This native wildflower is found across most of the state, except for the western panhandle. I enjoy seeing the white-topped flower clusters blooming in mesic flatwoods here in south central Florida in the fall. Butterflies, including Malachites, Ruddy Daggerwings, and Julias, very much enjoy nectaring at the blossoms, as do bees and hummingbirds. For this reason butterfly gardeners plant this species. There are two other native Ageratina species that grow wild in north Florida. One of them, A. altissima, the White Snakeroot, was formerly a well known medicinal, although its toxicity should be strongly noted. I would not be surprised if the Hammock Snakeroot is also toxic, so never ingest it. Also, it is listed as "rare" in south Florida, so leave it be in the wild. Another related species, not found wild in Florida, is A. pichinchensis, a mostly Mexican species, known as Axihuitl, aka Snakeroot. It “is a traditional Mexican treatment for superficial fungal infections of the skin. The plant extract contains encecalin which has activity to inhibit and kill the fungus. Studies have compared its effectiveness in treating toenail fungus with ciclopirox.” This makes me wonder if any of our native Ageratinas contain fungus-fighting encecalin.
CAUTION: It is listed as "rare" under IRC south Florida status, so never harvest in the southern part of the state. The Florida Wildflower Foundation writes, "the plant is poisonous to both humans and livestock if ingested." A similar species that grows in north Florida is also toxic, A. altissima, the White Snakeroot, causes “milk sickness”, a serious disease of the 1800s in the central US. “Weakness and nausea may result from drinking the milk of cows that have grazed on White Snakeroot. Abraham Lincoln's mother is thought to have died from this "milk sickness." Further symptoms include severe vomiting, tremors, liver failure, constipation, delirium and death.” 
WILDLIFE: Stephanie Sanchez writes, "It is an excellent fall/winter nectar source."  Flowers attract many butterflies including Malachites, Monarchs, Zebra Longwings, Ruddy Daggerwing, and Julias. Cultivated by native plant / butterfly gardeners.  Roger Hammer writes, "small butterflies visit the flowers, especially crescents, blues, hairstreaks, and skippers."  The flowers are also attractive to bees and birds. 
IN THE LANDSCAPE: "Hammock snakeroot makes a nice low shrub border, but also works well in naturalistic plantings and in mixed beds." 
NATIVE TO: Georgia [in just three counties in the southeasternmost part of the state]  and Florida [most counties, except many in the panhandle.].
IRC SOUTH FLORIDA STATUS: Rare. 
HABITAT: Mesic flatwoods and mesic hammocks.  Dry sandhills.  Also "upland mixed woodlands, and along roadsides and stream banks." 
FIRE ECOLOGY: Natureserve writes, "A. jucunda is an associate species of longleaf pine and wiregrass communities that are dependent on periodic fires to maintain the integrity and productivity. Fire suppression can cause ideal habitat loss and therefore a loss of populations of A. jucunda." 
DESCRIPTION: Flowering herbaceous perennial.
- HEIGHT: 1-3 feet or more.
- STEMS: Erect.
- LEAVES: Opposite, pointed, glabrous, triangular, with crenate / serrate leaf margin. Lance-shaped. "Leaf Pubescence: Glabrous." 
- FLOWERS: "It is yet another member of the Eupatorieae tribe of the Aster family, which means its flowers consist of only disc and no ray florets. Its disc flowers are tubular."  Flowers white, tiny, in flat-topped clusters. Appearing "late summer to early winter."  Roger Hammer lists is as blooming from September through January.  "Summer through early winter" in Florida.  September through January.  "October through December."  They may have "a hint of a purple-pink color depending on which way the light hits them." 
NOTE: This genus was recently divided from Eupatorium.
SYNONYM: Eupatorium juncundum.
RELATED SPECIES: There are two other species of Ageratina found here in Florida.
SIMILAR SPECIES AND THEIR MEDICINAL PROPERTIES: Two other species within the genus grow wild in the northern part of the state, A. altissima and A. aromatica.
- A. altissima, the native WHITE SNAKEROOT, is discussed in Florida Ethnobotany, by Austin. It was known as Noota [tooth] ikheesh [medicine] by the Choctaw and Chickasaw. The Chickasaw and Choctaw chewed the root and held it in the mouth for toothache. [Austin] “Root tea used for ague, diarrhea, kidney stones, and fever. Root poultice used to treat snakebites.”  “Smoke from burning green leaves used to revive unconscious people.”  It grows in 5 central panhandle counties as well as in Georgia. CAUTION: This species causes “milk sickness”, a serious disease of the 1800s in the central US. “Weakness and nausea may result from drinking the milk of cows that have grazed on White Snakeroot. Abraham Lincoln's mother is thought to have died from this "milk sickness." Further symptoms include severe vomiting, tremors, liver failure, constipation, delirium and death.”  Altissima: "The plant contains tremetol, a complex alcohol, and glycosides. These toxins cause a fatal disease known as 'staggers' in cattle. The toxin can be passed through the milk and has caused fatalities in humans who have drunk affected cow's milk." 
- A. aromatica, the LESSER SNAKEROOT.
SIMILAR SPECIES IN FLORIDA: Mikania species, which are vines, may appear similar from a distance.
ANOTHER AGERATINA SPECIES: Another species, not found wild in Florida, is A. pichinchensis, a mostly Mexican species, known as AXIHUITL, aka Snakeroot. It “is a traditional Mexican treatment for superficial fungal infections of the skin. The plant extract contains encecalin which has activity to inhibit and kill the fungus. Studies have compared its effectiveness in treating toenail fungus with ciclopirox.”
- HARDINESS: USDA zones 8-11. 
- LIGHT: Sun to partial shade. It does well in "high pine shade." 
- WATER: It does well in moist, but well drained soil.
- SOIL: It prefers well drained soil. 
- DROUGHT TOLERANCE: "It cam handle short periods of drought once established." 
Mesic Flatwoods. Mesic Hardwoods
Ease of growth
Sources for acquiring
The Florida Wildflower Foundation writes, "seeds are available through the Florida Wildflowers Growers Cooperative. Plants are often available at nurseries that specialize in native plants." 
 Medicinal Plants of the Northeast, Brandeis University
 Florida Wildflower Foundation's Blog
 Natureserve via Wikipedia
 Illustrated Flora of West Central Texas, via Plants for a Future
 Central Florida Wildflowers: A Field Guide to Wildflowers of the Lake Wales..., by Roger Hammer