A clump-forming, tall, water-loving, fast growing, dioecious, forest understorey, climbing palm. Not known in cultivation, common in the wild. It has spiny, brown stems, 20 m. (66 ft.) tall, 5 cm. (2 inch) diameter with no obvious leaf scars, and large segmented, pinnate (feather) leaves, 2 m. (7 ft.) long, 0.6 m. (2 ft.) wide, light green above and beneath. Flagella absent Cirri present.
Calamus formosanus can tolerate close to freezing conditions. But low temperatures are best avoided. It naturally occurs in wet rainforest or seasonally wet forest in low montane locations. In this type of natural environment temperature fluctuations are slight, and this palm prefers a constantly cool or mild climate with little temperature difference between day & night, and Summer & Winter. Under extreme cold conditions we recommend you keep this palm as dry as possible, and well wrapped up.
Stems clustered, to 20 m long and 5 cm diameter (with leaf sheaths); leaf sheaths yellowish-brown, densely covered with flattened, yellowish, upward-pointing spines to 2 cm long; knees prominent, swollen, spiny; ocreas short or absent; flagella absent; petioles short or absent; pinnae 18-19 per side of rachis, broadly lanceolate, irregularly arranged (regularly arranged on young plants), distantly spaced 5-8 cm apart; cirri present. Inflorescence bracts tightly sheathing; yellowish-brown.
This palm is widely known as Calamus quinquesetinervius in Taiwan.
Widely distributed in lowland to montane rainforest, to 1000 m elevation.