LONG-TERM SURVIVAL OF GOLDEN TRUMPET TREE AND COPPERPOD ON ROCKLAND SOIL IN SOUTH FLORIDA

Abstract

The soil in south Miami–Dade Co., Fla., consists of 4 to 6 inches of scarified limestone, officially a “very gravelly loam”. The bedrock reaches the surface; with little weathered material or organic matter. Heavy equipment is used to break up the rock, and a rock plow is used every few years to prevent re-compaction. Street trees in swales are installed in shallow holes dug in the rock and back-filled with crushed limestone. Golden trumpet tree, or yellow tab, Tabebuia chrysotricha, and copperpod, Peltophorum pterocarpum, are deciduous, tropical trees of medium size. Both are popular throughout south Florida because they produce spectacular displays of yellow flowers before the leaves emerge in the spring. When planted on rockland soil, both species present maintenance problems which suggest that they may not be good choices for use as street trees. In Summer 2005, after three hurricanes, both species were evaluated for long-term survival. Of 246 Tabebuia, 26% fell, 18% leaned (or 45% damaged), and 25% were missing, having been destroyed in previous years. Only one was broken, the rest fell due to root failure. Six large trees growing near buildings were standing. It appears that yellow tab is not a good street tree in rockland, not even for the short-term. Of 142 Peltophorum, 23% fell, 3% leaned (or 26% damaged), and 4% were missing. Due to an umbrella-like branching pattern, 15% had branches broken on the street side, caused by vehicles, not wind. Though it sustained only half the wind damage of yellow tab, copperpod is not a good street tree, due to poor branching patterns.