Bur marigold - Bidens mitis
This is one of two almost indistinguishable Bidens species that are native to Florida. The other species is Bidens laevis. Bur marigold occurs throughout Florida. It is found in open, marshy areas.
Bur marigold has conspicuous bright yellow, astor-like flowers. The plants typically grow to about 2-1/2 feet tall. Flowers are 2 inches wide and usually have 8 petals. Flowers grow at the tops of the plants and can occur in profusion.
Bur marigold leaves are variable in size and shape but are usually lance shaped, sometimes with points. Leaves often have teeth on the margins, or they may be deeply lobed. They are arranged oppositely along the stem.