Project Number: 3607-21000-011-03
Project Type: Specific Cooperative Agreement

Start Date: Sep 25, 2003
End Date: Aug 30, 2008

Objective:
This research proposal has three objectives: 1) to determine young and mature root hardiness values for containerized plants not treated with herbicides; 2) to determine young and mature root hardiness values for containerized plants that receive DNA herbicide treatments prior to overwintering; and, 3) to investigate differences in growth potential between untreated and DNA herbicide treated containers two and six months after emergence from overwintering.

Approach:
The nursery industry is continually increasing the production of woody ornamental landscape shrubs in ambient temperature as a limiting factor. Containers offer no insulation for roots from the cold. A plant is only as hardy as its roots. One of the common practices in overwintering is the application of preemergent dinitroanaline (DNA) herbicides prior to covering container stock. DNA herbicides work by root inhibition but injury to roots may occur. Cornus, Berberis, Spirea and Viburnum will be sprayed during the growing season with Surflan (Oryzalin), Barricade (Prodiamine), Pendulum (Pendimethalin), or Treflan (Trifluralin). Cold hardiness and delayed and/or retarded growth or injury will be evaluated at two sampling dates during the overwintering period. All plants will be evaluated using growth index and dry weight measures of roots the following spring. Treatment effects will be compared by analysis of variance and least significance difference test was used to compare means with suitable graphic.