Cas
Psidium friedrichsthalianum
Native Region
Costa Rica and Panama
Max Height
5-8 meters (16-26 feet)
Family
Myrtaceae
Conservation
LC
Uses
Season
Flowering
Mar-May
Fruiting
Jun-Sep
Cas (Costa Rican Guava)
The Cas (Psidium friedrichsthalianum), known as Costa Rican Guava or Sour Guava, is perhaps the most distinctly Costa Rican fruit tree. While the common guava is eaten fresh throughout the tropics, the cas has carved its own niche—its intensely tart, aromatic fruits are transformed into refresco de cas, one of the most iconic and refreshing beverages in Costa Rican cuisine. Found primarily in Costa Rica and Panama's highlands, this small tree represents a unique piece of Central American biodiversity and culinary heritage. No visit to a Costa Rican soda (local restaurant) is complete without trying this uniquely tangy, fragrant drink.
Quick Reference
- Scientific Name
- Psidium friedrichsthalianum
- Family
- Myrtaceae
- Maximum Height
- 5-8 m
- Native Region
- Costa Rica & Panama
- Conservation
- Least Concern
- Key Trait
- Intensely tart green fruit
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Taxonomy and Classification
- Psidium: Greek for "pomegranate" (descriptive of fruit structure) - friedrichsthalianum: Honors German botanist Emanuel Ritter von Friedrichsthal - Cas: Local Costa Rican name of uncertain origin - Closely related to common guava (Psidium guajava)
Common Names
| Language/Region | Common Name(s) | Notes |
|---|---|---|
| Spanish (CR) | Cas, Guayaba Ácida | Most common local names |
| English | Costa Rican Guava, Sour Guava | Descriptive names |
| Panama | Cas | Same as Costa Rica |
| Scientific lit. | Acidulous Guava | Reference to tartness |
Distinguishing from Common Guava
| Feature | Cas (P. friedrichsthalianum) | Guayabo (P. guajava) |
|---|---|---|
| Fruit taste | Very sour/tart | Sweet to mildly tart |
| Fruit size | Smaller (3-5 cm) | Larger (5-12 cm) |
| Fruit color | Green when ripe | Yellow/green when ripe |
| Flesh color | White to cream | White, pink, or red |
| Eating fresh | Rarely done (too sour) | Commonly eaten fresh |
| Primary use | Juice/beverages | Fresh or processed |
| Elevation | 500-2000m | 0-1500m |
| Distribution | CR & Panama mainly | Tropical Americas wide |
Physical Description
General Form
The Cas is a small to medium evergreen tree with a dense, rounded canopy. It resembles its cousin the common guava but tends to be smaller and more compact. The tree is often multi-stemmed and well-suited to home gardens and small orchards.
Identification Features
Bark and Trunk
- Bark color: Smooth, reddish-brown
- Texture: Peeling in thin layers
- Pattern: Mottled appearance
- Trunk: Often multi-stemmed
Leaves
- Type: Simple, opposite
- Shape: Elliptic to oblong
- Size: 5-12 cm long
- Texture: Leathery
- Color: Dark green, lighter beneath
- Venation: Prominent parallel veins
- Scent: Aromatic when crushed (guava-like)
Flowers
- Size: 2-3 cm diameter
- Color: White
- Petals: 4-5, with numerous stamens
- Fragrance: Sweet, typical guava scent
- Location: Leaf axils
- Timing: Dry season into early rainy season
Fruit
- Shape: Round to slightly oval
- Size: 3-5 cm diameter
- Skin: Green, thin, smooth
- Flesh: White to cream, granular
- Seeds: Numerous, small, hard
- Taste: VERY TART (much more than common guava)
- Aroma: Intense, fragrant, characteristic
Unlike many fruits, ripe cas: - Stays green (doesn't turn yellow) - Softens slightly when gently pressed - Develops intense aroma that's unmistakable - Falls from tree naturally when fully ripe The intense sourness is normal—it's prized for juice, not fresh eating!
Ecology and Habitat
Natural Distribution
| Region | Status | Elevation |
|---|---|---|
| Costa Rica - Central Valley | Native, common | 800-1500m |
| Costa Rica - highlands | Native | 1000-2000m |
| Panama | Native | Similar elevations |
| Other Central America | Rare/absent | Limited distribution |
Climate Preferences
Optimal Conditions
- Temperature: 18-25°C (64-77°F)
- Rainfall: 1500-2500 mm annually
- Elevation: 500-2000 m (highland species)
- Climate: Cool tropical to subtropical
- Soil: Well-drained, fertile
Tolerances
- Cold: Moderate tolerance (better than common guava)
- Heat: Less tolerant of extreme heat
- Drought: Moderate tolerance
- Wind: Good tolerance
- Poor soils: Adaptable
Ecological Role
Pollinators
- Bees: Primary pollinators
- Self-pollination: Possible but less productive
- Cross-pollination: Improves fruit set
Wildlife Value
- Birds: Eat ripe fallen fruit
- Small mammals: Consume fruit
- Native bees: Important nectar source
Highland Ecosystem
- Native species: Part of natural highland flora
- Garden cultivation: Most trees are cultivated
- Gene pool: Important genetic resource
- Endemic character: Unique to limited region
Uses
Culinary Applications
| Preparation | Description | Popularity |
|---|---|---|
| Refresco de Cas | Blended juice with sugar and water | ICONIC - most common use |
| Batido de Cas | Blended with milk/ice cream | Very popular |
| Ice cream | Cas-flavored helado | Beloved flavor |
| Preserves | Jam and jelly | Traditional preparation |
| Sorbet | Frozen dessert | Refreshing treat |
| Fresh (rare) | Eaten with salt/sugar | Not common due to sourness |
Classic Refresco de Cas Recipe
Costa Rica's Signature Drink
Ingredients:
- 4-5 ripe cas fruits
- 1 liter cold water
- Sugar to taste (½ to 1 cup)
- Ice
Preparation:
- Wash fruits and cut in half
- Scoop flesh and seeds into blender
- Add water and blend thoroughly
- Strain through fine mesh to remove seeds
- Add sugar gradually, tasting until balanced
- Serve over ice
Tips:
- The tartness should remain but be balanced by sweetness
- Traditional preparation uses generous sugar
- Can add a splash of lime for extra brightness
- Best served very cold
This drink is found at virtually every soda and restaurant in Costa Rica!
Nutritional Value
| Nutrient | Amount per 100g | % Daily Value |
|---|---|---|
| Calories | 52 kcal | 2% |
| Vitamin C | 180-280 mg | 300-400% |
| Fiber | 5.4 g | 22% |
| Potassium | 280 mg | 6% |
| Vitamin A | 31 IU | 1% |
Cas is exceptionally high in vitamin C—among the highest of any fruit. A single serving of cas juice can provide 3-4 times the daily recommended vitamin C intake!
Traditional Medicine
| Use | Preparation | Notes |
|---|---|---|
| Vitamin C source | Fresh juice | Cold and flu prevention |
| Digestive aid | Juice | Traditional use |
| Fever reduction | Tea from leaves | Folk remedy |
| Diarrhea | Leaf tea | Astringent properties |
Cultivation
Growing Cas
Production in Costa Rica
| Factor | Status | Notes |
|---|---|---|
| Commercial cultivation | Limited | Mostly backyard production |
| Main regions | Central Valley | Ideal climate |
| Harvest season | June-September | Rainy season peak |
| Processing | Fresh juice industry | Restaurants, factories |
| Export | Minimal | Perishable, local demand |
Cultural Significance
In Costa Rican Identity
A Uniquely Costa Rican Fruit
The cas holds a special place in Costa Rican culture:
- National beverage: Refresco de cas is quintessentially Tico
- Home gardens: Found in patios throughout the Central Valley
- Soda culture: No traditional restaurant is complete without it
- Childhood memories: Many Costa Ricans associate it with home
- Local pride: A fruit that's "ours" - not found widely elsewhere
The intense tartness that foreigners find surprising is exactly what Costa Ricans love about it!
Market Presence
- Fresh markets: Sold during season at ferias
- Sodas: Standard beverage option
- Ice cream shops: Popular flavor
- Supermarkets: Fresh and frozen pulp available
- Processing plants: Juice and pulp production
Conservation Status
Status: Least Concern (LC)
The cas is not threatened, but its limited natural range makes genetic conservation important. Most trees are cultivated rather than wild. Maintaining diversity in cultivated populations helps preserve this unique species.
Quick Identification Guide
How to Recognize Cas
- Small tree (5-8 m) similar to common guava 2. Smooth, peeling bark in reddish-brown patches 3. Opposite, aromatic leaves with parallel veins
- Small green fruits (3-5 cm) that stay green when ripe 5. Intensely fragrant with characteristic sour-guava aroma 6. VERY TART taste - this is normal! 7. Highland distribution (500-2000m elevation)
References and Further Reading
| Resource | Type | Focus |
|---|---|---|
| Flora of Costa Rica | Database | Native species documentation |
| CATIE Fruit Trees | Technical | Cultivation information |
| Costa Rican Biodiversity | Database | Distribution data |
| Traditional Costa Rican Cuisine | Cultural | Culinary traditions |
