Field and laboratory germination responses of achenes of Polygonum lapathifolium, P. pensylvanicum, and P. persicaria

Abstract

The annual smartweeds Polygonum lapathifolium L., P. pensylvanicum L., and P. persicaria L. are weeds of cereal crops, waste places, and wet ground in Canada. Their ‘weediness’ is attributed, in part, to the production of large numbers of achenes which are capable of lying dormant in the soil for several years or until suitable conditions arise for germination.Dormancy–germination characteristics of achenes from Ontario plants were examined in the laboratory and in the field. Three types of dormancy have been identified, each of which prevents germination under a different set of unfavourable conditions. An innate dormancy prevents germination in fresh achenes immediately prior to winter. An enforced dormancy prevents germination during the winter and in achenes which are deep in the soil. An induced dormancy is caused by hot or dry periods (at least in P. persicaria). Germination occurs as a series of flushes whenever achenes are brought to the soil surface and (or) whenever rainy spells occur.