🍈 Cas (*Psidium friedrichsthalianum*)
🔤 Name English / nombre español / Name Deutsch
Cas / Cas / Cas
📄 General description
The Cas tree (Psidium friedrichsthalianum) is a small to medium-sized fruit tree native to Central America and closely related to the common guava. It is well adapted to tropical and subtropical climates, and particularly popular in Costa Rica for its uniquely tart fruit, which is traditionally used to prepare the beloved “jugo de cas.”
The tree grows densely with slightly leathery green leaves and produces small, round fruits that are pale green to yellow when ripe. Cas juice has a citrusy-sour flavor that is both refreshing and distinct, and the fruit is often harvested just as it falls from the tree.
🌿 Botanical Characteristics:
Family
Myrtaceae / (Myrtle family)
Growth and Structure
The Cas tree belongs to the Myrtaceae family, which also includes guava (Psidium guajava), feijoa, and eucalyptus. Members of this family are typically aromatic and have opposite leaves with glandular dots. Cas trees are small to medium-sized and can grow up to 6–10 m tall. They often develop a dense, rounded canopy with multiple branches and a relatively short trunk. Growth is typically vigorous under favorable conditions, especially in humid tropical climates.
Leaves
The leaves are simple, opposite, and oblong to elliptical in shape. They are dark green, leathery, and have a slightly glossy surface with visible veins. When crushed, the leaves release a faintly aromatic scent.
Flowers
Cas trees produce small, white flowers with five petals and numerous stamens, typical of the Myrtaceae family. The flowers are borne singly or in small clusters in the leaf axils and are lightly fragrant.
Pollination
Pollination is primarily by insects (entomophilous), especially bees, which are attracted to the flowers’ nectar and pollen. Cross-pollination may increase fruit set, though the species can also self-pollinate.
Sexual System
Hermaphroditic
Sexual System Notes
Each flower contains both male (stamens) and female (pistil) reproductive organs.
🌤️ Soil and Climate Preferences
Cas thrives in tropical and subtropical climates with abundant rainfall and moderate elevation. It prefers well-drained, slightly acidic to neutral soils rich in organic matter, but can tolerate a range of soil types. The tree grows best in full sun but can also handle partial shade. Although moderately drought-tolerant once established, it produces better fruit with consistent moisture.
Cas is typically found between 600 and 1,800 m elevation in Central America and is well adapted to the humid conditions of Costa Rica’s highlands and Caribbean foothills.
🍈 Fruit and Use:
General Use
The fruit of Psidium friedrichsthalianum, known as cas, is small, round, and typically pale green to yellow when ripe. It has a thin skin, soft and Cas is best known for its use in beverages, especially the iconic “jugo de cas” – a tart and refreshing drink made by blending the pulp with water and sugar, then straining the mixture. The fruit is rarely eaten raw due to its intense acidity but is sometimes used for jams, preserves, vinegar, or fermented drinks. Cas juice is often served chilled and is a beloved staple in Costa Rican homes and sodas. Daily collection from the ground is the preferred harvest method, as ripe fruits fall naturally and are at peak flavor. The soft ground below the tree should be kept clear to prevent damage and ensure clean collection.
Ripening Season in Costa Rica
Cas trees typically begin fruiting during the transition from dry to rainy season, often starting around March or April, with fruit ripening continuing through June or July, depending on local climate. In very humid lowland areas like the Caribbean coast, fruiting may begin earlier or extend slightly longer.
Common Fruit Traits
The fruit is small to medium-sized, round, and light green to pale yellow when ripe. It has thin skin, soft white to yellowish pulp, and numerous small seeds. The flavor is sharply acidic with a distinctive citrusy aroma and astringency. Fully ripe fruits are soft and aromatic and must be used quickly due to their short shelf lif
Climacteric Category
Slightly climacteric
👉🏻 Climacteric category overview
Climacteric Category Notes
Cas fruits exhibit limited post-harvest ripening. While they may soften and become slightly more aromatic after falling, their flavor does not significantly improve. Optimal taste and texture are reached when fruits fall naturally from the tree. Unripe, green fruits do not ripen well off the tree and remain too acidic and firm.
🌱 Propagation and Grafting
Cas is most commonly propagated from seed, as the seeds germinate readily under moist tropical conditions. Seedlings grow vigorously and typically begin fruiting within 3 to 5 years. Seed propagation maintains strong genetic diversity but may result in variation in fruit quality and size.
Vegetative propagation (e.g. cuttings or grafting) is less common, but potentially useful for replicating trees with especially desirable fruit traits. Grafting techniques such as cleft or side veneer grafting may be used, particularly in experimental or commercial settings, although documented success rates for Psidium friedrichsthalianum are limited compared to common guava (Psidium guajava).
At the finca, propagation is currently done from naturally dropped seeds. Seedlings growing near mature trees may be transplanted if needed, with care taken to avoid root damage.
✂️ Care & Challenges:
Pruning
Cas trees benefit from light to moderate pruning to maintain an open canopy and manageable height. Pruning is typically done after the fruiting season, removing dead, crossing, or overly vertical branches. If grown in residential or agroforestry settings, height reduction may be desirable to ease fruit collection. Severe pruning should be avoided, as it may stress the tree or delay fruiting.
Diseases and Pests
Cas is generally a hardy tree, but it can be affected by fruit flies (*Anastrepha* spp.), which may infest fallen or overripe fruits, as well as by anthracnose (a fungal infection) in very humid conditions, especially when airflow is poor. Leaf spot diseases may also occur, though they are usually minor. Occasionally, leaf-chewing insects and caterpillars may be present. Good hygiene practices, such as the removal of fallen fruits, pruning to improve ventilation, and regular ground maintenance, help minimize disease pressure.
Soil and Fertilization
Cas prefers slightly acidic to neutral, well-drained soils rich in organic matter. At planting time, compost or aged manure can be added to improve soil structure and fertility. Periodic applications of compost or bokashi support healthy growth and fruiting. In lean soils, potassium-rich organic materials may help improve fruit quality. Avoid waterlogging, as it may promote root diseases.
🧺 Harvest Notes
Cas fruits are not typically harvested from the tree but rather collected from the ground once they fall naturally, indicating peak ripeness. Fallen fruits are soft, aromatic, and juicier than those picked prematurely. Because of their high perishability, they should be processed within one to two days after collection. To minimize fruit loss and ensure cleanliness, the ground beneath fruiting Cas trees should be kept clear and soft, ideally with regular trimming using a string trimmer (motoguadaña). Daily collection during peak season is recommended, especially in humid environments where ants and fruit flies are active. The fruiting season generally lasts for several weeks, and yields can be substantial depending on the tree’s age and health. Slight bruising from the fall is common but usually does not affect processing into juice or jam.
📍 Individuals in the field
👉 Cas (*Psidium friedrichsthalianum*) – Banana – Field
📷 Photos