Summary Rumex species are important weeds in grasslands and on arable land. The Rumex hybrid (R. patienta × R. tianschanicus; cv. OK‐2, Uteusha) has been planted as a forage and energy crop since 2001 in the Czech Republic, but its ecological requirements and its potential to become a new weedy species have never been investigated. In 2010 and 2011, we performed a pot experiment to investigate the effect of none, one and two cuts per year on biomass production of Rumex OK‐2 and common broad‐leaved Rumex species (Rumex obtusifolius, R. crispus and R. alpinus). The higher cutting frequency can reduce the belowground biomass, but no effect on the aboveground biomass was detected. Flowering in the seeding year was recorded in only 50% of R. obtusifolius plants. Non‐flowering R. obtusifolius plants produced significantly more belowground biomass than flowering plants under no cutting or one cut treatments. The growth response of Rumex OK‐2 to different cutting treatments was very similar to R. crispus. These similarities indicate the weed potential of the hybrid to become a troublesome weedy species, similar to R. crispus.

No abstract

Dynamics of above-ground and below-ground biomass of Rumex crispus, Rumex obtusifolius and the new weedy species Rumex hybrid cv. OK-2 Summary Docks can be serious weeds of arable land and permanent grasslands where they can persist through wellestablished root systems. A Rumex hybrid (R. patientia x R. tianschanicus; cv. OK-2, Uteusha) has been planted as a forage and energy crop since 2001 in Czechia and has now become a new weed species. As its ecological characteristics are unknown, there is a need for improved knowledge for developing control measures and strategies. In 2010 and 2011, we performed a tube pot experiment to investigate above-ground and below-ground biomass growth dynamics and below-ground biomass allocation of Rumex OK-2. We compared the hybrid with Rumex crispus and Rumex obtusifolius during the vegetation season in the seeding year. Above-ground and below-ground biomass of Rumex species tended to increase from July to September. In the seeding year, flowering was recorded only for one plant of Rumex OK-2 and 27.5% of R. obtusifolius plants, whereas R. crispus did not flower. The proportion of below-ground biomass of Rumex species in the upper 30 cm was about 70-80%. The growth dynamics and allocation of below-ground biomass of Rumex OK-2 were more like R. crispus than to R. obtusifolius. These similarities indicate the potential of Rumex OK-2 to become a troublesome weedy species, comparable with R. crispus.Keywords: broad-leaved dock, curled dock, Rumex OK-2, biomass allocation, soil depth, root system. HUJEROVA R, PAVL U L, PAVL U V, HEJCMAN M & GAISLER J (2017). Dynamics of above-ground and below-ground biomass of Rumex crispus, Rumex obtusifolius and the new weedy species Rumex hybrid cv. OK-2 (R. patientia x R. tianschanicus) in the seeding year. Weed Research 57, 81-90.