Nepenthes eustachya

Species of pitcher plant from Sumatra

Nepenthes eustachya /n//ᵻ/'/p//ɛ//n//θ//iː//z// //juː/'/s//t//æ//k//i//ə/ is a tropical pitcher plant endemic to Sumatra, where it grows from sea level to an elevation of 1600 m. The specific epithet eustachya, formed from the Greek words eu (true) and stachys (spike), refers to the racemose structure of the inflorescence.

Nepenthes eustachya was probably first collected in February 1856 by Johannes Elias Teijsmann on the Sumatran coast near the port town of Sibolga. This specimen, Teijsmann 529, was designated as the lectotype of N. eustachya by Matthew Jebb and Martin Cheek in their 1997 monograph. It is deposited at the herbarium of the Bogor Botanical Gardens along with two isotypes. B. H. Danser did not support this interpretation and instead treated N. eustachya in synonymy with N. alata in his seminal monograph, "The Nepenthaceae of the Netherlands Indies", published in 1928. He wrote:

Plants belonging to N. eustachya were identified as N. alata by a number of subsequent authors, including Shigeo Kurata in 1973,

In 1997, N. eustachya was once again elevated to species rank by Matthew Jebb and Martin Cheek, who noted a number of differences between the two taxa.

Nepenthes eustachya is a climbing plant. The stem attains a length of up to 5 m and a diameter of 0.8 cm. Internodes are cylindrical in cross section and up to 12 cm long. The lid is sub orbicular and lacks appendages. The spur is up to 4 mm long and generally bifid. Nepenthes eustachya usually grows in open, sunny sites on cliff faces and steep slopes at the forest margin. It is restricted to sandstone substrates and often grows on bare rock. Where the species does occur it is common and may form dense clumps, such as those growing beside the road from Sibolga to Tarutung in North Sumatra. It is known to hybridise with all of these species. The conservation status of N. eustachya is listed as Least Concern on the 2006 IUCN Red List of Threatened Species. N. gracilis, and N. sumatrana have been observed.