sawn or skip-planed face — you can often see the pore rows without magnification.
  • Diffuse-porous (maple, birch, poplar, cherry): pores are tiny and evenly distributed. Faces take oil and film finishes smoothly; pore filling is usually optional, not mandatory.
  • Semi-ring-porous (walnut, mahogany): pores are visible but not as dramatic as oak. Finish strategy sits between the two extremes.

Medullary rays

Rays are horizontal cells that move nutrients across the rings. On a quartersawn face they show as shimmering flecks — the “ray fleck” you see in white oak, sycamore, and lacewood. Plain-sawn boards hide most of the ray structure; quarter and rift cuts expose it.

If a customer wants ray fleck for a project, steer them to quartersawn white oak or QS sapele in the store, not the plain-sawn red oak pile. If they need a calm, uniform face, ray fleck is the wrong aesthetic — say that out loud before they buy eight boards.

Grain direction and figuring

Straight grain machines predictably — ideal for first-time joinery students and production work. Interlocked or reversing grain (common in sapele, some mahoganies, and figured maple) fights the plane unless you take lighter cuts, skew the iron, or move to helical tooling.

Figure — curly, birdseye, quilt, spalting, crotch, burl — is beautiful and often less structurally forgiving. Curly maple looks like tiger stripes because fibers ripple through the thickness; planing against that ripple tears out in a heartbeat. Figured stock belongs in the “sharp tools, light passes, maybe scraper finish” conversation, not the “I need twenty identical rails” conversation.

In the store: Pick up two maple boards — one straight-grained, one curly. Compare how light moves across the face and how the end grain looks. That thirty-second exercise saves a return trip when the tear-out shows up at 9 pm on a Sunday.

Oils, resins, and glue-ups

Oily exotics — teak, rosewood, cocobolo, some padauk — can repel water-based glue and finish if surface oils are not dealt with. Wipe with acetone or alcohol on a test offcut before you assume PVA will grab. Some makers default to epoxy on oily species for critical joints.

Ask at the counter if you are unsure. We would rather slow you down for two minutes at purchase than watch a glue-up fail after the boards are milled.