In the experiments reported here, the effect of mechanical stimulation was tested on the garden rose 'Radrazz' (marketed as Knock-Out(R)), propagated by single internode cuttings. After rooting, the young plants were placed in pots (10.5cm diameter) of a peat/perlite substrate and grown in a glasshouse.
Mechanical stimulation was provided by passing a PVC tube back and forth over the cuttings so that its underside struck the stems about 3-5cm below the growing points. The bar travelled at 11 metres per hour and its height was adjusted weekly.
The frequency of movement in one experiment was once a day from Monday to Wednesday for a total of 21 back-and-forth movements. In a second experiment, it was five times a day from Monday to Thursday for a total of 95 back-and-forth movements.
The plants that were mechanically stimulated were more compact and more branched than the controls. The rose is evidently sensitive to just one dose of mechanical stimulation per day but the effect on height and branching was generally greater the more stimulation that was given.
Dr Ken Cockshull, Associate Fellow, Warwick Crop Centre, University of Warwick
Effect of Mechanical Stimulation on the Growth and Branching of Garden Rose by Morel, Crespel, Galopin and Moulia (2012).
Scientia Horticulturae 135: 59-64. The contents of issues of Scientia Horticulturae and abstracts of papers are provided at www.elsevier.com/locate/scihorti.