It was customary in Britain and Europe on St John's Eve (June 23), to gather certain herbs, such as St John's wort, vervain, trefoil and rue, all of which were believed to have magical properties. St John's wort (Hypericum perforatum) does, in fact, have scientifically proven anti-depressant qualities. Drinks were brewed from it to cure madness, sciatica, epilepsy and paralysis. The salve made from the herb cured wounds from spears and swords - or, so it is said.
Flowers of St John's wort used to be collected in Britain and Europe on St John's Eve (tonight) and worn on the body or hung over doorways as protection against witches. It was also placed near windows as witches can look in to cast a spell. Even in recent times the people of the Landes district of France would make crosses of wort on their doors.
In Britain, one old custom was for a maiden to pick a sprig of St John's wort and wear it in her bosom until Christmas, by which time the man who was to be her husband, and he alone, would see it and take it from her.
In ancient Latvia, Jani on June 23 was the year's most important festival and it, too, was a celebration of the Summer Solstice. In preparation, everything in the town, including buildings and livestock, was decorated with garlands of papardi (ferns) and janu zali (John's grass). Children traditionally went into the woods on Jani, searching for the fern blossom (like a 'snipe hunt' in North America, since the fern blossom does not exist, or else this was St John's wort) which supposedly bloomed only at night on Jani. Searching for, and theoretically finding, the fern blossom brought good luck.