Heartwood and sapwood are not two different woods. They are two different roles inside the same tree.
This guide explains what sapwood does, what heartwood is, and why the colour contrast exists in many species.
You will learn what the heartwood-sapwood divide actually changes in practice: durability outdoors, finishing behaviour, and timber selection.
By the end, you will know when sapwood is a feature, when it is a risk, and when it simply does not matter.
What Sapwood Is
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Image placeholder: Tree cross-section (zones)
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- Simple log cross-section labelling bark, cambium, sapwood band, heartwood core, and pith.
Sapwood is the living outer wood of the tree.
Its main job is to move water and nutrients up from the roots.
Common traits of sapwood:
- usually lighter in colour
- higher moisture content when freshly cut
- more biologically “active” when the tree is alive
Because sapwood is used to transport fluids, it tends to be more open to things that move through wood.
What Heartwood Is
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Image placeholder: Sapwood vs heartwood board example
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- Photo of a board with visible light sapwood edge and darker heartwood, with a short caption.
Heartwood is older wood in the centre of the tree.
Over time, the tree stops using this zone for transport.
Instead, the cells become blocked and the tree often deposits chemicals into the wood. These deposits are called extractives.
Common traits of heartwood:
- usually darker in colour (though not always)
- often has higher natural durability
- may have different smell, taste, or working behaviour depending on species
Heartwood is not “dead” in a structural sense. It is still the bulk of the tree’s strength. It is just no longer part of the tree’s plumbing.
Why the Colour Difference Happens
Many species develop a strong contrast because heartwood accumulates extractives.
These can change:
- colour
- decay resistance
- how the wood reacts to finishes
Some species show a dramatic difference (for example, many cedars and yews).
Other species show very little difference, so the heartwood and sapwood can be hard to tell apart.
Durability: The Big Practical Difference
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Image placeholder: Outdoor durability comparison
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- Simple 2-panel visual: heartwood-only vs sapwood-included, with notes: “sapwood usually needs treatment outdoors”.
In many species, heartwood is more rot resistant than sapwood.
That is because the extractives can inhibit fungi and insects.
Important practical point:
- Sapwood is usually not durable outdoors unless treated, even if the species is considered durable.
This is why outdoor timber specs often talk about “heartwood only” for certain applications.
Strength and Movement: What Usually Does Not Change Much
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Image placeholder: Same board, two zones
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- Diagram of one board showing sapwood and heartwood in the same piece, captioned: “same grain, same movement directions”.
Heartwood and sapwood are made from the same basic cell structure, so:
- strength differences are often small compared to differences between species
- shrinkage and swelling behaviour is usually similar within the same board
In practice, moisture content, grain orientation, and drying quality have a bigger impact on movement than whether a piece is heartwood or sapwood.
What It Means for Woodworking
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Image placeholder: Finishing/blotching example
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- Photo showing stain/finish taking differently on sapwood vs heartwood (or a simple diagram if no photo).
Appearance decisions
Sapwood can be:
- a feature, if you like contrast
- a defect, if you want a uniform colour
Outdoor decisions
If you are building for exterior use, check:
- whether the species heartwood is durable
- whether sapwood needs treatment or exclusion
Finishing decisions
Heartwood and sapwood can absorb stain and finish differently, which can create blotching or visible banding if you are not expecting it.
What’s Next
Now that heartwood vs sapwood is clear, the next step is earlywood vs latewood — the two bands inside each growth ring and how they affect density, strength, and surface texture.
🔗 Knowledge Network
Species Pages
- Cedar (strong heartwood/sapwood contrast)
- Yew (strong heartwood/sapwood contrast)
- Oak
- Walnut (dramatic heartwood colour, pale sapwood)
- Cherry (heartwood darkens significantly with age/light)
- Elm (distinct heartwood, moderate contrast)
- Douglas Fir (visible heartwood/sapwood boundary in softwood)
- Larch (durable heartwood for a softwood)
Glossary Terms
- Heartwood
- Sapwood
- Extractives
- Durability
- Pith
- Cambium
- Tyloses
- Treatability
- Blotching
- Moisture content
Calculators
- None for this guide
Categories
- Durability
- Wood anatomy
- Extractives
- Treatability
- Colour change
- Finishing behaviour