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Wildflowers are good candidates for water-wise landscapes because many of them are drought-tolerant after establishment. Little information is available regarding whether these herbaceous wildflowers are tolerant to salt stress. Container experiments were carried out in a greenhouse and a shadehouse under semiarid climate conditions to investigate the salt tolerance of six native wildflowers: Saiviafarinacea (mealy cup sage), Berlandiera lyrata (chocolate daisy), Ratibida columnaris (Mexican hat), Oenothera elata (Hooker's evening primrose), Zinnia grandiflora (plains zinnia), and Monarda citriodora (lemon horsemint). In the greenhouse experiment, mealy cup sage, Hooker's evening primrose, and plains zinnia were irrigated with a saline solution with an electrical conductivity (EC) of 1.5 (control, nutrient solution), 2.8, 4.1, 5.1, or 7.3 dS·m-1 for 45 days. All plants survived except for plains zinnia at EC of 7.3 dS·m-1. Shoot dry weights decreased as EC of irrigation water increased for all three species. In the shadehouse experiment (second year), plants of all species (plains zinnia was not included) were irrigated with saline solutions at EC of 0.8 (control, tap water), 2.8, 3.9, 5.5, or 7.3 dS·m-1 for 35 days. Plants were fertilized with slow-release fertilizer in the shadehouse experiment. After 5 weeks of treatment, all plants of lemon horsemint in the elevated salinity treatments, regardless of EC levels, were dead. The visual foliar salt damage rating was lowest for lemon horsemint. Chocolate daisy had low survival percentages and low foliar ratings at EC of 5.5 dS·m-1 and 7.3 dS.m-1. For the other three species, survival percentages were 80% and 90% at EC of 7.3 dS·m-1. Hooker's evening primrose and mealy cup sage had similar low foliar visual ratings at EC of 7.3 dS·m-1, whereas Mexican hat plants had high foliar visual ratings regardless of salinity treatment. All species had similar high uptake of Na+ in shoots, whereas Hooker's evening primrose had slightly higher Cl- concentrations compared with other species. Based on these results, lemon horsemint was most sensitive to salinity stress followed by chocolate daisy. Hooker's evening primrose and mealy cup sage were moderately tolerant and may be irrigated with low salinity water at EC of less than 3.9 dS·m-1. Mexican hat was the most tolerant among the six species. [ABSTRACT FROM AUTHOR]

Texas mountain laurel (Sophora secundiflora) is a native shrub tolerating drought, heat, windy conditions, and alkaline or wet soils. However, its availability is somewhat low and little information is available on nutrient requirement and other culture information. Two greenhouse experiments were conducted to quantify the responses of Texas mountain laurel to different forms and rates of nitrogen (N) fertilizer. In Expt. 1, 1-year old seedlings were treated for 194 days with three NO3:NH4 ratios at 25:75, 50:50, and 75:25 and two rates of N at 100 and 200 mg⋅L-1 in a factorial design. There was no interaction between the N rate and form on any growth parameters. Nitrogen form did not significantly affect shoot dry weight, root dry weight, root--to-shoot ratio, or the total dry weight. There was no significant difference between N rate of 100 and 200 mg⋅L-1 on root dry weight, root-to-shoot ratio, or the total dry weight. The shoot dry weight of Texas mountain laurel fertilized with 100 mg⋅L-1 was higher compared with that of the plants fertilized at 200 mg⋅L-1. The reduced shoot dry weight at N of 200 mg⋅L-1 was the result of the higher substrate salinity. In Expt. 2, seedlings were fertilized with five N rates (50, 100, 150, 200, and 250 mg⋅L-1) for 203 days. Plants watered with 150, 200, and 250 mg⋅L-1 were taller than those fertilized with 50 mg⋅L-1. The shoot height of plants watered with 100 mg⋅L-1 was only significantly different from 50 mg⋅L-1. For rapid growth of Texas mountain laurel, a N rate range of ≈150 mg⋅L-1 was recommended supplied with a combination of NO3-N and NH4-N in the ratios of 0.3 to 3.0. [ABSTRACT FROM AUTHOR]

Bedding plants are extensively used in urban landscapes. As high-quality water supply becomes limited in many parts of the world, the use of recycled water with high salt levels for landscape irrigation is being encouraged. Therefore, information on salt tolerance of bedding plants is of increasing importance. Two experiments were conducted, one in a 25% light exclusion shadehouse in summer (Expt. 1) and the other in a greenhouse in winter (Expt. 2). Plants were irrigated with saline solution at electrical conductivities of 0.8, 2.8, 4.0, 5.1, or 7.4 dS·m-1 created by adding NaCI, MgSO4, and CaCI2 to tap water to simulate the composition of local reclaimed water. In Expt. 1, shoot dry weight (DW) at the end of the experiments was reduced in all species at 7.4 dS·m-1 compared with the control (0.8 dS·m-1). The magnitude of reduction varied with species and cultivars. The salinity thresholds of irrigation water in which growth reduction occurred were 4.0 dS·m-1 for angelonia (Angelonia angustifolia) cultivars and ornamental pepper (Capsicum annuum) 'Calico' and 4.0 to 5.1 dS·m-1 for helenium (Helenium amarum), licorice plant (Helichrysum petiolatum), and plumbago (Plumbago auriculata). Shoot DW and growth index of ornamental pepper 'Black Pearl' and vinea (Catharanthus roseus) 'Rose' decreased linearly as salinity increased. All plants survived in Expt. 1 regardless of treatment, except for ornamental pepper 'Purple Flash'. No visual injuries were observed in Expt. 1 regardless of treatment. Leaf sodium (Na) and chlorine (CI) concentrations varied with species and treatments. Ornamental pepper 'Black Pearl' had the highest leaf CI concentrations at higher salinities compared with other species and cultivars. Leaf Na concentrations in licorice plant and plumbago were in the range of 10 to 30 g·kg-1 DW, higher than those in other species. In Expt. 2, shout DW was reduced by salinity, treatments in ornamental pepper 'Black Pearl', plumbago, and angelonia but not in other species. The three ornamental peppers, 'Black Pearl', 'Calico', and 'Purple Flash', exhibited slight follar injuries on some plants in Expt. 2 as a result of high salinity in the root zone in the highest salinity treatment. Ornamental pepper 'Black Pearl' was most sensitive to salinity, stress. In general, the bedding plants tested in this study are moderately tolerant to salt stress and may be irrigated with saline water up to 4.0 dS·m-1 with little reduction in aesthetical appearance. [ABSTRACT FROM AUTHOR]

Use of reclaimed water to irrigate urban landscapes will likely increase because fresh water supply is diminishing and the population continues to grow in the semiarid southwestern United States. Salt tolerance of two native landscape woody ornamentals, Texas mountain laurel (Sophora secundiflora) and Mexican redbud (Cercis canadensis var. mexicana), was investigated in a greenhouse experiment. Seedlings of the two species were grown in two substrates mixed with composted mulch and a commercial potting mix at two ratios and irrigated with saline solutions at three salinity levels: 1.6 (control, nutrient solution), 3.0, or 6.0 dS*m-1 electrical conductivity (EC). There was no interaction between substrate and EC of irrigation water. Foliar salt damages such as leaf drop, leaf curl, and edge burn were observed in Mexican redbud when the plants were irrigated with solutions at EC of 3.0 and 6.0 dS*m-1. No symptoms were observed on Texas mountain laurel plants, although plants irrigated at EC of 3.0 and 6.0 dS*m-1 were smaller compared with controls. Shoot growth and elongation of both species were reduced by the elevated salinity of irrigation water, and the reduction in Mexican redbud was greater than Texas mountain laurel. Leaf photosynthesis rate and leaf stomatal conductance were also reduced in Texas mountain laurel by the elevated salinity of irrigation water. Tissue Na+ and Cl- concentrations were higher in Texas mountain laurel irrigated with water of elevated salinity. [ABSTRACT FROM AUTHOR]

Salt-tolerant landscape plants are needed for arid and semiarid regions where the supply of quality water is limited and soil salinization often occurs. This study evaluated growth, chloride (Cl) and sodium (Na) uptake, relative chlorophyll content, and chlorophyll fluorescence of three rose rootstocks [Rosa xfortuniana Lindl., R. multiflora Thunb., and R. odorata (Andr.) Sweetl irrigated with saline solutions at 1.6 (control), 3.0, 6.0, or 9.0 dS⋅m-1 electrical conductivity in a greenhouse. After 15 weeks, most plants in 9.0 dS⋅m-1 treatment died regardless of rootstock. Significant growth reduction was observed in all rootstocks at 6.0 dS. ⋅m-1 compared with the control and 3.0 dS.m⋅m-1, but the reduction ih R. x fortuniana was smaller than in the other two rootstocks. The visual scores of R. multiflora at 3.0 and 6.0 dS⋅m-1 were slightly lower than those of the other rootstocks. Rosa odorata had the highest shoot Na concentration followed by R. multiflora; however, R. multiflora had the highest root Na concentration followed by R. odorata. All rootstocks had higher Cl accumulation in all plant parts at elevated salinities, and no substantial differences in Cl concentrations in all plant parts existed among the rootstocks, except for leaf Cl concentration in R. multiflora, which was higher than those in the other two rootstocks. The elevated salinities of irrigation water reduced the relative chlorophyll concentration, measured as leaf SPAD readings, and maximal photochemical efficiency of photosystem II (PSII) and minimal fluorescence (Fo)/maximum fluorescence (Fv/Fm), but the largest reduction in Fv/Fm was only 2.4%. Based on growth and visual quality, R. x fortuniana was relatively more salt-tolerant than the other two rootstocks and R. odorata was slightly more salt-tolerant than R. multiflora. [ABSTRACT FROM AUTHOR]

Ten herbaceous perennials and groundcovers were grown in raised beds-from June to September in a dry, hot desert environment and micro-spray drip irrigated with synthesized saline solutions at electrical conductivity of 0.8 (tap water), 3.2, or 5.4 dS/m. Plant height and two perpendicular widths were recorded monthly to calculate the growth index. Landscape performance was assessed monthly by visual scores. Salinity did not affect the visual scores in Achillea millefolium L., Gaillardia aristata Pursh, Lantana x hybrida 'New Gold', Lonicera japonica Thunb. 'Halliana', and Rosmarinus officinalis L. 'Huntington Carpet' throughout the experiment. Glandularia canadensis (L.) Nutt. 'Homestead Purple' performed better than Glandularia x hybrida (Grönland & Rümpler) G L. Nesom & Pruski. Lantana montevidensis (Spreng.) Brig. had lower visual scores at 5.4 dS/m compared to the control and 3.2 dS/m. Most plants of Rudbeckia hirta L. did not survive when irrigated at 3.2 dS/m or 5.4 dS/m. Shoot biomass of A. millefolium, G. aristata, L. x hybrida, L. japonica, R. officinalis, and V macdougalii was not influenced by the salinity of irrigation' water. Therefore, A. millefolium, G aristata, L. x hybrida, L. japonica, and R. officinalis can be irrigated with non-potable water at salinity up to 5.4 dS/m with little reduction in growth and aesthetic appearance. [ABSTRACT FROM AUTHOR]

A study was conducted to characterize the response of Gaillardia aristata Pursh to salinity (0.8, 2.0 or 4.0 dS/m) and growing media: 100% perlite (Perlite), 100% Sunshine Mix No. 4 (Mix), 1 to 1 (by vol) perlite and Sunshine Mix No. 4 (Perlite Mix), or 1 to 1 Sunshine Mix No. 4 and composted mulch (Mix Mulch). Type of medium did not influence shoot dry weight (DW). However, root to shoot DW ratio was highest for plants grown in Perlite. Shoot DW of plants irrigated with tap water (0.8 dS/m) was higher compared to those irrigated with saline solution at 2.0 or 4.0 dS/m, except for those grown in Mix. Salinity did not alter the root to shoot DW ratio. In general, elevated salinity led to relatively short plants. Plants were taller when grown in Perlite or Mix Mulch with fewer lateral shoots compared to plants grown in Mix and Perlite Mix. Flower bud abortion occurred in plants grown in Mix or Perlite Mix, while this phenomenon was not observed in plants grown in Perlite or Mix Mulch. Overall, plants performed better in Perlite and Mix Mulch than Mix and Perlite Mix. [ABSTRACT FROM AUTHOR]

Abstract: In order to use reclaimed water to irrigate landscape plants and minimize damage and loss, salinity tolerance of commonly used landscape plants needs to be determined and characterized. Eight herbaceous perennials and groundcovers were obtained from a local nursery, transplanted to 2.6-L plastic containers and grown in the greenhouse for 2 weeks before saline irrigation at electrical conductivity (EC) of 0.8 (tap water), 3.2, 6.4, or 12dSm−1 were initiated. Plants were irrigated with measured amount of saline solutions to obtain 30% leaching when approximately 50% water had been depleted. After 12 weeks, four plants in each treatment were destructively harvested and dry weights of shoots and roots were determined. Three Penstemon species (P. eatonii A. Gray, P. pseudospectabilis M.E. Jones, and P. strictus Benth.) and Lavandula angustifolia Mill. at 6.4 and 12dSm−1 and most at 3.2dSm−1 did not survive. Shoot dry weight of Delosperma cooperi (Hook.f.) L. Bolus decreased by 25% at 12dSm−1, but there were no significant differences among the rest of the treatments. All plants of Teucrium chamaedrys L. survived but growth was reduced significantly with lower visual scores as salinity of irrigation water increased. Although growth was reduced in Gazania rigens (L.) Gaertn. as salinity increased, no other signs of stress or injury were observed. Ceratostigma plumbaginoides Bunge had reduced growth at 3.2dSm−1 and higher EC levels compared to the control, older leaves showed reddish pigmentation at 6.4dSm−1, whereas those at 12dSm−1 did not survive. Ion concentrations of shoot and root tissue at the end of the experiment on surviving plants were also affected by salinity levels and varied among species. Among the tested species, D. cooperi and G. rigen indicated a relatively high tolerance to salinity, T. chamaedrys and C. plumbaginoides were moderately tolerant, and the rest were less tolerant. [Copyright &y& Elsevier]

Use of recycled water to irrigate urban landscapes may be inevitable, because the freshwater supply has been diminishing and the population continues to grow in the arid and semiarid southwestern United States. However, little information exists on the performance of landscape plants irrigated with nonpotable water. Two greenhouse studies were conducted during the summer and the fall to characterize the relative salt tolerance of five herbaceous perennials by irrigating the plants with a saline solution at an electrical conductivity (EC) of 0.8 dS·m-1 (tap water), 2.0 dS·m-1, or 4.0 dS·m-1. In the summer study, after 10 weeks of treatment, Achillea millefolium L., Gaillardia aristata Foug., and Salvia coccinea Juss ex J. had an aesthetically acceptable appearance for landscape performance (visual quality scores of 4 points or more), whereas Agastache cana (Hook.) Woot. & Standl. and Echinacea purpurea (L.) Moench had relatively low tolerance to salinity. Dry weight of shoots ofA. miilefolium, A. cana, and (7. arstata was lower at elevated salinity levels. In the fall study, A. millefolium, E. purpurea, {7,. arstata, and S. coccinea had acceptable growth and visual quality at elevated salinity levels, whereas A. cana had lower quality and reduced growth. Dry weight of shoots was lower in G. arstata and A. millefolium at an EC of 2.0 dS·m-1or 4.0 dS·m-1. Leaf osmotic potential of all species in the summer experiment was significantly lower at higher salinity compared with the control. In the fall experiment, leaf osmotic potential in A. millefolium, E. purpurea, and G. aristata at 4 dS·m-1 was lower compared with lower salinity treatment and the control. Leaf osmotic potential in the fall was higher than that of the same species at the same salinity level in the summer experiment, indicating that plants in the fall were less stressed than in the summer. Combined the results from both experiments, the authors concluded that A. millefolium, G. arstata, and S. coccinea had a relatively high salt tolerance (as much as 4 dS·m-1 of irrigation water under greenhouse conditions) among the tested species, whereas A. cana and E. purpurea were not tolerant to salt and should not be irrigated with low-quality water. [ABSTRACT FROM AUTHOR]

Use of recycled water to irrigate urban landscapes and nursery plants may be inevitable as fresh water supplies diminish and populations continue to grow in the arid and semiarid southwestern United States. Lupinus havardii Wars. (Big Bend bluebonnet) has potential as a cut flower and Lupinus texensis Hook. (Texas bluebonnet) as a bedding plant, but little information is available on salt tolerance of these species. A greenhouse study was conducted to characterize the growth in response to various salinity levels. Plants were grown in 10-L containers and drip-irrigated with synthesized saline solutions at electrical conductivity levels of 1.6, 3.7, 5.7, 7.6, or 9.4 dS⋅m-1. Although shoot growth of L. texensis was reduced as salinity levels increased, it was visually acceptable (without any visual injury) when irrigated with salinity levels of less than 7.6 dS⋅m-1. All plants survived at 7.6 dS⋅m-1, whereas only 15% did at 9.4 dS⋅m-1. In contrast, L. havardii had leaf injury at 5.7 dS⋅m-1. No plants survived at 9.4 dS⋅m-1, and only 7% plants survived at 7.6 dS⋅m-1. In addition, growth of L. havardii was significantly reduced and plants were shorter at elevated salinity levels. Cut raceme yield of L. havardii decreased at salinity levels greater than 3.7 dS⋅m-1. However, no difference in cut raceme yield was observed between the control and 3.7 dS⋅m-1, although shoot growth was reduced. Overall, L. texensis was more salt-tolerant than L. havardii. [ABSTRACT FROM AUTHOR]