Costa Rican guava/Cas (Psidium friedrichsthalianum) – seeds – The aromatic cas guava for exotic refreshments

Psidium friedrichsthalianum, known in Central America mainly as “cas,” is a very special type of guava whose flavor is distinctly different from that of the classic, sweet apple guava. This evergreen shrub stands out for its attractive foliage, delicate white flowers, and remarkably smooth bark. Its real highlight, however, is its round, bright yellow fruit when ripe. The fruit gives off an intense, fruity aroma, but is extremely sour when eaten raw. It is precisely this refreshing tartness that makes it such a highly sought-after ingredient for lemonades, juices, and jellies. I particularly appreciate this rare species because it is exceptionally easy and rewarding to grow as an exotic container plant.

What’s included: 10 seeds

In the wild, the cas guava grows into a small tree, but stays much more compact when grown in a container on a balcony or patio. It is also very easy to shape with selective pruning. The plant needs the sunniest, warmest spot you can offer it. It has no particular requirements when it comes to soil, as long as it offers excellent drainage. I like to mix high-quality potting soil generously with perlite, pumice, or lava rock to ensure the roots are well aerated and strictly avoid waterlogging. It needs plenty of water in midsummer, but the top layer of soil should always be allowed to dry out slightly before watering again.

As a tropical plant, this guava species cannot tolerate frost at all. Once temperatures consistently drop below 10 degrees Celsius in autumn, it must be brought indoors. I overwinter my plants in the brightest place possible at a cool 10 to 15 degrees Celsius. During this time, watering is reduced considerably and fertilizing is stopped completely.

The fruit is ready to harvest when the skin turns light yellow and yields to gentle pressure. Because of its intense acidity and slightly resinous note, eating it raw is only for the truly hardy. The cas guava really shines when processed: puréed and strained to remove the hard seeds, the pulp mixed with ice water and sugar makes the traditional “Fresco de Cas”—an exceptionally refreshing summer drink. Thanks to its naturally very high pectin content, the pulp sets almost by itself and is perfect for exotic marmalades that slice cleanly.

Botanically, Psidium friedrichsthalianum belongs to the large myrtle family (Myrtaceae). Its native range extends across the tropical regions of Central America, from Honduras through Nicaragua to Costa Rica. There, it grows wild in the warm, humid lowlands and is cultivated in nearly every home garden as a prized plant for making everyday drinks.