Name and habitat
Acanthocereus lempirensis was described in 2023 during surveys near Montaña de Celaque National Park. POWO accepts this name. The species is endemic to Honduras and occurs on limestone cliffs and steep slopes in the department of Lempira. The description reports elevations of 1100–1560 m and tropical deciduous or subdeciduous forests containing oaks and pines. [Vega et al. 2023, pp. 1–2, 4, POWO 77327925-1, 12.10.2026] [2-WWW]
Juvenile and adult stems
The shrub usually branches from the base and produces tuberous roots. Living stems are glaucous green. Juvenile stems have 6–10 ribs and reach 2.6 cm in diameter at their widest point. Developed stems have 3–5 ribs and are usually 3–6 cm in diameter, exceptionally 7 cm. This structural change is an important part of plant development. [Vega et al. 2023, pp. 2, 4]
The spines of developed stems are rigid, needle-like and conspicuously swollen at the base. Each areole usually bears 5–8 spines, exceptionally nine. Their length is generally 1–3 cm. They are beige or grey with a reddish-brown tip. The description treats them as poorly differentiated into central and radial spines. [Vega et al. 2023, pp. 4]
Pink flowers open at night
The flowers are usually 8–10 cm long, exceptionally 11 cm. Their pink inner tepals broaden towards the tip, and the apices are rounded or shallowly notched, with finely lacerate margins. This combination helps distinguish the species from A. chiapensis, whose tepals are cream-white and narrower. Flowering occurs from March to June. The flowers are fully open from midnight until the early hours of the following morning. [Vega et al. 2023, pp. 4, 6, table 1]
Fruiting
The fruits ripen from June to July. They are red, nearly ovoid or obovoid, 6–7.5 cm long and 4–5.5 cm wide. They open through a longitudinal split and contain red pulp. Local people eat them as sweet-sour fruits called tunas. The description also records large, glossy black seeds. [Vega et al. 2023, pp. 4]
A small population on limestone slopes
The 2023 study recorded approximately 150 plants within about 500 hectares of fragmented forest. Expansion of cultivation and grazing affect the habitat. The authors proposed the Critically Endangered category, CR. This assessment concerns the population known at that time and was presented in the original species description. [Vega et al. 2023, pp. 5]