Green week

Green week (Зелёные Святки, also known as Семи́к – Semik, ukrainian: Зелені Свята) is an ancient Slavic fertility festival celebrated in early June and closely linked with the cult of the dead and the spring agricultural rites. It usually fell upon the Thursday of the Green Week (better known as Trinity Week in Russia and the Whitsuntide week in Britain). Its name is derived from the Slavic word for "seven", because the Green Week was the seventh (sometimes the eighth) week after Easter. The end of Semik inaugurated the celebrations of the Trinity Sunday.

The Rusalki were believed to be at their most dangerous during the Green Week (Russian: русальная неделя), and were supposed to have left their watery depths in order to swing on branches of birch and willow trees at night. Peasant women sometimes hung offerings to appease them. A cross, a magic circle, incense, garlic, wormwood, a pin or poker and verbal charms were used to render the rusalki harmless. Swimming was strictly forbidden, lest mermaids would drag the swimmer down to the river floor.