Choosing the fastest-growing flowers in Florida includes determining which flowers are best adapted to Florida's climate and those that are naturally rapid growers. Florida's climate varies from region to region, with subtropical to tropical climate, instances of freezing temperatures further north and cooler winter night temperatures throughout the state as well as warmer autumn and summer nights. Humidity is high and heavy rain occurs during warmer months.
Dwarf snapdragons (Antirrhinum majus 'Tahiti') are among the fastest-growing annual flowers in Florida. Blooming in a wide array of color options, flowers are available in maroon, yellow, red and orange hues with green to reddish stems accompanying darker blossoms and light green foliage accompanying lighter flower blooms. Flowers may rebloom once, first blooming in April; cut dwarf snapdragons back once the first bloom colors have lost intensity. Thriving in full sunlight, dwarf snapdragons prefer moist soil; tolerances include slightly alkaline or acid soil, sand, loam and clay. These fast-growing plants reach a height of 6-to-15 inches with a spread of 6-to-12 inches. Dwarf snapdragons are hardy in USDA Hardiness Zones 7 to 10, but you can plant them any region.
One of Florida's fastest growers, marigolds (Tagetes spp.) are well suited for planting in Florida's climate. Marigolds are annual plants with full flower blossoms in combination or solid orange, maroon, cream, red or yellow hues with herbaceous green foliage that often releases a strong odor. Flowering from summer through fall, marigolds thrive in full sun and prefer moist, well-drained loam soil; avoid wet sites. Marigolds grow to a height of 6 inches to 4 feet and a width of 6 inches to 3 feet. Hardy when planted in zones 9 to 11, marigolds are widely planted in all regions of the United States.
Pentas plants (Pentas lanceolata) are tall-growing perennials with a fast growth rate well-suited to the Floridian landscape. Displaying an abundance of butterfly-attracting clustered flowers in hues of lavender, white, pink or red, the semi-evergreen foliage is green with tiny hairs. Bloom time is during the spring and summer months. Thriving in partial sun to partial shade, pentas prefer fertile, moist, well-drained soil but tolerate many types of soil, including clay and sand as well as an acid pH. Well-maintained pentas will rebloom during Florida's warmer weather. Pentas grow to a height and width of 2-to-3 feet. Plant pentas in zones 8B to 11.