Sideritis khalkhalica (Lamiaceae: Lamioideae), a new species from Northwest Iran

Sideritis khalkhalica sp. nov. (S. sect. Hesiodia Benth.) is described as a new species from northwest Iran. It appears to be a local endemic restricted to open slopes of marl hills in Khalkhal region, Ardabil province. This species differs from its closest relative, Sideritis montana and S. romana by having stems that are hairy with retrorse hairs, leaves petiolate, ovate to elliptic, with calyx teeth narrowly triangular, corolla white and pollen type balansae. Comparison with similar species, detailed photographs, micro-morphological characters of pollen grains are also provided. Moreover, its protection is recommended and proposed that the new species should be listed as Critically Endangered.