Sometimes, they come dressed as eye-popping purple blooms that could complement (or even outdo) your prized perennials — if only they weren't aggressive. Purple deadnettle, bull thistle ...

unlike the leaves and unlike bull thistle and European marsh thistle pink, white, or lavender-colored flowers with flat bracts and pointed tips that bloom in June seed are fluffy, white tufts of hair ...

Bull thistle, a member of the Asteraceae family ... although repeated cuts - one early season before flowers bloom, and one late season - will be needed to suppress the plant (be sure not to mow ...