How bark forms, and why it looks the way it does
Bark is the dead outer layer of a tree, sitting over a thin living layer called the phloem. As the trunk thickens each year, the outer layer either stretches, splits or is shed, and which of those happens is what gives a species its signature pattern.
Trees that stretch rather than split keep smooth bark for a long time — beech and many eucalypts. Trees that split form vertical fissures or plates — oaks, elms and most pines. Trees that shed do it in flakes, strips or sheets — plane trees, paperbarks and birches.
The bark features that actually identify a species
- Pattern — smooth, fissured, plated, scaly, peeling, or covered in fine cracks. This is the single most useful feature.
- Fissure depth and direction — shallow vertical, deep vertical, blocky, or a diamond lattice.
- Colour of both the outer and inner layer. Many eucalypts are grey outside and cream, orange or pink where the bark has shed.
- Shedding style — in curls, ribbons, sheets, flakes or patches.
- Lenticels — the small horizontal breathing pores that show clearly on cherry, birch and alder.
- Prickles, thorns or corky ridges on the trunk itself.
Bark patterns at a glance
| Pattern | What you see | Typical trees |
|---|---|---|
| Smooth | Even, unbroken surface, often pale grey | Beech, many eucalypts, holly |
| Fissured | Vertical grooves running up the trunk | Oak, ash, elm, most pines |
| Plated | Deep cracks forming raised blocks | Black poplar, old oaks, persimmon |
| Peeling strips | Long vertical ribbons hanging loose | Paperbark, river birch |
| Flaking patches | Irregular plates dropping to reveal new colour | Plane tree, sycamore, crepe myrtle |
| Powdery or smooth with rings | Faint horizontal banding | Cherry, birch, alder |
| Corky ridges | Winged or ridged projections along the trunk | Sweetgum, winged elm |
Photographing bark so it identifies properly
- Stand back far enough to show the trunk from ground level to about chest height. Pattern only reads at scale.
- Take a second, closer shot of a 20cm square of bark so the texture and fissure depth are clear.
- Get the light across the trunk rather than behind it. Raking light makes fissures visible; flat light hides them.
- Include something for scale — your hand, a coin or a boot.
- If the trunk has shed, photograph the boundary between the old and new bark. That contrast is often the giveaway.
Where bark alone is not enough
Bark narrows a tree down to a family or a shortlist, but it rarely finishes the job on its own. Eucalyptus is the clearest example: dozens of species share a smooth grey trunk and are separated by their buds, fruit and juvenile leaves, not their bark.
If the bark identification comes back with more than one candidate, take one more photo of a leaf, a bud or a seed pod from the same tree. Two features together resolve most trees that bark alone cannot.
Bark that changes with age
- Persimmon starts smooth and grey, then develops deep blocky plates as it matures.
- Cherry stays smooth with prominent horizontal lenticels, but old trees roughen at the base.
- Eucalypts often keep rough bark on the lower trunk and shed it higher up, so the same tree shows two patterns.
- Plane trees flake in patches that leave a camouflage pattern — young trees have almost none.
Bark is the one part of a tree you can identify in every season. Leaves fall, blossom lasts a fortnight and fruit lasts weeks, but the trunk is there in January and in July. That makes bark the most useful fallback when a tree gives you nothing else to work with.
The catch is that bark changes as a tree ages. A young eucalyptus and an old one can look like different species. This guide covers the bark features that hold true, the ones that shift with age, and how to photograph a trunk so an identification is worth trusting.
Frequently Asked Questions
Sometimes, but rarely with certainty. Bark reliably narrows a tree to a family or a shortlist. Species-level identification usually needs a second feature such as a leaf, bud or seed pod.