GROWTH AND LANDSCAPE ESTABLISHMENT OF PYRACANTHA AND JUNIPERUS AFTER APPLICATION OF PACLOBUTRAZOL

The long-term effects of paclobutrazol applied to container-grown 'Moj ave' pyracantha (Pyracantha x) and 'San Jose' juniper (Juniperus chine nsis L.) were investigated. Paclobutrazol was applied as a drench to c ontainer-grown (2.8 liter) plants at the rates of 0, 5, 10, 20, and 40 mg a.i./pot in June 1991, and plants were transplanted to the field i n Feb. 1992. Pyracantha plant height, shoot and root dry weight, and t otal biomass (shoot dry weight + root dry weight) decreased quadratica lly as rate of paclobutrazol increased during nursery production. Pacl obutrazol had no effect on plant height or shoot dry weight of Juniper us, although width indices were reduced. Ratings for root quality for Juniperus in containers increased as rate of paclobutrazol increased. After 9 months in the landscape, paclobutrazol still influenced plant height, width, and shoot dry weight for Pyracantha but had no effect o n Juniperus. As rate of application increased, fruit retention on Pyra cantha increased. Paclobutrazol applied as a container medium drench a t 5 mg a.i./ pot was excessive during nursery production of Pymcantha and Juniperus. Chemical name used: [(2RS, nyl)-4,4-dimethyl-2-(1,2,4-t riazol-yl)penten-3-ol] (paclobutrazol).