The effects of 10 years' intensive care on the growth of eighteen 12-year-old Pinus elliottii clones in a study area of NE Florida were compared. The clonal stock was air-layered from 11-year-old ortets of known origin. Treatments compared were : irrigation vs. no irrigation; fertilizing with uramite, superphosphate and NH4NO3 vs. no fertilizer; and disking to a depth of 5 in vs. a cover crop of Indigofera hirsuta mown annually. There were statistically significant differences in volume increment arising from both clonal and treatment effects, but the clonal influence was by far the greater. Mean total volume increment of all the clones was 9.2 ft3/tree; the most vigorous clone averaged 12.8 ft3/tree, and the least vigorous, 4.1 ft3. The ortet/ramet correlation for merchantable volume was relatively strong. Intensive culture increased increment by 4-18%. Air-layered propagules grew at the same rate as 212 commercial seedlings separating the treatment plots.