Tufted perennials, seldom stoloniferous. Stem trigonous to terete, mostly smooth. Leaves from ¼ to overtopping stem length, basal sheaths often conspicuous, hard and stiff, or soft and thin, blades from filiform, nearly unifacial to keeled, 3.5 mm wide; ligule present. Inflorescence from spike-like (called spike below) to small paniculodium. Flowers unisexual; sometimes distal part of inflorescence containing staminate and proximal part pistillate flowers. Utricles (prophylls) from open to nearly completely closed; rachilla with or without staminate flowers. Stamens 2-3, stigmas 2-3.
Identification of Kobresia species requires a special attention to be given to the inflorescence structure. The inflorescences may be clearly branched, i.e. the lateral branches are definitely elongated forming thus a small paniculodium. However, as the female flower is always, even in spike-like inflorescences, only born in the axil of a prophyll, i.e. in the axil of the first leaf of a lateral branch, an inflorescence containing female flowers is by definition not a spike but a multiple spike. The lateral branch can, in Kobresia, always be detected within the utricle (prophyll).
Nevertheless, for practicel purposes, an inflorescence is being called a spike, when even on the lowest lateral branch is but one utricle, and a multiple spike when the lateral branches are elongated and bear more than one utricle; exceptions are indicated (e.g. K. schoenoides). The lateral branch or rachilla may remain within or extend from the utricle.
Kobresia species, and Carex, are characterized by the unisexual flowers and by the utricle (prophyll) immediately surrounding the gynoecium. The term utricle is used below irrespective whether margins of the prophyll are more or less fused or open. In Kobresia the transformed prophylls, utricles, do not have a clearly differentiated beak and are not or not completely closed as in Carex, especially in the basal parts of the inflorescence. Kobresia differs from Carex also in having an axis extension, rachilla, which extends from within the utricles; the rachilla bears one or more male flowers, or is sterile and then often remains within the utricle.
Also the use of the term glume requires in Kobresia (and Carex) an explanation. Normally glume refers to a scale (leaf) supporting the flower. In case of unisexual male flowers the application is clear. Application in case of the female fowers, however, born in the axil of prophylls or utricles is not the same; here the glume refers to a glume-like bract supporting a reduced lateral branch, rachilla. Nevertheless, in the following the term glume is used for these glume-like bracts. The bract again, by definition, refers to a (mostly) green leaf with more or less expanded blade supporting an extended lateral branch as e.g. in K. laxa.