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Ornamental groundcovers are a popular alternative to turfgrass in landscapes due to their low maintenance requirements, pest resistance, and shade tolerance. Weed control is a challenge in these groundcovers because few herbicide options are available. The objective of this research was to determine the tolerance of the groundcovers Asiatic jasmine [Trachelospermum asiaticum (Nakai) ‘Minima'], perennial peanut [Arachis pintoi (Krapov.& W.C. Greg.) ‘Golden Glory'] and dwarf mondo grass [Ophiopogon japonicus (L.f.) Ker Gawl.] ‘Nana'] to herbicides, including bentazon, clopyralid, fluazifop-P-butyl, glufosinate, halosulfuron, imazaquin, sethoxydim, sulfentrazone, and sulfosulfuron applied at approximately 2 times the label rate. Asiatic jasmine and perennial peanut were evaluated in Apopka, FL and dwarf mondo grass was evaluated in Mobile, AL. Bentazon, clopyralid, glufosinate, glyphosate, and sulfosulfuron caused unacceptable injury and/or a reduction in shoot growth for all three species while fluazifop-P-butyl and sethoxydim caused no injury to any species. Halosulfuron caused minor injury but significantly reduced growth of dwarf mondo grass. Sulfentrazone caused no injury to Asiatic jasmine or perennial peanut but caused severe injury to dwarf mondo grass after only one application. Similarly, imazaquin caused only minor injury to Asiatic jasmine and dwarf mondo grass but significantly reduced growth of perennial peanut after two applications.Index words: Postemergence herbicides, groundcovers, mondo grass, perennial peanut, Asiatic jasmine.Chemicals used in this study: Bentazon (Basagran® T/O), 3-(1-methylethyl)-1H-2, 1,3-benzothiadiazin-4(3H)-one 2,2-dioxide, clopyralid (Lontrel), 3,6-dichloro-2pyridinecarboxylic acid, fluazifop-P-butyl (Fusilade® II), (2R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid, Glufosinate (Finale®), 2-amino-4-(hydroxymethylphosphinyl)butanoic acid, Glyphosate (Ranger® PRO), N-phosphonomethyl)glycine, Halosulfuron-methyl (SedgeHammer®), methyl 3-chloro-5-[[[[4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]-1-methyl-1H-pyrazole-4-carboxylate, Imazaquin (Sceptor® T&O), 2-[4,5-dihydro-4-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid, Sethoxydim (Sethoxydim SPC), 2-[1-ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one, Sulfentrazone (Dismiss®), N-[2,4-dichloro-5-[4-difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl]phenyl]methanesulfonamide, Sulfosulfuron (Certainty®), 1-(4,6-dimethoxypyrimidin-2-yl)-3-[(2-ethanesulfonyl-imidazo[1,2-a]pyridine-3-yl]sulfonylurea.Species used in this study: Asiatic jasmine ‘Minima' (Trachelospermum asiaticum ‘Minima'), perennial peanut (Arachis pintoi ‘Golden Glory'), dwarf mondo grass (Ophiopogon japonicus ‘Nana').

Research objectives were to determine the effect of fertilization method (incorporation, subdress, and topdress) on weed growth and the performance of preemergence herbicides applied to soilless substrates. Nursery containers were filled with a pine bark:peat substrate and fertilized at two different rates [4.4 and 9.5 kg.m−3 (8.9 and 19.2 lb.yd−3)] via topdressing, subdressing, or incorporating. Containers were treated with either dimethenamid-P for spotted spurge (Euphorbia maculata L.), flumioxazin for eclipta (Eclipta prostrata L.) or prodiamine for large crabgrass (Digitaria sanguinalis L.). A control was established for each fertilizer rate/placement and weed species that was not treated. Incorporating or subdressing fertilizer resulted in reduced large crabgrass and spotted spurge growth in non-treated containers. Weeds grew larger at the higher fertility rates in both topdress and incorporated treatments but fertilizer rate did not affect growth of spotted spurge or large crabgrass when fertilizers were subdressed. Herbicides generally provided commercially acceptable weed control regardless of fertilizer treatment, but results varied with species. Results suggest that in the absence of herbicides, topdressing may result in greater weed growth compared with subdressing or incorporating fertilizers; however, fertilizer placement will have less impact on herbicide performance if proper herbicides are chosen and applied correctly.Index words: topdress, subdress, incorporate, large crabgrass, eclipta, spotted spurge, preemergenceChemicals used in this study: Flumioxazin (SureGuard®); 2-[7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazin-6-yl]-4,5,6,7-tetrahydro-1H-isoindole1,3(2H)-dione; Dimethenamid-P (Tower) 2-chloro-N-[(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)acetamide; Prodiamine (Barricade) 2,4-dinitro-N3, N3-dipropyl-6-(trifluoromethyl)-1,3-benzenediamine (Barricade®)Species used in this study: Large crabgrass (Digitaria sanguinalis L.); Eclipta (Eclipta prostrata L.); Spotted spurge (Euphorbia maculata L.)

The objective of this research was to evaluate dithiopyr and isoxaben combinations and indaziflam (Marengo) for early postemergence control of woodland bittercress (Cardamine flexuosa) and yellow woodsorrel at 4 different early growth stages. Herbicides evaluated included sprayable formulations of isoxaben, dithiopyr + isoxaben, dithiopyr, indaziflam, and prodiamine + isoxaben without any surfactants. Woodland bittercress growth stages included seed production (extra-large), recently flowered (large), 6 to 9 leaf (medium) or in 2 to 5 leaf stage (small), while yellow woodsorrel growth stages included 8 to 12 leaf stage (extra-large), 4 to 6 leaf stage (large), 2 to 4 leaf stage (medium) and cotyledon to 1 leaf stage (small). Shoot fresh weight data showed all treatments provided ≤98% of woodland bittercress at the small stage. Dithiopyr + isoxaben (98%), isoxaben (90%), and indaziflam (93%) provided the highest level of woodland bittercress control at the medium stage and were the only treatments providing acceptable control (≥80%). In the large stage, dithiopyr + isoxaben provided acceptable control (80%) and outperformed other treatments. All treatments with the exception of isoxaben generally provided acceptable control of yellow woodsorrel up to the large growth stage. Only indaziflam (86% control) provided acceptable control at the extra-large stage. Index words: herbicide, postemergence weed control, container-grown plants, phytotoxic damages. Herbicides used in this study: isoxaben (Gallery® 4SC) N-[3-(1-ethyl-1-methylpropyl)- 5-isoxazolyl]-2,6-dimethoxybenzamide; dithiopyr (Dimension® 2EW) S,S'-dimethyl 2-(difluoromethyl)-4- (2-methylpropyl)-6-(trifluoromethyl)- 3,5-pyridinedicarbothioate; indaziflam (Specticle® FLO) N-[(1R,2S)-2,3-dihydro-2,6-dimethyl-1H-inden-1-yl]-6-(1-fluoroethyl)-1,3,5-triazine-2,4-diamine; prodiamine + isoxaben (Gemini® SC) 2,4-dinitro-N3,N3-dipropyl-6-(trifluoromethyl)-1,3-benzenediamine + N-[3-(1-ethyl-1-methylpropyl)- 5-isoxazolyl]-2,6-dimethoxybenzamide; dithiopyr + isoxaben (Dimension® + Gallery®) S,S'-dimethyl 2-(difluoromethyl)-4- (2-methylpropyl)-6-(trifluoromethyl)- 3,5-pyridinedicarbothioate + N-[3-(1-ethyl-1-methylpropyl)- 5-isoxazolyl]-2,6-dimethoxybenzamide. Weed species evaluated: woodland bittercress (flexuous bittercress) (Cardamine flexuosa With.); yellow woodsorrel (Oxalis stricta L.).

Due to the relatively small market, volatility concerns, and high crop-value-per-acre associated with ornamental crops, no preemergence (PRE) herbicides are currently labeled for use in greenhouses containing plants. The objective of this study was to evaluate indaziflam SC for potential use as a PRE herbicide on gravel in greenhouses containing sensitive crops grown in extreme environmental conditions. Mini-greenhouses (MG) were designed and constructed to fit within gravel ground beds as an initial component to this study in order to evaluate herbicide volatility. Species evaluated included ‘Better Boy’ tomato (Lycopersicon esculentum Mill.), ‘Extreme Orange’ impatiens (Impatiens walleriana Hook. f.) and two species of petunia (Petunia × hybrida Juss. ‘Dreams White’ and ‘Dreams Neon Rose’). Indaziflam SC was applied at the manufacturer's labeled rate [40 g ai·ha−1 (0.04 lbs ai·A−1)] (1×) and at twice the labeled rate [80 g ai·ha−1 (0.07 lbs ai·A−1)] (2×). Each rate was applied using one of three different methods: 1) applied to only the gravel in ground beds with plants placed on gravel and covered with MG immediately following application; 2) applied over the top of plants on gravel inside the ground beds and covered with MG immediately application; and 3) applied over the top of plants outside the ground beds on adjacent gravel and left outside of MG. Two nontreated control treatments were maintained for each species and were placed either on nontreated gravel inside ground beds and covered with MG or placed outside ground beds on adjacent nontreated gravel and not covered with MG. Little to no injury was observed on any of the species after being placed on treated gravel and covered with a MG regardless of indaziflam rate. However when indaziflam was applied over-the-top, impatiens and tomatoes exhibited severe injury and death by 30 days after treatment (DAT). Additionally, fresh weights showed that all species receiving either over-the-top treatment were severely injured, while the plants placed on treated gravel inside the MG and both nontreated control treatments (both inside and outside of MG) exhibited no signs of injury or stunted growth. Results from this study indicate that while indaziflam may cause crop injury to ornamental species when applied over-the-top, it is likely that little to no injury will be observed as a result of volatility due to a gravel application in an enclosed structure.

Due to concerns over future pine bark (PB) availability for container plant production, recent research has focused on evaluating suitable alternatives. For alternatives to be considered suitable substrate replacements, they must not only have desirable characteristics as a container substrate (e.g., adequate drainage, inert, pathogen free, etc.), but must also cause no negative fertility effects (e.g., nitrogen immobilization) following planting in the landscape. The study objective was to evaluate the landscape performance of three woody ornamentals grown in PB and in two alternative wood-based substrates, namely WholeTree (WT) and Clean Chip Residual (CCR). Crapemyrtle (Lagerstroemia indica × faurei ‘Acoma’), magnolia (Magnolia grandiflora ‘D.D. Blanchard’), and shumard oak (Quercus shumardii) were container grown in PB, WT, or CCR for an entire growing season prior to being planted into the landscape. Plants were grown in the landscape for two growing seasons. Data suggest that all species exhibited similar landscape performance when grown in WT or CCR compared to the PB standard. Therefore, the use of WT and CCR as alternative wood-based substrates for crapemyrtle, magnolia, and oak production may be acceptable from a landscape establishment standpoint.

Four experiments were conducted to evaluate early postemergence control of spotted spurge (Chamaesyce maculata) in nursery crops using preemergence active herbicides. In Experiment 1, spotted spurge (SS) seed were overseeded at two different dates in a commercial pine bark substrate and were grown until reaching either the cotyledon to one leaf (C–1L) stage, or the two to four leaf (2–4L) stage. Herbicides applied included: Broadstar 1604 (flumioxazin), V-10142 (imazosulfuron), and Tower (dimethenamid-P). These products were applied postemergence at their respective recommended label rate (1 ×) and twice (2 ×) this rate to SS either at the C–1L stage or at the 2–4L stage. In general, V10142 and Tower provided the greatest injury to SS in the C–1L. Tower also provided greatest SS injury in the 2–4L stage. In Experiment 2, postemergence control was tested in the C1-L and 2–4L stages with Broadstar 1604, FreeHand (dimethenamid-P 0.75% + pendimethalin 1.0%), Tower, and Pendulum 3.3 EC (pendimethalin) at the 1× and 2× the label rate. FreeHand at 2×, along with Tower and Pendulum at both rates provided the highest SS injury ratings in the C–1L. Tower at 2× and Pendulum at both rates provided greatest SS injury in the 2–4L. In Experiments 3 and 4, Broadstar (1/2×, 1×, and 2× rate), Casoron (dichlobenil) (1× and 2×), HGH-63 (oxyflurfen) (1×), Certainty (sulfosulfuron) (1× and 2×), Tower (2/3× and 1×), V-10142 (1× and 2×), Pendulum 3.3 EC (1× and 2×), FreeHand (1× and 2×) were applied to SS in either C–1L or 2–4L as described above. Results from Experiments 3 and 4 indicate that Certainty (both rates), Tower (both rates), Pendulum (both rates), and FreeHand (both rates) have postemergence activity on immature SS, especially when applied in the C–1L stage. Postemergence activity declined when herbicides were applied to SS in the 2–4L, however Pendulum (both rates), Certainty (both rates), and FreeHand (2× rate) had a marginal effect.

Agriculture is a large contributor of trace gas emissions and much of the work on reducing greenhouse gas (GHG) emissions has focused on row crops and pastures, as well as forestry and animal production systems; however, little emphasis has been placed on specialty crop industries such as horticulture. Our objective was to determine efflux patterns of CO2, CH4, and N2O associated with four different nursery container sizes [3.0 liter (trade gal; TG), 3.8 liter (#1; 1 gal), 7.6 liter (#2; 2 gal), and 11.4 liter (#3; 3 gal) using dwarf yaupon holly (Ilex vomitoria ‘Nana’ L.) grown under common production practices for one year. Weekly measurements indicated that carbon dioxide (CO2) and nitrous oxide (N2O) fluxes were highest in the largest containers (#3). There was a significant positive relationship between container size and CO2 efflux. Nitrous oxide efflux followed a similar pattern, except there were no differences between the two smallest container sizes. In general, CO2 and N2O fluxes increased with increasing temperature. Methane flux was consistently low and had no significant effect on total trace gas emissions. Results from this study begin to address uncertainties regarding the environmental impact of the horticulture industry on climate change while providing baseline data of trace gas emissions from container production systems needed to develop future mitigation strategies.