Rhizomes were sampled from quackgrass sod weekly during two seasons. The activity of buds on one-bud sections from mature rhizomes was used to determine periods of growth and dormancy. The rhizome buds showed a steady decrease in activity from mid-April to June 1. During June, the buds were dormant. Recovery began in late June and continued the rest of the summer. Only one-third of all rhizome material in a three-year-old sod was viable. The amount of viable mature rhizomes decreased during the season while the viable new rhizomes increased, and the total viable level remained fairly constant. This suggested a definite cycle in rhizome production and decomposition from year to year and a short life-period in the soil. The term “late-spring dormancy” is suggested for quackgrass rhizomes, based on the prevailing cool and moist weather conditions and the late-spring time of occurrence during the year. This distinguishes the type of dormancy described from “summer dormancy”.