Influence of defoliation on toxic alkaloid concentration and alkaloid pools in tall larkspur

This study was replicated at two locations in the mountains of central Utah . In 1997, ten uniform plants of tall larkspur (Delphinium barbeyi) in the early bud stage (40 cm in height) were selected at each site and clipped at 5 cm above soil level. In 1998, one stalk from each plant wan harvested on a weekly basis: in 1999, one stalk was harvested at four times during its phenological development. Toxic and total alkaloid concentrations were meas ured and alkaloid pools in the entire stalk were calculated. Clipping reduc ed stalk height to less than 50 cm in 1998 and 65 cm in 1999, compared to o ver 100 cm in unclipped control plants. Alkaloid concentration was similar to control plants, bur toxic alkaloid pools were 70% lower than control pla nts. because of the reduction in biomass of the stalks. Clipping reduced su bsequent vigor and the amount of toxic and total alkaloids in tall larkspur .