Vol. 51—1997 - NorthEastern Weed Science Society

96
INHIBI ING THE DEVELOPMENT OF CIRCLING ROOTS IN CONTAINER GROWN
ORNAMENTALS WITH ORYZALIN
Larry J. Kuhns and Tracey L. Harpster!
INTRODUCTION
of the factors that limits the length of time a plant can remain in a container, and also
vival and growth following outplanting, is the development of a mat of circling roots
around the all of the container. Spin Out 2 is a commercially available product that has been
proven eff tive in limiting their development on many species of ornamentals. The active
ingredient n Spin Out is copper hydroxide, which is carried in a latex paint base. Spin Out is
painted on he walls of the containers. When root tips contact the copper they are killed. The
injury is I lized, though, and simply results in a more branched root system with little or no
effect on t p growth. A concern with Spin Out is the potential for accumulation of high levels of
copper ov time in areas in which the containers are painted or in the soil beneath the growing
areas.
Orjzalin is a potent root inhibitor that in certain situations has stopped root growth without
adversely fecting top growth. For example, roots growing out of the bottoms of containers set
on oryzali treated soil have been stopped without causing injury to the plants. Since oryzalin is
decompos by microorganisms in the soil, its use would have an environmental advantage over
the use of pin Out.
objectives of this study were to determine the effectiveness of oryzalin in inhibiting the
t of circling roots and its effect on plant growth.
MEfHODS
July 28, 1995 the insides of 2.5 gallon nursery containers were painted with one of the
reatments: Spin Out; latex paint' ; or Surflan 4AS4 at 0.1,0.25,0.5,2.0, or 4.0% v/v
in the late paint. On July 1 pyracantha (PyracanthacoccineaM.J. Roem.) growing in one quart
containers ere planted in the treated pots in a bark/peat medium. There were 12 pots of each
treatment d they were maintained in a completely randomized design. Plants were fertilized and
watered to maintain optimum growth. On September 12 and November 14, 1995 the plants were
rated for c rcling roots on a scale of 1 to 10, with 1 = no circling roots and 10 = many circling
roots. PIa ts were harvested and weighed on November 15.
T pots were held over the winter, and on May 2, 1996, perennial ryegrass (Latium
perenne L cv. APM) was seeded into the containers. On July 12 the circling roots were rated and
the grass d medium was discarded.
July 28 the containers were refilled and ajuga (AjugareplansL. cv. 'Burgundy Glow')
in them. Circling roots were rated on October 24, 1996.
o April 26, 1996 the insides of two gallon nursery containers were painted with one of
the follow ng treatments: 1 application of Spin Out (IX); 2 applications of Spin Out (2X); Surflan
at 0.5, 1.0 or 2.0% v/v in latex paint; Spin Out (IX) + 1% Surflan; Spin Out (IX) + 2% Surflan;
1 Prof. of mamental Horticulture and Research Associate,Dept. of Horticulture, The Pennsylvania State
University, Diversity Park, PA 16802
2 Spin Out, Griffin Corp., Valdosta, GA 31603-1847
3 Dutch B y Extra Acrylic Latex Semi-GlossEnamel (Black 19-90),Cleveland, OH 44115
4 DowEl co, Indianapolis, IN 46268-1054