Are dandelions flowers or weeds?

From history, Dandelions are weeds that do not negatively affect town happiness and will eventually mature into dandelion puffs which can be blown away.

So they're weeds, though you don't necessarily have to pull them. You can even transplant them if you pick them before they turn into puffs. A hint to their weedy nature is that they take many more attempts to trample. 3 tramples will kill a flower, it takes more like 8 to kill a dandelion.