What is Cambium?
The cambium is a paper-thin ring of living cells just beneath a tree's bark. It is the engine of trunk and branch growth — every year it adds a new layer of wood on the inside and a new layer of bark on the outside.
How It Works
Two Types
- Vascular cambium: Produces xylem (wood) inward and phloem (inner bark) outward — responsible for trunk thickening.
- Cork cambium (phellogen): Produces the outer protective bark.
Seasonal Growth
In Costa Rica's tropical climate, cambial activity is often continuous but varies with wet/dry seasons:
- Wet season: Rapid cell division produces broad, light-coloured wood.
- Dry season: Slower growth produces denser, darker wood.
- These alternations create visible growth rings even in the tropics.
Why It Matters
- Tree health: A damaged cambium can kill a branch or the entire tree.
- Grafting: Successful grafts require cambium layers of scion and rootstock to align.
- Timber quality: Cambial growth rate affects wood density and grain.
- Dating: Growth rings produced by the cambium can reveal a tree's age.
Costa Rican Examples
Cedro Amargo (Cedrela odorata)
Rapid cambial growth during the wet season produces the distinctive light-and-dark banding prized in furniture wood.
Cristóbal (Platymiscium pinnatum)
Slow, consistent cambial activity produces the extremely dense, durable heartwood valued in fine woodworking.
Cambium Damage
Common causes of cambial injury in Costa Rica include:
- Machete wounds during trail maintenance
- Fire scars from dry-season burns
- Bark beetles that tunnel through the cambial zone
- Sun scald on suddenly exposed trunks after logging nearby trees