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  • Author or Editor: R.I. Cabrera x
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Containerized crape myrtle (Lagerstroemia indica L. × Lagerstroemia fauriei Koehne `Tonto') plants were grown for 9 months under various nitrogen fertility regimes, and then transplanted to a sandy loam soil with minimal management to evaluate their landscape establishment and growth performance. During the nursery phase plants were irrigated, except over an overwintering period, with complete nutrient solutions differing in applied N concentration, ranging from 15 to 300 mg·L-1. By 16 weeks after transplanting (WAT) into the landscape soil, plant biomass was significantly higher in the plants that had been grown with higher N supplies and had been among the smallest at transplant. Such plant growth response was linearly and positively correlated to plant N status at transplant. Plant shoot to root ratio and tissue N, Ca, S, and Fe concentrations, which had been significantly affected by the N fertilization regime in the nursery, equalized over time after transplant, with no significant differences observed among treatments by 16 WAT. Flowering response in the landscape was delayed in plants originally grown with the higher N supplies. Plant survival and establishment per se were not affected by treatments; no plants were lost, and aside from the differences in size and flower timing, all plants were considered aesthetically similar.

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Greenhouse rose plants, `Bull's Eye', budded on the rootstocks Rosa manetti and R. × `Natal Briar', were grown in containers filled with a peat-based growing medium. The plants were irrigated with a 0.5× Hoagland solution salinized with a fixed 12-mM Na solution made up of seven ratios of NaCl, Na2SO4, and NaNO3 (100:0, 50:50:0, 0:100:0, 0:50:50, 0:0:100, 50:0:50, and 33:33:33). The results after four flushes of growth and flowering showed higher dry weight productivities in R. manetti plants. Salt composition (i.e., counter-anion ratios) significantly affected the dry weight yield of `Natal Briar' plants, with those irrigated with 100% Na2SO4 and NaNO3 having the highest and lowest values, respectively. While the plants budded on R. manetti did not show significant responses to salt composition, there was a strong tendency for higher dry weight yields in binary salt (anion) compositions. Leachates collected throughout the study showed similar pH (7.5) and electrical conductivities (4.7 dS/m) for all salt treatments. Leachate Cl- concentrations were linearly correlated with Cl- application, whereas leachate Na+ concentrations remained similar among treatments. Plants on R. manetti accumulated less leaf Na+ and Cl- than in R. × `Natal Briar' plants, with lower values observed, in general, in plants irrigated with solutions containing Na2SO4.

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Greenhouse rose (Rosa × spp. L.) production is facing the use of poor-quality irrigation waters and regulatory pressures to recycle runoff and drainage effluents. Two experiments (were conducted to evaluate the yield and quality and ion accumulation responses of roses grafted on various rootstocks to increasing salinity stress. In Expt. 1, the scion ‘Bridal White’ grafted on ‘Manetti’, R. odorata (Andr.), ‘Natal Briar’, and ‘Dr. Huey’ were irrigated over four flowering cycles with complete nutrient solutions supplemented with NaCl at 0, 5, and 30 mm. In Expt. 2, plants of ‘Red France’ on ‘Manetti’ and ‘Natal Briar’ were irrigated over six flowering cycles with complete nutrient solutions supplemented with NaCl + CaCl2 (2:1 m ratio) at 0, 1.5, 3, 6, 12, and 24 mm. Salt concentration increases significantly and negatively affected the biomass, cut flower production, and foliage quality of the roses in both experiments, but the responses were modulated by rootstock selection. ‘Manetti’ plants in general sustained better absolute and relative biomass and flower yields, accumulated less Na+ and Cl in its tissues, and showed less toxicity symptoms with increasing salinity than the others. ‘Natal Briar’ also had similar absolute productivity responses as ‘Manetti’ but were afflicted by a significantly different mineral nutrient profile, including higher accumulations and toxicities with Na+ and Cl that led to lower foliage visual ratings. Conversely, the relative yields of plants on ‘Dr. Huey’ and R. odorata were similarly reduced by increasing salinity, but the former had lower Na+ and Cl concentrations in its tissues and better visual scores than the latter, which fared as the worst. A combined analysis of the results suggests that on a productivity basis (biomass and flower yields), greenhouse roses could withstand overall maximum electrical conductivities (i.e., osmotic effects) of applied fertigation solutions of 3.0 ± 0.5 dS·m−1. On the other hand, and considering the aesthetic responses (visual scores) of on-plant and harvested foliage (cut flower shoots), greenhouse rose tolerance to applied Na+ and Cl concentrations (ion-specific effects) could range up to 10 ± 2 mm.

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To enlarge the palette of environmentally-responsible landscape plants, 117 garden rose cultivars were evaluated under minimal input conditions. Other than mulching and irrigation, no other inputs were provided, including no fertilization and no pesticide applications. Plants were established in completely randomized blocks with four reps in the spring of 1998 with data collection beginning in 2000 and continued through 2002. Data on overall performance (an index comprised of flower number, percent of plant covered with flowers and plant growth) and relative chlorophyll content were collected the first and third week of each month from April through October. Disease ratings or incidence ratings were collected for Diplocarpon rosae Wolf (black spot), Alternaria sp. (petal blight) and Sphaerotheca pannosa (powdery mildew). Statistical analysis was performed on the mean data for all dates. `Knockout' was the top rose for overall quality with little or no disease observed, high foliage quality, and continuous flowers from spring until late in the fall. `Knockout' also ranked among the top rose cultivars in terms of overall nutrient concentrations (N, P, K, and Fe) in new growth tissue. Most of the hybrid tea roses such as `Peace' and `Double Delight' died in at least three blocks due to disease and a lack of vigor.

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One hundred sixteen rose (Rosa spp.) cultivars were evaluated under minimal input conditions in north-central Texas for 3 years. Plant quality data included overall plant performance, number of flowers, percentage of bloom coverage, final vigor, and survival. Disease ratings for black spot (Diplocarpon rosae), petal blight (Alternaria alternata), powdery mildew (Sphaerotheca pannosa), and aphid (Myzus spp.) infestations were previously reported. Of the original 116 cultivars, 25 had 50% or higher mortality during the trial. Own-root cultivars performed significantly better than the grafted cultivars and had significantly better survival (P = 0.001). As a class, the Polyantha cultivars exhibited the best overall performance, mean bloom percentage, final vigor and survival, while cultivars in the Hybrid Tea class had the worst performance in all measures. Foliar nutrient content, bloom number, and mean percentage of bloom were not good predictors of overall performance. Of the diseases monitored, black spot was the most severe and was closely correlated to overall performance and final vigor, but was not the only factor determining overall performance. The top five cultivars in mean overall performance were RADrazz (Knock Out™), Caldwell Pink, Sea Foam, Perle d'Or, and The Fairy, in descending order.

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