Cut Less-Growth Control of Five Landscape Shrubs By Flurprimidol and Irrigation

Shrubs used as hedges in urban landscapes require frequent trimming to maintain desired size and shape, which has becomes a top cost contributor to landscape service companies due to labor cost for trimming and cleaning and equipment wear. Cutless.33G is a granular formulation of the plant growth regulator flurprimidol and has provided relatively longer residual effect on woody ornamentals in a previous study. The objective of the present study was to evaluate how the effects of this granular product may be affected by irrigation method. Cutless .33G at 0, 14 or 21 lbs/1000 ft² and three irrigation methods: micro-sprinkler, drip irrigation, or no-irrigation, were evaluated for their effects on the growth and quality of burford holly, elaeagnus, ligustrum, sweet viburnum, and wax myrtle from 2013 to 2015. Plant growth responses to Cutless were species specific. Wax myrtle was the most responsive with 31% size reduction at 21 lbs/1000 ft² compared with the untreated at 8 weeks after treatment. Compared with drip and no-irrigation, overhead micro-sprinkler resulted in smaller plants in elaeagnus and wax myrtle across Cutless rates. However, this effect was affected by rainfall amount and inconsistent among years. Elaeagnus and sweet viburnum had no or inconsistent response to either Cutless or irrigation. However, time spent for trimming the hedges treated with Cutless and resulting clipping amounts were significantly less than those of the untreated to maintain the same hedge height and width. Overall, irrigation is important for effective delivery of this PGR to the plant and its benefit in growth regulation was significant in reducing time spent in triming, cleaning, and potentially equpment wear.