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The objective of this study was to evaluate the effect of weed placement on the growth of container-grown ornamental plants. Additionally, it also assessed the safety of applying herbicides beneath and on the slits of air-pruning containers using four common container-grown ornamental plants. The study was divided into three experiments, with uniform liners of pentas (Pentas lanceolata (Forssk.) Deflers) and golden dewdrop (Duranta erecta L.) in the first experiment and pentas in the second. The weed seedlings, consisting of either ageratum (Ageratum houstonianum Mill.) or eclipta (Eclipta prostrata L.), were positioned in one of three locations within the container, either directly beside the rootball of the ornamental plant, 2.5 cm away from the rootball, or inside the drain hole of the container. The third experiment involved four ornamental species, which were utilized to assess the safety of herbicide application either beneath or on the slits of air-pruning containers. The overall results of the first two experiments revealed that weeds growing either at the center or the sides of the ornamental plant rootball had significant competitive effects on the growth of the ornamental species. In case of the third experiment, no herbicide injury was observed on the ornamental species, with a minor decrease in the growth of loropetulam (Loropetalum chinensis ‘Ruby’).

The objective of this study was to determine how topdressing or incorporating fertilizer with stratified or mulched substrates could affect the growth of Hibiscus rosa-sinensis ‘Snow Queen’, a popular ornamental plant, and the growth of liverwort (Marchantia polymorpha) and bittercress (Cardamine flexuosa), two common nursery weed species. Five different substrate treatments were evaluated, which included three stratified substrates composed of pine bark screened to a small (0.63–1.27 cm), medium (≤1.90 cm), and large (0.96–1.90 cm) particle size and two industry-standard substrates that were either mulched with rice hulls or remained unmulched. All treatments were then fertilized via either topdressing or incorporating a controlled-release fertilizer (CRF). Bittercress control was highest in mulched containers, followed by those stratified using the medium pine bark, and its growth increased overall in topdressed vs. incorporated containers regardless of substrate or mulch treatment. All the stratification treatments resulted in a decrease in liverwort coverage compared to the industry standard treatment, but topdressing generally increased liverwort coverage compared with incorporating fertilizer. In conclusion, both topdressing and incorporation appear to be compatible with fertilizer placement methods with substrate stratification from a crop production standpoint; however, weed growth may increase if fertilizer is topdressed.

The objective of this study was to assess the growth of two woody ornamental plants when subjected to different levels of weed competition in four different container sizes, representing different stages of production. Ligustrum (Ligustrum lucidum W.T.Aiton) and Japanese holly (Ilex crenata Thunb.) liners were potted individually into 3.8 L, 11.4 L, 24.7 L, and 56.8 L containers, respectively. Weed coverage of 0%, 50%, and 100% in each container size was maintained by surface sowing seeds of six common nursery weed species by volume, based on media surface area in each pot. Results showed that the shoot dry weight of ligustrum at 50% and 100% weed levels was reduced by 28% and 35%, 55% and 56%, 41% and 43%, and 12% and 14% in 3.8 L, 11.4 L, 24.7 L, and 56.8 L containers, respectively. The shoot dry weight of Japanese holly at 50% and 100% weed levels was reduced by 18% and 22%, 51% and 52%, 51% and 53%, and 40% and 53% in 3.8 L, 11.4 L, 24.7 L, and 56.8 L containers, respectively. Results indicate that weed competition at 50% and 100% weed level was similar across all four container sizes, and weeds remained competitive even in the larger container sizes.