Translation:On Midsummer we put seven different flowers under our pillows.
If you're considering this paganism, then it's alive and well all over the world because there are plenty of equivalently odd superstitious beliefs of about the same level of 'worship' throughout the world (see for example the English phrase 'knock on wood', or all the people who believe that breaking a mirror is bad luck).
It seems that Duo doesn't like "lay" for "lägger" (or at least, it rejected On midsummer we lay seven different flowers under the pillow and accepted On midsummer we put seven different flowers under the pillow). Is there a reason for that, or just a matter of a less-common wording not being added to the database?
Does English need to have the plural pillows here? In my native dutch I could say "our pillow" and everyone would know I'm speaking of the pillows of each of us, and not 1 pillow we all share. That's why I struggle to give the right translation each time this sentence comes up ;)