The tradition of celebrating Midsummer...
...with poles adorned with leaves also occurs in Sweden and along the southwest coast of Finland. Sometimes the poles are called May poles but in Åland and in the southwest coast of Finland they are called Midsummer poles. The May poles’ and Midsummer poles’ external appearance differ.
Celebration of Midsummer is one of the best cherished traditions in Scandinavian Islands. Its origin is unclear – according to some it is the remains from an old fertility cult while others say that the celebration is a continental custom that came to the Nordic countries in the end of the 1400’s. Oldest of the Midsummer traditions is the adorning of a pole, or “majande”, with leaves, twigs and small trees, of gates, stairways, churches and boats. The oldest documentation of this leafy decoration is from 1670.
Nice blog by Kate Reuterswärd about how to celebrate midsummer in Scandinavia..