Why Is Cedar Wood Red? The Natural Oils Behind the Color
Cedar’s reddish-brown color comes from tannins and extractives — including thujaplicins and plicatic acid — concentrated in the heartwood, not the pale sapwood around it. These same compounds make cedar naturally resistant to rot and insects, which is why builders trust it outdoors without chemical treatment. This guide covers the real chemistry behind the color, how the shade differs between Western Red Cedar, Eastern Red Cedar, and aromatic cedar, and why that red eventually turns silver-gray outside.
What Makes Cedar’s Heartwood Red?
Cedar’s red color sits almost entirely in the heartwood — the dense, structural core of the trunk — not the pale sapwood that surrounds it. As a cedar tree ages, the innermost sapwood cells convert to heartwood and fill with extractives: plicatic acid, thujaplicins (a group of tropolone compounds), and related polyphenols that woodworkers commonly lump together as “tannins.” These compounds are deposited for a defensive reason, not a cosmetic one — they make the wood toxic to decay fungi and unappealing to insects, and the reddish-brown pigment is a side effect of that chemistry rather than its purpose.
The two families of extractives don’t play identical roles. Thujaplicins act as natural fungicides that inhibit fungal growth at the wood’s surface. Plicatic acid — the extractive present in the highest concentration in Western Red Cedar heartwood — is the compound most closely tied to how long a board resists decay in ground contact. Sapwood contains almost none of either, which is why sapwood boards stay pale, rot quickly outdoors, and are usually graded out of exterior lumber.
Does Cedar’s Red Color Vary by Species?
Not all wood sold as “cedar” is the same tree, and the depth of red varies by species along with hardness and durability. None of the cedars sold in North America are true cedars (genus Cedrus, in the pine family) — they’re members of the cypress and juniper families that earned the common name for their color and scent. See our full red cedar vs. white cedar comparison for a wider species breakdown.
| Species | Botanical Name | Heartwood Color | Key Color Compound | Janka Hardness |
|---|---|---|---|---|
| Western Red Cedar | Thuja plicata | Light tan to reddish-brown | Plicatic acid + thujaplicins | ~350 lbf |
| Eastern Red Cedar / Aromatic Cedar | Juniperus virginiana | Reddish to violet-brown, often streaked | Related extractives, higher concentration | ~900 lbf |
| Spanish Cedar | Cedrela odorata | Pinkish to reddish-brown | Different extractive profile (true hardwood) | ~600 lbf |
| True Cedar (for contrast) | Cedrus spp. | Pale golden-brown, rarely reddish | Low extractive content | Varies by species |
Eastern Red Cedar and aromatic cedar are the same tree (Juniperus virginiana) — “aromatic cedar” just refers to boards cut to show off the scent and color contrast used in closet linings and chests. Its heartwood runs darker and more purple-brown than Western Red Cedar, and at roughly 900 lbf on the Janka scale it’s more than twice as hard. Western Red Cedar (Thuja plicata) is the lighter, pinker board most commonly sold for decking and siding, and its lower density is part of why it’s easier to mill and less prone to splitting when nailed near an edge.
Why Does Red Cedar Turn Gray Outdoors?
Left unfinished outside, cedar’s red fades to silver-gray — but the change is only skin-deep. UV radiation breaks down lignin in the outermost wood cells, and that photodegradation doesn’t reach further than about 75 microns below the surface, roughly the thickness of a sheet of paper. Rain then washes the broken-down lignin and surface extractives away, leaving the gray cellulose skeleton behind while the red-brown wood underneath stays fully intact.
📊 UV photodegradation of wood surfaces penetrates no deeper than approximately 75 microns (about 0.003 in). — Source: USDA Forest Service, Forest Products Laboratory wood-weathering research.
That’s also why sanding or planing a weathered cedar board restores the red color almost instantly — the degraded layer is only a fraction of a millimeter deep. For the full timeline of how fast graying happens in different climates and whether it’s reversible without resurfacing, see our dedicated breakdown of does cedar turn gray.
How to Keep Cedar’s Red Color From Fading
A UV-blocking exterior finish is the only thing that meaningfully slows this process. Clear film finishes and film-forming spar varnishes tend to fail fastest outdoors because UV degrades the film itself, while penetrating oil finishes with UV inhibitors need reapplication every 1–2 years to stay effective. Regular cleaning with mild soap and water also helps — built-up dirt and mildew dull the color independently of UV damage, and harsh chemical cleaners can strip surface extractives prematurely.
Indoors, cedar keeps its red color far longer since window glass already blocks most UV-B, but direct sun through an unshaded window will still visibly bleach a panel over a few years.
“Any cedar board looks brightest the day it comes off the blade — even a few weeks sitting exposed on a lumber rack under shop lights takes some of the shine off it. If color match matters for a project, I mill and finish the visible faces last.”
— Md Meraj, Woodworking Advisor
Frequently Asked Questions
Why Does Cedar Wood Turn Red?
Cedar turns red because of tannins and extractives — mainly plicatic acid and thujaplicins — that build up in the heartwood as the tree matures. This isn’t caused by sunlight; sunlight is actually what fades red cedar to gray over time, the opposite effect.
Is Cedar Naturally Red?
Yes. Freshly milled cedar heartwood is naturally reddish-brown without any stain or dye. The sapwood around it stays pale because it hasn’t developed the same concentration of extractives.
What Is So Special About Red Cedar Wood?
Red cedar resists rot and insects without chemical treatment because the same extractives that color it are mildly toxic to fungi and unappealing to insects. That natural durability is a major reason it’s a standard choice for decking, siding, and fencing.
Is Red Cedar a Real Cedar?
No. Western Red Cedar (Thuja plicata) and Eastern Red Cedar (Juniperus virginiana) both belong to the cypress family, not the true cedar genus Cedrus, which is in the pine family. They earned the name for scent and color, not botanical relation.
Why Does Red Cedar Turn Gray Outdoors?
UV light breaks down lignin in the top layer of wood cells — no deeper than about 75 microns — and rain washes the byproducts away, leaving a silver-gray surface. The reddish-brown wood beneath is unaffected and reappears if the surface is sanded or planed off.
Conclusion
Cedar’s red color is a heartwood chemistry story, not a finish or a stain — plicatic acid and thujaplicins that protect the wood also happen to color it. That color runs deepest in fresh-cut Eastern Red Cedar and stays reddest longest indoors or under a UV-blocking finish; left bare outside, expect it to silver within a few seasons as the surface — and only the surface — weathers away.
