White-flowered Pricklypoppy - Argemone albiflora

Two species of pricklypoppies are native to Florida. The yellow-flowered one, Mexican pricklypoppy (Argemone mexicana) is common throughout much of peninsular Florida. The white-flowered species (A. albiflora), described in this post is found in the same locations. It is not uncommon to find both along roadsides in full sun and sandy soils.  These are members of the true poppy family.
White-flowered pricklypoppy is an annual with thistle-like foliage. The clasping, very spiny leaves are deeply lobed and the leaves are alternating along the stem. Multiple flower stalks are produced and reach a maure height of about 3-4 feet. The flowers are produced for several months from late spring through summer.  They are quite showy, with broad, frilly petals and bright yellow stamens (the male parts of the flower) in the center.  The pollinated flowers form spiny seed capsules that open at the top. The poppy-type seeds are then released over time as the seed capsules are shaken by wind and rain.
Although the flowers are quite attractive, the very spiny nature of this wildflower limits its attractiveness in a landscape setting. I am not aware that either species of pricklypoppy has ever been offered for sale commercially in Florida. It is extremely adaptable to open sunny locations and would be easy to grow. If you are interested, be careful to limit its spread to only those areas where its prickly nature won't be a problem.

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.

Goldencrest - Lophiola aurea

Goldencrest (Lophiola aurea) is an erect perennial herb native to the central and western portions of the Florida Panhandle. Originally included in the same genus as redroot (Lachnanthes caroliana) there are superficial resemblances between the two, but also significant differences. For one, goldencrest has whitish to brownish roots - not red, and there are also differences in their chemical and pollen structure. Goldencrest, therefore, has been put in its own genus and this is the only species worldwide. It is found throughout the Deep South with disjunct populations being reported from New Jersey and Prince Edward Island. Goldencrest is a species of wet savannas, bogs and ditches where it gets full sun and nearly constant wet soil.

It dies to the ground each winter, and reaches a mature height of 1-3 feet in late spring.  The leaves are small, linear, and less than 1/4 inch wide. Flower heads are produced at the top of the stalk. They are open cymes with the stems and the flower heads covered by white wooly hairs.  The individual flowers are tiny with a yellow crest emerging from the top of the bud. Each of these flower buds ripens to a dry capsule in late summer.

Goldencrest has never been offered for sale commercially in Florida, to the best of my knowledge.  It is a common plant of the open savannas of Apalachicola National Forest (where these photos were taken), in the same types of habitats where pitcher plants, sundews, and grass pink orchids occur. Look for it in late spring.