Name: Sandy B. Ford River Twp, Michigan UP (Zone 4b) (Zone 4b-maybe 5a)
Maybe you could just cover the geraniums with something -- like an upside-down bucket ? and then spray around them. (I would suggest using a weed killer that doesn't have 'soil activity' - like Roundup, for instance).
“Think occasionally of the suffering of which you spare yourself the sight." ~ Albert Schweitzer C/F temp conversion