Do mold grow in dry conditions?

Yes, but mold may still continue growing with less moisture than what it takes to germinate mold spores(about 60% RH). Mold also tends to release more spores as it dries out which aids in "spreading the colony" so to speak. This is one of the reasons a removal or cleaning of mold is recommended along with preventing the moisture which caused it to grow in the first place. Moisture prevention is #1 but cleaning is also beneficial, especially to those few who may have allergic reactions to the mold.