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Concentrations of norditerpenoid alkaloids vary among larkspur (Delphinium) species, locations, and years, but environmental stresses seem to have little effect on alkaloid levels. There is a need for a functional hypothesis of alkaloid synthesis and metabolism to explain the observed trends in concentration and to predict the toxicity of larkspur populations. This study was replicated at two locations over two years in the mountains of central Utah. Ten tall larkspur (D. barbeyi) plants were marked at each location, and a single stalk was harvested from each plant at weekly intervals throughout the growing season. Concentrations of toxic and total alkaloids were measured by Fourier-transformed infrared spectroscopy (FTIR), and alkaloid pools were calculated by multiplying the alkaloid concentration by the dry weight of the plant to determine the amount of alkaloids in the stalk. Alkaloid pools in the stalks increased for the first three weeks, leveled off, and then declined to low levels as the plants began to senesce. Concentrations of alkaloids declined through the season, as the alkaloids were diluted in the increasing biomass as the plants grew. These patterns will be used to predict potential toxicity of larkspur populations.