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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.

The effect of drought on the growth and gas exchange of six bedding plant species—agastache [Agastache urticifolia (Benth.) O. Kuntze `Honeybee Blue'], dusty miller (Cineraria maritima L. `Silverdusty'), petunia (Petunia ×hybrida `Wave Purple'), plumbago (Plumbago auriculata Lam. `Escapade'), ornamental pepper (Capsicum annuum L. `Black Pearl'), and vinca [Catharanthus roseus (L.) G. Don `Titan']—was quantified under greenhouse conditions. Seeds were sown in January and seedlings were grown in the greenhouse until 18 Apr., when two irrigation treatments—drought (D, ≈18% volumetric moisture content at reirrigation) and control (C, ≈25% volumetric moisture content at reirrigation)—were initiated. Leaf net photosynthetic rate (P_n), stomatal conductance (g_s), and transpiration (E) were determined in response to a range of substrate moisture content (from ≈5% to 30% by volume) and temperature (from 20 °C to 40 °C). Dry weight of agastache, ornamental pepper, and vinca was unaffected by drought, whereas that of other species was reduced. Leaf area of plumbago and height of plumbago and vinca were reduced by drought. As substrate moisture content decreased from 25% to 10%, P_n, E, and g_s decreased linearly in all species except petunia and plumbago. Leaf net photosynthetic rate of all species declined as leaf temperature increased from 20 °C to 40 °C. In contrast, E of all species, except petunia, increased as temperature increased. Transpiration rate of petunia increased as temperature increased from 20 °C to 30 °C, and then decreased between 30 °C and 40 °C. Although petunia had the highest P_n among the tested species, its P_n and g_s declined more rapidly compared with the other species as temperature increased from 20 °C to 40 °C or as substrate moisture content decreased, indicating that petunia was most sensitive to high temperature and drought.

Ornamental chile peppers are popular bedding plants. As high-quality water supply becomes limited in many parts of the world, alternative waters such as municipal reclaimed water is encouraged to be used for landscape irrigation. The purpose of this study was to assess the relative salt tolerance of 10 cultivars of ornamental chile peppers by irrigating the mature plants with saline solutions and germinating seeds in saline substrate in a greenhouse. In the mature plant salt tolerance experiment, plants were irrigated with nutrient solution (no addition of salts, control) or saline solution at electrical conductance (EC) of 4.1 dS·m⁻¹ or 8.1 dS·m⁻¹ for 8 weeks. Plants in the EC of 4.1 dS·m⁻¹ treatment did not have any foliar salt damage regardless of cultivar. At EC of 8.1 dS·m⁻¹, ‘NuMex Memorial Day’ had the most severe foliar salt damage, whereas ‘NuMex April Fool’s Day’, ‘NuMex Cinco de Mayo’, ‘NuMex Thanksgiving’, and ‘NuMex Twilight’ had little or no foliar damage. Shoot dry weight (DW) reduction at EC of 8.1 dS·m⁻¹ compared with control was smallest in ‘NuMex Thanksgiving’ (15%), whereas ‘NuMex Memorial Day’ had the greatest reduction of 74% followed by ‘NuMex Christmas’ of 61%. The highest shoot DW reduction in ‘NuMex Memorial Day’ coincided with lowest visual score, indicating that this cultivar was the least tolerant to salinity. The leaf Na⁺ and Cl⁻ concentrations increased dramatically with increasing EC of the irrigation water in all cultivars. The highest Na⁺ concentration of 10.9 mg·g⁻¹ DW at EC of 8.1 dS·m⁻¹ was observed in ‘NuMex Christmas’. The highest Cl⁻ concentration at EC of 8.1 dS·m⁻¹ was found in ‘NuMex Memorial Day’ with 64.8 mg·g⁻¹ DW, which was four times higher than the control. In the seedling emergence experiment, seeds of the 10 cultivars were germinated in substrate either moistened with reverse osmosis water (EC ≈0) or saline solution at EC of 17.1 dS·m⁻¹. ‘NuMex Christmas’ and ‘NuMex Memorial Day’ had the lowest relative seedling emergence index, indicating that these two cultivars were the least tolerant to salinity during the seedling emergence stage. ‘NuMex Thanksgiving’ and ‘NuMex Cinco de Mayo’ had the highest relative seedling emergence index. Combining the results from both experiments, we concluded that ‘NuMex Cinco de Mayo’ and ‘NuMex Thanksgiving’ were the most tolerant cultivars, whereas ‘NuMex Christmas’ and ‘NuMex Memorial Day’ were the least tolerant ones.

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 Wats. (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.

Chile peppers are economically important crops in southern regions of the United States. Limited information is available on irrigation management with low-quality water or on salt-affected soils. The objective of this study was to determine the relative salt tolerance of 20 genotypes of chile peppers. In Expt. 1, seeds of selected pepper types (Anaheim, Ancho, Cayenne, Paprika, Jalapeño, Habanero, and Serrano) were germinated in potting mix and seedlings were grown in 2.6-L pots. Six weeks after sowing, salinity treatments were initiated by irrigating plants with nutrient solutions of different electrical conductivities (ECs): 1.4 (control), 3.0, or 6.0 dS·m⁻¹. After 1 month of initiating treatments, shoots were harvested and dry weights were determined. All plants survived and no visual salt injury was observed regardless of pepper variety and treatment. There were no statistical differences between control and saline solution treatments in final height and shoot dry weight of Habanero 1, ‘Early Jalapeño’, ‘AZ-20’, ‘NuMex Joe E. Parker’, and ‘NuMex Sandia’. In Expt. 2, seeds of 20 genotypes were directly sown in 2.6-L containers filled with loamy sand. Saline water irrigation was initiated 37 days after sowing by irrigating plants either with saline (nutrient solution based, similar to Expt. 1) or nutrient solution (control). More than half the genotypes did not have 100% survival in the salinity treatment. Ancho 1, Ancho 2, Cayenne 1, ‘Early Jalapeño’, and ‘AZ-20’ had 100% survival regardless of salinity treatment. No plants of ‘TAM Mild Habanero’ survived when irrigated with saline water and less than half of the plants survived in the control. The relative tolerance of chile genotypes to salinity varied with substrate in some genotypes. From the combined results of the two experiments, the 20 pepper genotypes were ranked for salt tolerance based on seedling survival, visual quality, and growth. ‘Early Jalapeño’ and ‘AZ-20’ were relatively tolerant to salinity among the 20 genotypes, whereas ‘TAM Mild Habanero’ and ‘Ben Villalon’ were sensitive. Ancho 1, Ancho 2, Cayenne 1, and Cayenne 2 also had relatively high tolerance based on survival and visual quality, although shoot growth was reduced significantly.

Relatively little work has been done to determine the water requirements of ornamental plants. To meet this need, five woody ornamental species including Abelia grandiflora `Edward Goucher', Buddleia davidii `Burgundy', Ilex vomitoria `Pride of Houston', Euonymus japonica, and Nerium oleander `Hardy Pink' were investigated to determine their water use and crop coefficients. Parallel experiments were conducted by growing the shrubs both in 56-L (15 gal) drainage lysimeters and in aboveground 10-L containers. Water use per plant, crop coefficients, and overall growth parameters differed by species and culture system. Of the five species tested, Buddleia and Nerium had higher water use per plant in the lysimeters than in the containers. There was no significant difference in water use per plant for Abelia, Euonymus, and Ilex between the two culture systems. Crop coefficients and growth indices of Abelia, Euonymus, and Ilex were statistically similar between the two systems. The growth index of Buddleia and Nerium was much higher in the lysimeters than in the containers. Abelia and Euonymus had more growth in the containers than in the lysimeters while Ilex had slightly larger leaf area in the lysimeters than in the containers. The culture system did not affect the water use per unit leaf area of all species. Therefore, our results indicated that by quantifying the leaf area, the plant water use in the two culture systems is convertible.

High soil salinity often results in poor stand establishment, reduced plant growth, and reduced yield of many horticultural crops such as peppers (Capsicum annuum). We investigated the effects of soil salinity and soil type on seedling emergence and growth of four commercial peppers (‘NuMex Joe E. Parker’, ‘NuMex Nematador’, ‘NuMex Primavera’, and ‘Jupiter’) in greenhouse experiments. Seeds were sown in either a loamy sand or a silt loam soil in pots and irrigated with saline solutions at electrical conductivity of 0.9 (tap water), 3.0, or 6.0 dS·m⁻¹ (Expt. 1) or at 0.0 [reverse osmosis (RO) water], 0.9, or 1.5 dS·m⁻¹ (Expt. 2). No seedling emergence was observed in treatments irrigated with 3.0 or 6.0 dS·m⁻¹ solutions. The salinity at the top soil layer increased linearly with time when subirrigated with tap and saline solutions in both soil types, whereas no substantial increase in soil salinity was found when subirrigated with RO water or overhead irrigation with tap water. Salt accumulation at the top soil layer was greater in loamy sand than in silt loam. Seedling emergence percent subirrigated with RO water ranged from 70% to 80% in loamy sand and 45% to 70% in silt loam, depending on pepper cultivars. When subirrigated with tap water and saline solutions, the emergence percent ranged from 0% to 60%, depending on pepper and soil types. In Expt. 3, seedlings were germinated in commercial potting mix and grown in 1.8-L pots containing commercial potting mix. Saline solution treatments of 1.4 (control, nutrient solution), 2.1, 2.9, 3.5, or 4.2 dS·m⁻¹ were initiated when seedlings had 11 to 13 leaves. Five weeks after initiating saline water irrigation, the reduction in shoot dry weight was greater in ‘Jupiter’ and ‘NuMex Primavera’ as compared with ‘NuMex Joe E. Parker’ and ‘NuMex Nematador’, but the differences were small.