Florida Tasselflower - Emilia fosbergii

Florida tasselflower (Emilia fosbergii) is a common non-native lawn weed, but an attractive one that is found in nearly everyone's landscape within peninsular Florida. It is not likely to be found in extreme north Florida or the Panhandle.  This is a widely distributed plant worldwide, and is reported from much of the West Indies, Mexico south to parts of Brazil, many western Pacific islands, tropical Africa, and parts of Indonesia.
Florida tasselflower is an annual member of the aster family. It comes up each year from the copious seed shed from the year before. A cluster of basal leaves forms early. They are diamond  shaped with a toothed margin and a "wing" along the leaf stem (i.e. the petiole).  A central floral stem is then produced that can reach 2-3 feet tall. The leaves along the stem do not have petioles .  Flower buds occur at the top of each stem. They open from late spring to fall on open heads. The petals are crimson to deep pink in color.  A closely related non-native species, lilac tasselflower (E. sonchifolia) has lilac-colored flowers - not crimson or pink.
Florida tasselflower produces a great many flowers and, when ripe, they produce a great many dandelion-type seeds. The fluffy appendages, attached to each seed, are designed to catch the wind and waft each seed far away from the parent plant.  If you allow your plants to go to seed, you will get a great many more each season. Florida tasselflower is extremely adaptable. It does very well in open sunny, disturbed locations as well as sites that are mostly shady. As a member of the aster family, its flowers draw pollinators. 
I choose to leave a few of these "weeds" alone each year in the corners of my landscape for the bees and butterflies, but I weed them aggressively in the other parts of my landscape. If you leave it completely alone, it will take over your landscape and likely become a nuisance.