Abstract: A series of ester and salt derivatives of fluorene-9-carboxylic acid and fluorene-1-carboxylic acid exhibit significant plant growth regulating properties, useful in controlling the size, shape, dormancy time, flowering time and/or fruit setting of plants, depending upon the concentrations used. They may also be used to control the growth rate, texture and color of turf grass. Presently preferred compounds include the cis-2,5-dimethylpyrrolidine salt of 1-fluorenecarboxylic acid, 9-cis-2,5-dimethyl-1-pyrrolidinyl-2-chlorofluorene-9-carboxylic acid, methyl ester, the 2,6-dimethylpiperidine salt of 1-fluorenecarboxylic acid, and the cis-2,5-dimethylpyrrolidine salt of 9-hydroxyfluorene-9-carboxylic acid.