The response of four quackgrass biotypes to desiccation was investigated. Rhizomes from field populations of each biotype were harvested at four predetermined dates over 1 yr. At each harvest date, rhizomes were transferred to the laboratory and subjected to four levels of desiccation. Desiccated rhizomes harvested in November and June regenerated significantly more shoots than those harvested in May and July. At 60% desiccation, regeneration ranged from 63 to 93%, depending upon the biotype. The lowest regeneration occurred with the Manitoba biotype, M7, harvested in May or July. The Quebec and Ontario biotypes had at least 87% regeneration at each harvest date. Key words:Elytrigia repens, quackgrass, biotypes, desiccation tolerance, weed control