Polygala calcarea

A perennial from the Polygalaceae family, this limestone-loving milkwort is confined to the limestone grasslands and hillsides of Western Europe, from southern England to the Iberian Peninsula. These photographs were taken in the Picos de Europa, a limestone massif in northern Spain, where it colonizes short grasslands and rock crevices at about 800 to 1,800 meters, on well-exposed limestone substrate.

It forms prostrate and dense tufts, very low, rarely beyond 5 to 10 cm in height. The foliage is evergreen, composed of small oval to spatulate leaves, bright green, tightly along the reclining stems. An immediately noticeable distinctive feature is the arrangement of the basal leaves in flattened rosettes, significantly larger than the cauline leaves — a characteristic that distinguishes it from Polygala vulgaris.

The flowers, of an intense and deep blue-violet, are gathered in short and dense clusters that seem to almost emerge directly from the foliage. The two petaloid wings frame a well-developed white-fringed keel, creating a striking contrast visible in the photographs.

In its natural habitat, its flowering extends from April to June depending on altitude and exposure. In cultivation, it generally blooms in May-June.

It requires a lean limestone soil, perfectly drained, in full sun exposure. Appreciated in limestone rock gardens, it is nevertheless reputed to be capricious to maintain sustainably outside its natural substrate, probably due to its specific mycorrhizal associations.