Trollius europaeus
A yellow, ball-shaped flower whose yellow, petal-like sepals stay folded over one another. It grows in groups in damp meadows and mountain pastures, up to the alpine zone. Small insects slip inside the ball to feed and pollinate it.
At the end of May, in a damp mountain meadow, yellow balls sway at the tips of their stems, packed in clumps. Not one of them opens, even in full sun: the globeflower keeps its flower closed like a bud.
What look like petals are coloured sepals. According to Info Flora, there are 10 to 15 of them, bright yellow, curved towards one another until they form a sphere. According to a study published in 2015 in the journal Ecology and Evolution, this ball reaches 5 cm across and holds some thirty carpels, a host of stamens and small parts that produce nectar. The stem, upright and unbranched, measures 10 to 50 cm. The leaves are cut into deep, toothed lobes, like a hand. Among its German names, Info Flora cites “Ankebälli”, the little ball of butter.
Info Flora reports it throughout Switzerland, in damp meadows and pastures, mainly in the montane and subalpine zones, more rarely in the hills or in the alpine zone. It is found in marsh-marigold meadows, mown mountain meadows and cool limestone grassland. Elsewhere, this arctic-alpine plant lives in northern and central Europe and in the mountains of the south.
A population flowers almost all at once, for two to three weeks, and each flower lasts about a week, longer in rainy weather. As it hardly ever fertilises itself, the globeflower needs insects, above all small flies of the genus Chiastocheta: seven species in Europe, which breed only in its fruits. They slip into the ball to eat, mate, lay eggs or shelter from the cold, and pick up pollen on the way. Their larvae devour some of the seeds, then overwinter in the soil. The plant was long thought to depend on these flies alone. But in Poland, the 2015 study followed populations that had lost them: these globeflowers reproduced about as well, and other insects, including small beetles, carried pollen there.
The Red List does not consider it threatened across the country, but vulnerable on the Swiss Plateau. The Confederation does not protect it; seven cantons do, fully in Basel-Landschaft, Schaffhausen, Solothurn and Thurgau, partially in Jura, Zurich and Appenzell Innerrhoden. It is also one of the characteristic species named in the Environmental Objectives for Agriculture.
Sources: Info Flora, species account (after Flora Helvetica); T. Suchan et al., “Asymmetrical nature of the Trollius–Chiastocheta interaction”, Ecology and Evolution, 2015.
