Prone to hybridisation and back-crossing, the ±30 species of Sesleria are a taxonomic tangle of poorly differentiated species, forms and ecotypes. For the urban specifier, however, the genus is a rich vein of compact, low-maintenance taxa.
The striking yellow-green S. autumnalis is widely used, and so too is the blue-green S. nitida. Rather less common is the plant available as Sesleria caerulea, whose strap-like leaves are blue-green above, and dark green below, giving a remarkable and attractive two-tone effect (slate-blue early-spring flowers are an incidental benefit). Forming evergreen knee-high clumps and tolerant of a variety of soils, the rounded
form is retained throughout the year, ideal as ground cover or matrix. Maintenance includes raking out dead foliage and flowers and a late-winter trim.
Confusingly, however, the species just described, found in moist habitats across Eastern Europe south of Sweden and which probably represents most plants available commercially, has been reassigned to Sesleria uliginosa. The plant now scientifically recognised as S. caerulea (syn. S. albicans) is not widely available but offers significant promise for continental European urban contexts: a robust, upland species that roots deeply and quickly into unstable screes (often limestone, though its Ca requirement is not great), hence potentially valuable in technical gravel or stone-mulch plantings. It is tolerant of light shade (colonising beech woods).
Desiccation-tolerant leaves enable it to remain attractively verdant in hot, droughty conditions (unusual for a cool-season grass), and it seems able to recover from water deficits that would devastate other grasses. Anecdotally, plants apparently dead in extreme summers have miraculously revived in the autumn.
There is ample scope for establishing a commercial basis for this promising species, sometimes offered as S. albicans. But specifiers beware–the discrepancy between scientific and trade nomenclature is unlikely to be resolved, so be sure of your material!
By Martin Deasy is a tutor on the RHS Mhort. He also runs his own landscape design business.