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Abstract

Methyl sulfanilylcarbamate (asulam) was effective for the selective control of several grassy weeds in established st. augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze), ‘Tifway’ bermudagrass (Cynodon dactylon L.), and ‘Emerald’ zoysiagrass (Zoysia matrella Merr.). Bahiagrass (Paspalum notatum Flugge) and centipedegrass (Eremochloa ophuroides (Munro) Hack.) were severely injured when asulam was used at a rate of 2.24 kg ai/ha. Thirty-six species of ornamental plants were relatively tolerant to foliage applications of asulam at rates of 2.24 and 4.48 kg ai/ha with growth normal on all but 4 ornamental species 22 weeks following treatment.

Open Access

Ornamental flowering cherry trees are popular plants for street, commercial, and residential landscapes. Grown primarily for their spring bloom, flowering cherries have been in the United States since the mid-1850s ( Faust and Suranyi, 1997 ), and

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Anthurium has emerged as a popular tropical ornamental in international markets. The cut flower consists of a brilliantly colored modified leaf called the spathe with a protruding, cylindrical inflorescence called the spadix. Spathe color is one of

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1 Current address: Department of Horticulture, Michigan State University, East Lansing, MI 48825-1325. 2 Current address: Department of Floriculture and Ornamental Horticulture, Cornell University, Ithaca, NY 14853. Support for this research was

Free access

“lesion” is used when referring to these abnormal growths. The objective of this research was to further characterize lesion nomenclature and development on four plant species: ornamental sweetpotato ‘Blackie’, tomato ‘Maxifort’, interspecific hybrid

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is that it would allow the cultivation of these healthy fruit in the major subtropical citrus belt and/or the production of ornamental citrus plants, depending on the cultivar. The second benefit is that novel fruit, leaf, and flower colors could be

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Abstract

Water soluble rooting substances were obtained from selected woody ornamentals by the centrifugal diffusion method from the cuttings, or by the water extraction method from the ground freeze-dried cuttings. Species used were Cotoneaster racemiflora soongorica, Euonymus fortunei carrierei, Ilex opaca, Lonicera maacki, Physocarpus amurensis, Symplocos paniculata, Taxus cuspidata, Viburnum burkwoodi, and V. opulus. The centrifugal diffusates from Cotoneaster racemiflora soongorica, Euonymus fortunei carrierei, and Symplocos paniculata promoted rooting of mung bean cuttings. Generally the centrifugal diffusates from all of the species studied contained 4 root-promoting fractions with Rf’s, in isopropanol:ammonia:water, of 0–0.1, 0.2–0.4, 0.6–0.8, and 0.8–1.0. All of these fractions promoted rooting of mung bean cuttings without added indole-3-acetic acid. The fraction at Rf 0-0.1 caused the strongest root promotion. Similar results were found in the water extract from the freeze-dried materials. The results strongly suggest that diffusible and water-soluble rooting substances commonly exist among many species of woody plants.

Open Access

Understanding physiological drought resistance mechanisms in ornamentals may help growers and landscapers minimize plant water stress after wholesale production. We characterized the drought resistance of four potted, native, ornamental perennials: purple coneflower [Echinacea purpurea (L.) Moench], orange coneflower [Rudbeckia fulgida var. Sullivantii (Beadle & Boynt.) Cronq.], beebalm (Monarda didyma L.), and swamp sunflower (Helianthus angustifolius L.). We measured a) stomatal conductance of leaves of drying plants, b) lethal water potential and relative water content, and c) leaf osmotic adjustment during the lethal drying period. Maintenance of stomatal opening as leaves dry, low lethal water status values, and ability to osmotically adjust indicate relative drought tolerance, with the reverse indicating drought avoidance. Echinacea purpurea had low leaf water potential (ψL) and relative water content (RWC) at stomatal closure and low lethal ψL and RWC, results indicating high dehydration tolerance, relative to the other three species. Rudbeckia fulgida var. Sullivantii had a similar low ψL at stomatal closure and low lethal ψL and displayed relatively large osmotic adjustment. Monarda didyma had the highest ψL and RWC at stomatal closure and an intermediate lethal ψL, yet displayed a relatively large osmotic adjustment. Helianthus angustifolius became desiccated more rapidly than the other species, despite having a high ψL at stomatal closure; it had a high lethal ψL and displayed very little osmotic adjustment, results indicating relatively low dehydration tolerance. Despite differences in stomatal sensitivity, dehydration tolerance, and osmotic adjustment, all four perennials fall predominantly in the drought-avoidance category, relative to the dehydration tolerance previously reported for a wide range of plant species.

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Twelve species of woody ornamentals were grown in containers in Riverside and Davis, Calif., to determine plant water use and compare crop coefficients (Kc) calculated with reference evapotranspiration (ET) from local weather stations (ETcim) or atmometers (ETatm). Water use, Kcatm, and Kccim differed by species, location, and month of the year. Raphiolepis indica (L.) Lindl., Pittosporum tobira (Thunb.) Ait., Juniperus sabina L., and Photinia ×fraseri Dress. were the highest water users in Riverside and Arctostaphylos densiflora M.S. Bak., Juniperus, Cercis occidentalis Torr., and Pittosporum used the highest amount of water in Davis, when averaged over the 20-month study period. Rhamnus californica Eschsch., Prunus ilicifolia (Nutt.) Walp., and Cercocarpus minutiflorus Abrams. were among the lowest water users in both locations. Although plant water use fluctuated considerably between individual sampling dates, the relative ranking of species water use in each location changed very little over the study period. During periods of high winds, ETcim may not provide an accurate reference for container crops. Kc values fluctuated seasonally from as much as 1 to 4.7 for high water users, while values were stable for low water users and also for Buxus microphylla japonica Rehd. & E.H. Wils., an intermediate water user. During periods of low ET, especially in fall and winter, Kc values were artificially high and failed to correspond to the plants' low water use. Kc values for low water users seem to be useful to estimate water requirements over an extended period of time, whereas general Kc values seem to have limited value for plants with high water demand and need to be modified for different growth stages and growing locations.

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Abstract

Stems of many woody ornamental plant taxa were collected in midwinter and hardened to their maximum capability under laboratory conditions. Hardiness levels were determined and compared to zone recommendations as listed in Hortus III and Rehder’s Manual of Cultivated Plants. Many woody plants had a greater midwinter cold tolerance than their hardiness ratings would infer.

Open Access