Concept Explanation
Evergreen trees keep their leaves all year long. While individual leaves do fall and get replaced, the tree never appears bare—there's always green foliage on the branches.
How It Works
Continuous Replacement:
- Old leaves shed gradually
- New leaves grow continuously
- Tree always has full canopy
- Individual leaves may last 1-4 years
Seasonal Variation:
- May have growth flushes in certain seasons
- Can look denser or lighter at different times
- But never completely bare
Evergreen vs. Deciduous
Evergreen:
- Leaves year-round
- Gradual leaf replacement
- Consistent appearance
- Continuous photosynthesis
- Example: Guayabo, Mango, Avocado
Deciduous:
- Drops all leaves seasonally
- Bare period each year
- Dramatic seasonal changes
- Dormant period
- Example: Guanacaste, Pochote, Oak
Semi-Deciduous (Semi-Evergreen):
- Drops some but not all leaves
- May be bare for brief period
- Variable based on conditions
- Common in seasonal tropics
Why Be Evergreen?
Advantages:
- Continuous photosynthesis
- No energy spent regrowing all leaves
- Better in stable climates
- Year-round shade provision
- Continuous wildlife food source
Trade-offs:
- Must maintain leaves through dry season
- Needs consistent water supply
- Leaves more vulnerable to pests year-round
- Higher maintenance cost in some ways
In Costa Rican Climate
Costa Rica's climate influences leaf retention:
Caribbean Side:
- Higher rainfall year-round
- More evergreen species
- Less seasonal stress
Pacific Dry Forest:
- Strong dry season
- More deciduous trees
- Water conservation strategy
- Some evergreens adapted to drought
Cloud Forests:
- Consistent moisture
- Predominantly evergreen
- Year-round cloud cover
- Cool, stable conditions
Practical Considerations
For Landscaping:
- Year-round shade
- Consistent appearance
- Privacy screening
- Leaf litter throughout year (not seasonal)
- May need more water in dry season
Wildlife Value:
- Consistent shelter
- Year-round nesting sites
- Evergreen food sources for some species
- Winter refuge for migratory birds
Examples in Costa Rica
True Evergreens:
- Guayabo (Psidium guajava): Evergreen fruit tree
- Laurel (Cordia alliodora): Mostly evergreen
- Aguacate (Persea americana): Evergreen with growth flushes
- Mango (Mangifera indica): Evergreen (introduced)
- Most palms: True evergreens
Common Deciduous (for comparison):
- Guanacaste (Enterolobium cyclocarpum)
- Ceiba (Ceiba pentandra)
- Pochote (Pachira quinata)
Identification Tips
Look for:
- Full foliage during dry season (January-April)
- No bare branches period
- Old yellow/brown leaves mixed with green ones
- Consistent canopy density year-round
Note: Semi-Deciduous Challenge
Many tropical trees are "facultatively deciduous":
- May drop leaves in severe drought
- Retain leaves in wetter years
- Behavior varies by microclimate
- Hard to categorize strictly
Evolutionary Context
Tropical Evergreens:
- Common in stable, wet climates
- Leaves adapted to year-round function
- Often have tough, long-lasting leaves
- Efficient nutrient use
Temperate Evergreens:
- Often conifers (pines, firs)
- Needle-shaped leaves reduce water loss
- Adapted to year-round cold
- Different strategy than tropical species