Roundup Pro® Over the Top of Nursery Crops: Rates and Timing

Nine species of container-grown plants were treated over-the-top with Roundup Pro® (41% glyshosate) at four rates: 0.28, 0.56, 1.12, and 2.24 kg ai·ha−1 (0.25, 0.5, 1.0 and 2.0 lb ai·A−1) either in June 2007, September 2007, or February 2008. A fourth group was treated on all three dates (June + September + February) (JSF). The experiment was repeated on eight species in 2008–2009. Growth indices (GI) were taken before the spring growth flush in March and after the first growth flush in June. In Exp. 1, dwarf mondo grass (Ophiopogon japonicus ‘Nana’), mondo grass (O. japonicus), liriope (Liriope muscari ‘Cleopatra’), variegated liriope (L. muscari ‘Variegata’), and ‘Blue Pacific’ juniper (Juniperus rigida subsp. conferta ‘Blue Pacific’) were not affected by glyphosate rates up to 1.12 kg ai·ha−1 (1.0 lb ai·A−1) applied singly or JSF, except for temporary injury on ‘Blue Pacific’ from February applications. The remainder of the species had reduced growth as Roundup Pro® rates increased. ‘Blue Rug’ juniper ...