The taxon belongs to the group of Allium cupani (Brullo et al. 1997).

This species is endemic to Greece. It has been found in only one or possibly two localities, but is treated as uncertain in one of these localities (area of occupancy and extent of occurrence are both best estimated as 4 km²). Its known locality is in an area threatened by development. The population is small and there is an actual and projected continuing decline in the quality and extent of the habitat. Therefore the species is listed as Critically Endangered according to criterion B (CR B1ab(iii)+2ab(iii)).

This species has been described from the coastal area south of the town of Karystos in the southern part of the island of Evvia (Greece). An additional locality has been recorded on Skyros island, western Aegean (Trigas et al. 2021), but the plants from Skyros have some morphological differences compared to the original description of Allium karistanum. The occurrence of the species in Karystos area was confirmed during September 2023 (Nikolopoulos and Trigas unpublished data) for the first time after the type gathering in 1992. The area of Mt. Kochilas on Skyros island was also revisited during 2023 but the species was not found. The record from Skyros is treated as uncertain and is not included in this assessment.

This species is known only from one or possibly two localities: the type locality in southern Evvia island and possibly the island of Skyros, although the identification of the plants found here is uncertain and thought probably to represent a different species. Efforts to rediscover the species at the type locality after its description were fruitless until 2023, when the species was rediscovered in littoral rocks SW of Karistos. The population of Karistos numbers 81 mature individuals. The bulbs of the species form clusters, so additional vegetative individuals occur in this area. The area of Mt. Kochilas on Skyros island was revisited during 2023 but no individuals were found.

The plant occurs on a rocky coast on small, skeletal flats covered with thin layers of sand and clay, on crystalline schist, in full sun. It forms part of the communities of Xerophytes and Centaurea spinosa and Sarcopoterium spinosum. The bioclimate is subhumid with warm winters.

The area where A. karistanum grows in Karistos suffers intense pressures because of tourism and urban development (Trigas 2003). All known individuals grow within a small area of ca 500 m², located by the sea. A small scale disturbance of its natural habitat (e.g., construction of a house or a road) could drive the population to extinction. In Skyros, where the identification of the plants is uncertain, the area from which it was reported is difficult to access by humans, but it is under pressure from overgrazing, especially because of trampling by the animals.

This species is not utilized.

There are no conservation actions targeted to the species and its biotope is not within any type of protected area.