Not sure about the ones mentioned in the article, but for the kind I'm used to (i.e Bäsk) in Sweden it's a given.

In our family it's generally been a tradition to go out in the night of August 24th each year to pick some wormwood, and then infuse some plain alcohol with it to have for the coming months. We generally don't leave it in as long recipes call for though, 24h instead of multiple days so the taste is a bit milder.