Origanum calacaratum belongs to Section Amaracus (Gleditsch) Bentham. It is one of the most variable species of the Section and closely related to O. dictamnus. The name O. calacaratum has been published at least a few days earlier than the synonym O. tournefortii and thus, it has priority (Ietswaart 1980).

This species is endemic to Greece, where it occurs on a range of islands in the Aegean Sea. It is assessed as Vulnerable (VUC2a(i)). Its area of occupancy (AOO) is around 100 km², within an extent of occurrence (EOO) of 18,427 km², and it occurs in at least and 15 locations. Overgrazing occurs in almost all its subpopulations and as a result a decline in the number of individuals has been observed. Additionally, it is also collected from the wild and consumed as herbal tea. The size of one subpopulation (on Crete) was estimated in the early 1990s as around 100 individuals spread on limestone cliffs and vertical crevices, while in 2022 only 35 individuals were found. Moreover, the number of mature individuals in the largest subpopulation is estimated to be around 1,000 and observations in three more subpopulations resulted to a total number of 20, 30 and 35 individuals. Although there are no direct observations for the rest of its subpopulations they are all located on very small islands and thus, it seems unlikely that the population size exceeds 2,000 individuals.

Origanum calcaratum is an Aegean endemic, but it was considered to be an endemic of the island of Amorgos. However, it has been found that it occupies a much wider area. It has been found, besides Amorgos, on the islands Keros, Schoinousa, Iraklia, Anydros, Astypalaea, Ofidoussa, Syrna, Zafora, Chalki and on a single locality on the island of Crete (Sitia, Roussa Ekklisia) (Strid 2022, Antaloudaki 2022, Strid 2016, Karousou 1995).

It is found in around 17 subpopulations mostly on very small islands. There are direct observations and population size estimates for four subpopulations (two on Amorgos, one on Chalki and one on Crete). Three of these subpopulations are heavily grazed and the flowering heads of a large number of individuals was consumed by the herds. Given that grazing exists in the majority of the Aegean islands it is assumed that the same applies for the rest of its distribution. Three of the observed subpopulations have less than 50 individuals, but one subpopulation in Amorgos occurring on vertical cliffs and not grazed at all had around 1,000 individuals. It is estimated that in the rest small islands the population number must be also very low (<50 individuals). In the Cretan subpopulation, which is rather isolated from the other subpopulations, the number of individuals was roughly estimated by the first assessor in early 1990s to be around 100 individuals dispersed on several limestone rocks and vertical crevices. However the second assessor found in 2022 a maximum of 35 individuals restricted on a single crevice (Karousou 2009, Antaloudaki 2022).

This plant grows on vertical crevices and limestone cliffs at an altitude between 50 and 600 m. It flowers from April to October (Antaloudaki 2022, Karousou 1995).

Overgrazing occurs in almost all localities and as a result a decline in the number of individuals has been observed. Additionally on the island of Amorgos it is collected from the wild and dried material is consumed as herbal tea.

On the island of Amorgos the species is collected by the locals and consumed as a herbal tea.

It is found in the Natura 2000 sites GR4220013, GR422002, GR4210009, GR4210011, GR4210026. It is also declared protected by the Presidential Decree 67/81, but it is unknown if any conservation measures are taken. However, it is desirable to keep material in a Genome resource bank. Some research on the population  size and trends is also needed.