Gentiana acaulis
The blue gentian of the Alps: a large, deep-blue trumpet flower sitting almost without a stem on a rosette of leaves. It grows in the meadows and pastures of the alpine zone, on acid soils.
On a high pasture where the grass grows short and thin, large bells of an almost midnight blue seem to sit right on the ground. They have no stem to hold them up, or hardly any: this is the trumpet gentian, whose scientific name, acaulis, means “stemless”.
Info Flora also calls it the large calcifuge gentian, or Koch’s gentian. Each flower, borne singly, is a deep-blue bell-shaped corolla that flares into five lobes. Up close, lines of small olive-green dots can be seen inside. The flower stands above a rosette of soft, obovate or elliptical leaves with rounded tips, which reach 10 cm. This intense blue may serve a purpose: according to the Swiss National Park, alpine flowers build up pigments that absorb ultraviolet light, like a sun cream, and a gentian planted in the lowlands would soon turn paler.
As its other name indicates, it avoids limestone. Info Flora reports it in grassland and pastures on lime-poor soils, above all the poor, acid matgrass pastures. It is found from the subalpine to the alpine zone, sometimes lower, in the Alps, the Prealps and, for the Jura, as far as the canton of Bern. Its twin, Clusius’s gentian, occupies limestone grassland and rocks instead.
A perennial, it spends the winter with its buds at ground level, which places it among the hemicryptophytes. It flowers from May to August. Where the two species meet, it crosses with Clusius’s gentian: Info Flora mentions hybrids and intermediate forms, which sometimes make identification tricky.
The species is not threatened in the country, but the Red List considers it near threatened in the Jura. The Confederation does not protect it. According to Info Flora, fourteen cantons do: fully in Zurich, Schwyz, Appenzell Innerrhoden and Thurgau, partially in ten others, including Bern, Fribourg, Vaud, Neuchâtel and Jura.
Sources: Info Flora, species accounts for the large calcifuge gentian (Gentiana acaulis) and the large calcicole gentian (Gentiana clusii); Swiss National Park, document “Anpassung der Alpenpflanzen an ihren Lebensraum”.
