Two differential forms of growth equations, called the power decline,
or PD form, and the exponential decline, or ED form, generate classic
growth equations (such as the logistic, Chapman-Richards, Korf) and ma
ny other integral forms. Having a full range of these integral solutio
ns allows us to classify them, establish requirements to their paramet
ers, and relate these parameters and initial values (starting age and
tree size). Comparisons with data confirm theoretical results. Some ap
plications of the results are discussed.