Ferns 2. A view of thicket of ferns in a forest. Variety of green colors. The summer season. In Slavic folklore, ferns are believed to bloom once a year, during the so called Ivan Kupala night - the feast of St. John the Baptist, celebrated around the time of the summer solstice. Anyone who sees a "fern flower" is thought to be guaranteed to be happy and rich for the rest of their life.