This article presents the results of an experimental study designed to determine quantitatively the rates of heat transfer by convection from broad leaves of various plants and trees under conditions approximating those in an ecosystem in nature. Empirical relations, applicable to the different types of leaf shapes found in nature, are derived from the experimental data for free and forced convection. The influences of leaf position relative to the wind or the direction of the gravitational force field, the presence of other branches or leaves in the vicinity, and the flutter in the wind also have been investigated.