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Environmental and human health requirements necessitate replacing chemical herbicides with natural ones for weed control. Allelopathy is a form of interaction among plants that may assist in producing natural herbicides, but less research has been conducted in this important area. Allelopathic effects of extracts of five drought-tolerant plant species widely used in urban landscapes were examined using five completely randomized design experiments with four replications. The species were Rosmarinus officinalis, Lavandula officinalis, Salvia sclarea, Atriplex halimus, and Atriplex canescens. The plant species' soluble extracts were prepared at 0, 2.5, 5, and 7.5%. The seeds' germination percentage and rates of Taraxacum officinale, Conyza canadensis, and Tragopogon major were measured daily after being affected by these extracts. Increasing the concentrations of all the extract types was associated with germination percentages and rate declines. The most outstanding allelopathic effects were related to Atriplex halimus and Salvia sclarea extracts, respectively. Tragopogon major was considered the most sensitive weed species in reducing its germination rate when affected by the landscape plant extracts, except for R. officinalis extract. The reduction in germination percentage of T. major and C. canadensis under A. halimus extract compared to the control was the highest. A. halimus and S. sclarea extracts can be used as natural weed controllers for important weeds such as Taraxacum officinale.

High temperatures, low average rainfall, drought, and high evapotranspiration are limiting factors in arid lands. Therefore, when constructing landscapes (green spaces) in these regions, strategies should be developed to mitigate these climatic influences. One practical strategy is utilizing different types of mulches on the surface of the soil. This study was conducted as a randomized complete block design experiment with four replications during 2014 and 2015 to examine the performance of organic and inorganic mulches as non-living mulches and ground cover plants as living mulches. Ground cover plants were Carpobrotus sp., Potentilla reptans, Vinca minor, Frankenia sp. and a mixed turfgrass. Non-living mulches were turfgrass clippings, wood chips, sawdust, gravel, rubble and scoria (volcanic rock). Bare soil was used as the control treatment. The results demonstrated the application of mulches could modify soil temperature at 5 and 15 cm depths in different seasons of the year. The living mulches especially Carpobrotus sp. and turfgrass reduced the temperature more than the non-living mulches. The soil covered with sawdust and wood chips preserved soil moisture content over the soil covered with other types of mulches. It would appear the selected mulches could decrease the irrigation intervals through increased water holding capacity of the soil. The outcomes of this research could assist landscape managers operating in extreme climate conditions of arid and semi-arid regions to advance the management of soil moisture and temperatures with the objective to improve sustainability.

Creating sustainable landscapes especially in arid climates is a significant challenge. To achieve sustainable landscapes, some strategies such as using native plants and soil mulches have been suggested. This study aimed to examine the quality and growth response of the native tall fescue (Festuca arundinacea Schreb.) compared with the corresponding commercial cultivar (Festuca arundinacea ‘Jaguar’) under different planting mulches in their planting and early growth stage in arid climate Mashhad city located in the northeast of Iran. Seeds of commercial cultivar and native species of Festuca arundinacea were sown in a sandy loam texture soil and four mulch treatments including vermicompost, leaf compost, cow manure and sand as control, were applied to cover the seeds. The result showed that the native species had greener color and narrower leaves compared to the commercial cultivar but its other NTEP (National Turfgrass Evaluation Program) traits including density, uniformity, establishment, softness of grass surface, quality after clipping, and total quality was lower than that in the commercial cultivar. Using vermicompost as the planting mulch (top dressing or cover mulch at the time of planting of the turfgrass) significantly improved all of the traits in the native species. Vermicompost increased the percentage of grass coverage, clipping dry weight, and the plant height and decreased the leaf width of plants and number and percentage of weeds. Utilizing native species of tall fescue with vermicompost as the planting mulch can promise as quality lawn as their commercial cultivar for native urban landscaping in Iran.

Considering a large number of cities located in arid and semi-arid climatic regions of the world with limited water resources, reducing water consumption and maintenance costs is an important research and implementation priority in urban landscaping. In other words, reducing the high costs of irrigation, increasing water use efficiency and reducing weed competition are important factors in achieving sustainable green spaces in arid and semiarid regions. Application of mulches is one of the suggested strategies for maintaining bed moisture and weed control. In this research, the effects of organic and inorganic mulches on the performance of the flowering plant of Blanket flower (Gaillardia sp.) were investigated in the arid climate city of Mashhad located in the northeast of Iran. The experiment was conducted as a randomized complete block design with three replications. The four mulch treatments included wood chips, scoria, pine leaves, polyethylene as a layer mulch, and no mulch as the control. The polyethylene mulch inhibited the weed growth up to 100%, and other mulch types also significantly reduced the percentage of the weed coverage (p≤0.01). Application of pine leaves delayed the flowering for seven days while polyethylene caused an early flowering to six days compared to the control. Using different mulch types in water shortage conditions of urban landscapes in arid and semi-arid regions is recommended.

Application of green walls still has not attracted interest among the contractors and people, and this can be due to poor growing performance of the plants on these systems. This study investigated the effect of four growing media types (30% cocopeat + 65% perlite + 5% vermicompost, 30% soil + 65% perlite + 5% vermicompost, 30% mushroom compost + 65% perlite + 5% vermicompost and regular soil as the control) on the performance of three plant species (Frankenia thymfolia, Vinca minor, and Potentilla sp.) on green walls under arid climate of Mashhad city in Iran. In the control growing medium with no organic matter, Frankenia maintained the highest moisture and the lowest temperature compared to the other growing media types. The growing media did not affect the root and shoot fresh and dry weight and leaf relative water content of the Frankenia. Vinca minor in the cocopeat and mushroom compost produced the highest root fresh and dry weight; however, changing to the growing media types enriched with organic matter content did not affect the shoots fresh and dry weight of this plant type. The growing media containing organic matters compared to the control growing medium, improved relative water content of the Potentilla leaves. The growing media containing organic matters, especially mushroom compost, had positive effects on improving the growth performance of the green walls, through maintaining the moisture content of the media, and thus the relative water content of the leaves, which enhanced vitality of the plants.

Creating water-conserving turfgrasses using superabsorbents in soil is a challenge especially in arid environments because their related soil and plant’s behavior is still less known. This research investigated soil moisture content and physiological characteristics of Lolium perenne L. ‘Chadegan’ (perennial ryegrass) and Festuca arundinacea (tall fescue), in the absence (control treatment) or presence of four superabsorbent types. The superabsorbents were Zeolite (zero and 10% wt), Bentonite (zero and 6%wt), Aquasorb (zero and 6 g/m2) and Boloorab (zero and 50 g/m2). The experiment was factorial based on a randomized complete block design with four replications. A one-month stop on irrigation occurred after the first five-month full irrigation regime to simulate drought stress conditions. The results showed tall fescue had higher leaf relative water content, lower relative electrolyte leakage and lower relative saturation deficit than that in perennial ryegrass after applying the drought stress. However, tall fescue had higher chlorophyll content than this factor in the ryegrass. Aquasorb and then Bentonite were able to improve the fresh weight and dry weight in roots and shoots under drought stress conditions compared to the control treatment. Using Aquasorb was associated with better physiological characters in the turfgrasses and higher water content in the soil. Overall, under drought stress conditions, planting tall fescue in a soil containing Aquazorb promised a better quality turfgrass for urban green spaces.

Application[Editor 321] of biotic growth regulators (e.g. humic components) and appropriate mulches is recommended to improve turfgrass quality especially in arid andsemi-arid climate zones. However, limited number of studies have investigated their effect on lawn establishment. To investigate the effect of humic acid (HA) and selected mulches on characteristics of Festuca arundinacea in its planting stage, a factorial experiment based on a completely randomized block design with three replications was performed. The first factor was mulch types including vermicompost, leaf compost, cow manure,[Editor 322] and sand (control) which were used to cover the seeds. The second factor was a HA solution (100 ml l-1) sprayed monthly over the period of the experiment. Plant height, fresh and dry weight of lawn clippings, photosynthetic index, leaf texture, and overall turfgrass quality were measured. Spraying HA significantly improved the measured factors except the dry weight and photosynthetic index of the plants. Among the mulches, vermicompost provided better impressions on improving the characteristics of this turfgrass species including 48% increase in fresh weight, 18% increase in height, 48% increase in total quality, and 10% reduction in leaf width of the turfgrass. This research can assist in developing knowledge for having high quality lawns in urban landscapes of arid and semi-arid environments.

Developing strategies to tackle water stress in lawns in arid climate regions is significantly important. In such conditions, using growing media amendments as well as native plants can relieve drought stress in different growing stages of the plants. This study was carried out to investigate the effects of some types of soil amendments on the emergence and early seedling establishment of tall fescue (Festuca arundinecea Schreb ‘GazBorkhar ecotype’) under water stress conditions. The experiment was performed in a factorial trial based on a completely randomized design with three replications. The first factor, water stress, was applied based on field capacity (FC) at three levels (80% FC (control), 60% FC and 40% FC). The second factor, growing media amendments, was applied at nine levels of municipal solid waste (MSW), vermicompost (5% and 10% w/w), Stockosorb® (1% and 3% w/w) or zeolite superabsorbent (4% and 8% w/w) which were mixed with loam soil, and the loam soil was used as a control treatment. Theresults showed that using an irrigation system at 60% FC during seed emergence and early seedling growth did not reduce the quality of the turf grass, and also, in many cases, led to a higher quality lawn compared to the control, leading to water saving in turf grass management. Using MSW and manure vermicompost as soil amendments could maintain soil moisture and water supplement for the improvement of morphological, physiological and visual quality of this ecotype of Festuca arundinacea Schreb.

Mulches are relatively new landscape components and are becoming recognized for their environmental and aesthetic outcomes on urban landscapes especially in arid environments. However, the effects of mulches on landscape plants have not been extensively discussed. This study examined the effects of organic and inorganic mulches on the performance of a widely used herbaceous drought tolerant flowering plant, Zinnia elegans, toward low maintenance landscaping. This study was designed as a randomized complete block design with three replications. Four widely commercially available and utilized mulches, including wood chips, pine needles, scoria (volcanic stone) and black polyethylene were used as the treatment mulches. The study contained plots with only bare soil as the control. The results showed that utilizing the selected mulches demonstrated positive effects on the plant growth, and increased the fresh and dry weight of shoots (p