Intense fragmentation and deep burial reduce emergence of Rumex crispus L.

Mechanical control through different tillage methods is a common measure against perennial weeds. However, non-optimal tillage can potentially increase the vegetative regeneration instead of reducing it. Aspects of regenerative capacity in the perennial weed species Rumex crispus L. was studied in three pot and box experiments as follows: (1) regeneration from different root fragments under varying test conditions; (2) effects of root size and burial depth on time of emergence and emergence rate; and (3) effects of burial depth and cutting on biomass production and seed production. In experiment 1, sprouting occurred mainly from the neck of the roots, consisting of underground stem tissue. A few shoots were observed also from the upper half of the true taproot and from a side root. No difference in sprouting was found between test conditions. In experiment 2, total emergence rate was positively related to root size and negatively related to burial depth. Time to first emergence was defined by an interaction between the two factors. Roots larger than 100 g gave rise to a high degree of emergence from all burial depths, while emergence from roots weighing 20-30 g was less than 30% from 12 cm and nonexistent from 18 cm. When emergence and shoot production were tested under different cutting regimes (experiment 3), the separated top fragments of the roots sprouted faster and produced more shoot biomass than intact rootstocks, even at a second harvest. Our results indicate that fragmentation can stimulate sprouting from the regenerative tissue of the taproot. Hence, if tillage is carried out as weed control it is important that root fragments are buried at ploughing depth, especially if the population consists of adult plants.