December 1, 1996
'Hamlin' trees on several rootstocks of different vigor were randomly planted in 1986 throughout part of a 30-yearold grove in central Florida to study the effects of tree vigor and the competitive environment on tree behavior. The 30- year-old trees were on rough lemon (C. jambhiri Lush.) rootstock in N-S rows. The experiment trees were used for interplanting and resetting. The in-row spacings between the experiment trees and the adjacent ones varied from 7 ft to 15 ft. All trees were irrigated with microsprinklers; cultural practices were typical for the Astatula fine sand soil at the site. Heights of the test trees were measured periodically, and yield was rated annually between 1991 and 1996. These data were used at the end of the study to compare each experiment tree to a ranking of its competitive environment based on the size and proximity of the two possible adjacent trees. Heights of the 10-year-old test trees on the citrange or mandarin rootstocks were about 11 ft to 13 ft, and were 6 ft to 8 ft for those on C-35 citrange. Tree heights generally decreased 30%, and yield 50%, as tree-to-tree competition increased. These responses were independent of tree vigor for the rootstocks tested.