Influence of mechanical rhizome cutting, rhizome drying and burial at different developmental stages on the regrowth of Calystegia sepium

Summary The regrowth of Calystegia sepium was studied in three types of experiments during spring 2003 and spring 2004. In one glasshouse experiment, rhizome fragments were planted in pots and either harvested at six different developmental stages to assess their undisturbed development and growth or harvested at 420 day degrees after burial to measure their regenerative capacity. Regrowth gradually declined as the plants had more expanded leaves at the time of burial. Minimum regenerative capacity was found when plants had four to eight fully expanded leaves and this coincided with the growth stage of minimum dry weight of underground regenerative organs. The effects of burial depth and rhizome fragment length were studied in outdoor container experiments. Burial at 15 or 25 cm reduced above‐ and below‐ground biomass in 2004, while 25 cm deep burial was necessary to reduce regrowth in 2003. Fragmentation had generally little effect on production of above‐ and below‐ground biomass, whereas burial and fragmentation delayed emergence time. Sensitivity of rhizomes to drying was studied in a growth chamber. Drying periods of 12 or 24 h did not have an influence on the production of aerial shoots, whereas 48 or 96 h reduced production of above‐ground biomass significantly. The experiments indicated that the minimum regenerative capacity would be at about 5–6 leaf stage and that mechanical disturbance at this stage would optimise weed control.