(CNN) — In the Northern Hemisphere, the summer solstice has a history of stirring libidos, and it’s no wonder. The longest day of the year tends to kick off the start of the summer season and with it, the harvest. So it should come as no surprise that the solstice is linked to fertility — both of the vegetal and human variety.

“A lot of children are born nine months after Midsummer in Sweden,” says Jan-Öjvind Swahn, a Swedish ethnologist and the author of several books on the subject.

Midsummer is the Scandinavian holiday celebrating the summer solstice, which this year falls on June 21. Swedish traditions include dancing around a Maypole — a symbol which some view as phallic — and feasting on herring and copious amounts of vodka.

“Drinking is the most typical Midsummer tradition. There are historical pictures of people drinking to the point where they can’t go on anymore,” says Swahn. While the libations have a hand in the subsequent baby boom, Swahn points out that even without the booze, Midsummer is a time rich in romantic ritual.

To read more: “Summer Solstice: It’s All About Sex”