Large groups of unruly teenagers at an Illinois pool and California mall prompted early closures that resulted in arrests, highlighting what experts call a symptom of cultural breakdown.

They say so-called flash mobs are sneaking into apartment buildings at night, taking over community rooms by partying and causing damage.

Space your Flash Mob petunias about 20 inches apart to allow for the showiest display. You will be surprised how quickly you will achieve a solid mass.