AbstractAlthough seed dormancy is advantageous for annual plants in the wild, unsynchronized germination in the laboratory leads to increased error in measurements. Therefore, techniques to promote and synchronize germination are routinely used. Ultrasound is one of the newest methods for breaking dormancy in weed seeds. We have investigated whether ultrasonic waves can be used to break seed dormancy of common lambsquarters (Chenopodium album), a highly competitive annual weed that leads to significant reduction of yields of corn, soybeans, and sugar beets. Ultrasonic waves with frequency of 35 kH were applied for 0 (control), 5, 10, 15, and 30 min using a completely randomized design. The results showed that the use of ultrasound waves generally enhanced the traits under investigation in the treated samples compared with the control sample. The maximum enhancement of germination percentage (180%), seedling dry weight (78%), and seedling vigor index I (271%) and II (392%) was seen in the common lambsquarters samples treated with ultrasound for 15 min and seedling length (40%) at 30 min compared with the control samples. Radical lengths were not statistically different from controls under any treatment and plumule length only increased marginally. These changes are reflected in seedling vigor index I and II measurements. For some of these traits, increasing the length of ultrasound treatment to 30 min had negative effects. These results demonstrate that ultrasound technology can be used as a quick, and efficient nondestructive method to break seed dormancy in common lambsquarters.