Comparing Physical, Chemical, and Cold Stratification Methods for Alleviating Dormancy of Giant Ragweed (Ambrosia trifida) Seeds

Abstract

Giant ragweed has become an increasingly important weed of arable land in many parts of North America. It is now a common weed of row crop production systems, a fact that can be attributed to earlier crop planting dates, reduced tillage, and the development of resistance to Group 2 and 9 herbicides. The propagation of giant ragweed seedlings for experimental purposes is a lengthy process because up to 90 d of stratification is often required to alleviate primary seed dormancy. The objective of this research was to evaluate physical, chemical, and cold stratification methods for alleviating seed dormancy in giant ragweed and reducing the length of cold stratification required. Results indicate that the most effective method for alleviating dormancy in seed of giant ragweed is to excise the embryo from its covering structures. By excising the embryo, 96% of viable giant ragweed seeds germinated with no stratification. In contrast, untreated seeds required a minimum of 6 wk of stratification to alleviate dormancy in a similar proportion of the population. Although excising embryos requires time and effort, the time savings relative to stratification make it an attractive method for propagating giant ragweed seedlings.