Rumex crispus and Rumex obtusifolius regeneration from root fragments is affected by fragment weight, root section and depth of planting

Abstract

Rumex crispus (curled dock) and Rumex obtusifolius (broad leaved dock) are among the most problematic temperate zone perennial weeds of arable crops, abundant in a wide variety of conditions. Their root fragments, created during routine agricultural practices, are known to regenerate. Regeneration from two fragment weights and from different parts of the upper root and taproot was measured and compared between the species, in a winter field trial. A second field trial, which spanned winter into the following late spring, considered the effects of increasing the planting depths of root fragments. Biometric measures in both trials were above ground dry weight, leaf area, the number of shoots produced and below ground root fresh weight. From the first trial, total emergence was low in both species (31% in R. crispus and 37.5% in R. obtusifolius), tailed off quickly and only occurred from the upper or mid-root sections, with significant differences in emergence between species and the root fragment section, but not fragment starting sizes. The likelihood of plants emerging was significantly higher in R. obtusifolius and from the top root fragment section, growth from the root mid-section only occurred in R. obtusifolius. Root fragment starting weight made no significant difference. Rumex obtusifolius produced significantly less above ground dry weight, leaf area and shoots than R. crispus. More shoots were produced from larger root fragments in both species. In the winter to early summer trial both species showed weak early regeneration, which quickly tailed off, with R. crispus emerging in significantly greater numbers than R. obtusifolius. Notably, emergence resumed strongly the following spring-early summer in both species. Increasing soil depth was related to a significant decrease in emergence and impacted on all biometrics similarly, except fresh root weight which increased at moderate planting depths before tailing off. These findings confirm the potential for vegetative regeneration of both species, contribute to our understanding of factors influencing their regrowth and highlight key differences between them which can be used to improve control practices.