Myrtaceae

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Myrtle Family

Psidium guajava L., a tree in the Myrtaceae. Note the opposite leaves with veins looping into each other at the margin. The fruits on this specimen are immature; they can reach the size of a softball when ripe. Un árbol. Note las hojas opuestas con venas que se entrelazan cerca de la márgen. Los frutos de esta muestra están inmaduras; al madurar alcanzan mayor tamaño.

Description: The Myrtaceae are primarily shrubs and understory trees in this area, and they are easy to recognize vegetatively. All of the New World species have simple, opposite leaves with punctations (tiny translucent dots of sequestered oil in the leaf, which are visible through a hand lens when the leaf is held up to the light). The crushed leaf has a pleasant, fruity or spicy aroma. The bark is usually whitish or reddish, thin and papery, and often flaking.

Economic uses: Many New World species of Myrtaceae have edible fruit; the best-known is Psidium guajava, the guava or guayaba. In Costa Rica you’ll also find the more acidic cas (P. friedrichsthalianum). The Old World genera Eucalyptus and Melaleuca are widely cultivated as ornamentals and shade trees.

Descripción: Casi todas las Myrtaceas de esta área son arbustos y árboles pequeños, y es fácil identificarlas estérilmente. Todas las especies de esta zona tienen hojas simples y opuestas con puntos translúcidos (motas de aceite dentro de la hoja, que se pueden ver a contra la luz con una lupa de mano). La hoja estrujada tiene un olor dulce similar a frutas o especias. La corteza es rojiza o blancuzca, fina, y usualmente escamosa.

Usos económicos: Muchas Myrtaceas del nuevo mundo tienen frutos comestibles. En Costa Rica las plantas más comunes son la guayaba (Psidium guajava) y el cas (P. friedrichsthalianum). Los géneros Eucalyptus y Melaleuca, del viejo mundo, son cultivados en muchas partes como ornamentales y para sombra.

Genera/species at La Selva: 5/16: Eugenia (10), Myrcia (2), Myrciaria (1), Psidium (2), Syzygium (1).

FIELD MARKS – opposite, simple leaves, characteristic odor of guava or eucalyptus, secondary veins join near margin (simulating a peripheral vein), pellucid dots.

Myrtaceae showing flowers with conspicuous white stamens.	Psidium guajava (Guava) with opposite leaves, secondary veins that loop and join near the leaf margin, and pellucid dots.
Close-up of Guava leaf showing pellucid dots (glandular punctations).	Guava fruit.
Psidium friedrichsthalianum is used to make the acidic fruit drink known as “cas”.	Flowers of Psidium friedrichsthalianum bearing conspicuous white stamens.
Exfoliating bark of Psidium friedrichsthalianum.

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