Trollius europaeus is commonly known as globeflower. This northern temperate species is native to Europe and western Asia. Typical habitats include wet pastures, scrub, and woodlands, often in association with alkaline and limestone soils.
It is characterized by near-spherical lemon-yellow flowers (hence the common name) that range between 2.5-5cm in diameter. Within the native range of the species, plants bloom between May and June. It is uncommon to see the flowers fully open; fully- to partially-closed flowers are more typical. How do these get pollinated? Small anthomyid flies (Chiastocheta spp.) enter between the enclosing sepals to access the inner whorls of the flowers. Once inside, the flies feed, rest, and mate. Occasionally, they depart for another flower and end up cross-pollinating the new destination in the process. The flies lay their eggs on the carpels, and the hatched larvae consume some of the developing seeds. The seeds ripen quickly enough that some are able to fully develop and disperse. The Botanical Society of Britain and Ireland has an excellent factsheet about Trollius europaeus (PDF) that includes additional details about pollination, habitats, and threats.
Like several other Ranunculaceae, Trollius europaeus contains a poison called protoanemonin that is used to protect the plant and deter browsers by being bitter-tasting and blister-inducing. In the past, it has been used medicinally as a purgative and rubefacient.