Cyrtosperma: The swamp giants of the Pacific

Aroids of the genus Cyrtosperma are still almost unknown in Europe, but they are beautiful and very easy to care for. They are gigantic, side-shoot-forming herbs that can grow to about 3 meters tall, eventually forming a clump of large crowns.

Cyrtosperma grows in the seasonally monsoon-flooded forests of Papua New Guinea, Indonesia and surrounding islands. They can even tolerate brackish water. They have an upright growth habit with vertically borne leaves, similar to some Alocasia.

The leaves are pointed and arrow-shaped with the posterior lobes slightly exceeding the anterior ones. They form a very thick rhizome which can also grow over 2 meters long and is cooked in its native regions. Old rhizomes can weigh over 100 kg, making it the world's largest vegetable.

Botanical description

Cyrtosperma johnstonii is known only from a wide distribution in cultivation, and is said to have been introduced from the Solomon Islands. There are no collections which can be said with certainty to be of this species from wild plants. Buka Island lies at the northwestern end of the Solomon Islands chain, where there has been a plant labelled 'Caladium', which is de facto Cyrtosperma johnstonii. This means that the species has in fact come from this geographical area.

Cyrtosperma is a small genus of flowering plants native to Southeast Asia and the Pacific Islands. The genus includes robust, marsh-dwelling geophytes with creeping rhizomes and spiny petioles. These species bear bisexual inflorescences and have been taxonomically refined into a core group centered in New Guinea.

The petioles can grow up to 2.5 metres long and are irregularly and obliquely spotted in white, green, brown and pink, heavily armed with spines that merge into oblique combs. The midribs are bright pink in young specimens, later with the leaf blades mottled reddish-brownish underneath and the midribs green to brown.

Care

Cyrtosperma johnstonii grows large with heights of 2-4 meters. Give the plant plenty of space and a strong support as it matures.

As a potted plant, it thrives in consistently moist soil and can even withstand flooding. Keep the soil consistently moist or even standing in water, especially during the growing season.

Place in bright, indirect light. The plant thrives in warm, humid conditions that mimic its natural habitat in the swamps and floodplain forests of the Pacific region.

Use rich, loamy soil that can hold moisture. The plant appreciates high humidity and warm temperatures year-round. Fertilize regularly during the growing season to support vigorous growth.

Image credit: Peter Schmitz , Cyrtosperma johnstonii (NEBr.) NEBr., 13.08.2023
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