Visual Description
A compound leaf consists of multiple leaflets attached to a single leaf stem (petiole). Each leaflet looks like a small leaf, but all leaflets together form one functional leaf.
How to Identify
Key Test: Look for the axillary bud. A true leaf has a bud where it attaches to the branch. Leaflets do NOT have buds at their attachment points.
Types of Compound Leaves
Pinnately Compound
- Leaflets arranged along both sides of a central axis (rachis)
- Looks like a feather
- Example: Walnut, Ash, Guanacaste
Palmately Compound
- Leaflets radiate from a single point
- Looks like fingers on a hand
- Example: Horse Chestnut, Ceiba, Buckeye
Bipinnate (Twice-Compound)
- Each leaflet is itself divided into smaller leaflets
- Very complex appearance
- Common in Mimosaceae family
Why It Matters
Compound leaves offer several advantages:
- Reduced wind resistance: Leaflets can move independently
- Efficient water shedding: Rain drips off easily
- Flexible light capture: Individual leaflets can adjust position
- Reduced herbivore damage: Loss of one leaflet doesn't destroy entire leaf
Common Confusion
Is it a compound leaf or a branch with simple leaves?
Look for:
- Buds: Only present at base of true leaves, not leaflets
- Arrangement: Leaflets typically more uniform in size
- Attachment: All leaflets fall together as one unit
Examples in Costa Rica
Pinnately Compound:
- Guanacaste (Enterolobium cyclocarpum)
- Mahogany (Swietenia macrophylla)
- Poró (Erythrina poeppigiana)
Palmately Compound:
- Ceiba (Ceiba pentandra)
- Pochote (Pachira quinata)