Aprill 2002
Airboat storage yard near the junction of Krome Ave. and highway 41 (Dade Corners)

Melaleuca, Melaleuca quinquenervia, has infested much of sourth Florida.  This includes the
pine flatwoods, hardwood bottomlands, cypress forests, freshwater marshes, sawgrass prairies,
farmlands, urban areas, and even mangrove communities.
These incredible and adaptable trees grow to a height of 80' and grow in terestrial and
completely aquatic habitats into immense forests.
It was introduced to Florida as seeds sent from Sydney, Australia in 1906.
In 1941, the United States Army Corps of Engineers planted Melaleuca trees on levees south of
Lake Okeechobee for erosion control.  Now Melaleuca infests thousands of acres from here to
Big Cypress in the west to Biscayne Bay in the east.
So why is Melaleuca so bad?
It is eliminates native vegetation and drains wetlands: many of the sawgrass prairies are being
converted to Melaleuca forests and if left unchecked the "river of grass" will become the "river of
trees"!
An economic study commissioned by the Florida Department of Environmental Protection
stated that the unbridled spread of melaleuca would severely restrict use of south Florida's parks
and recreation areas by local residents and tourists. The potential loss to florida would be in the
tens of millions of dollars.
Why has Melaleuca done so well in south Florida?
Note the sprout on this Melaleuca tree stump.
An epicormic a shoot is one that arises from latent or adventitious buds.  Such sprouts often arise
from Melaleuca tree stumps.
Melaleuca thrives in south Florida due to the similarities with its native habitat in Australia. The
climate of south Florida is sub-tropical as is its native habitat in Australia. Both areas are located
at ~26º latitude (26ºN in Florida and 26ºS in Australia) and experience wet summers and dry
winters with frequent fires. The role of fire is important in the biology of Melaleuca. It has several
attributes that allow it to thrive in fire-maintained wetlands. The ability of Melaleuca to withstand
fire allows it to outcompete fire-intolerant species. The thick, spongy bark helps in retarding the
effects of fire.
Fire rarely kills Melaleuca trees and epicormic sprouts often form on the trunk that promote more
growth.  Like some pine trees, Melaleuca releases seeds when fires occur. So fire is vital for its
survival.  
The hydroperiod and the peat soils are also ideal for it.
Melaleuca seems to thrive best in areas of peat soils and shortened hydroperiods, which
encourage germination and growth of seedlings. Resulting infestations are hypothesized to dry out
wetlands because of an increase in evapotranspiration rates. This hypothesis is based on
measurements of transpiration rates across the surface of individual leaves and an estimate of total
leaf area in mature melaleuca stands.
Studies of whole trees or entire forests are lacking, but the south Florida Water Management
District (SFWMD) hopes to use such methods to test this hypothesis in the near future: Melaleuca
stands may alter wetland hydrology by changing soil topography.
How do we extirpate Melaleuca from south Florida?
One of the newer methods is a three step strategy: One, cut the tree down, Two, burn it to make
sure it is dead.  Three, poison it with herbicide to prevent epicormic sprouts.
It is important that Melaleuca is controlled so that it doesn't decimate the entire Everglades.
Melaleuca is may not be threat to the Gulf Coast of Louisiana and eastern Texas due to the
fact that Melaleuca seedlings are killed by freezes.  Frost probably limits significant amounts of
natural regeneration of Melaleuca north of Lake Okeechobee.