Plant selection for landscaping can have both immediate and prolonged consequences. Proper selection can create attractive spaces that provide shade for sustainable building design while improving soil conditions and promoting biodiversity. Inappropriate plant choice, however, can have the reverse effects of not contributing to outdoor comfort and visual appeal while being damaging to soil and local biodiversity. Another major impact of plant selection, which we focused on, is their water consumption. It may seem obvious not to plant wet tropical trees in west Texas desert climate, but even subtle choices can make large differences when scaled up to the size of a college campus.
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Permaculture
Permaculture is a system of agricultural and landscape design that emphasizes the use of the natural ecosystem and all its functions to achieve maximum benefit to the environment. A key component of permaculture landscape design is the selection and layering of regional plants. These plants are inherently adjusted to local climate and precipitation, having evolved and thrived for millions of years in such conditions. The incorporation of native, or naturalized, plants in green spaces helps save on extraneous watering non-native plants would demand, while creating an atmosphere that celebrates local ecology.
The following is a list of low-water plant species that are native, or have been adapted, to the north and central Texas regions. This list was compiled with the help of Curren Rehm (29) of Permaculture Design©.
The following is a list of low-water plant species that are native, or have been adapted, to the north and central Texas regions. This list was compiled with the help of Curren Rehm (29) of Permaculture Design©.
More resources are available on websites such as Texas Smartscape which has a plant search engine (30). To find appropriate plants just select the relevant parameters, such as plant type, light requirement and water demand, and a list will be generated.
Xeriscaping
Overview
Xeriscaping is a method of gardening that intentionally reduces or eliminates the need for watering. This landscaping technique relies heavily on the use of native, low-water plants as well as efficient irrigation to cut water losses due to over-watering and evaporation.
Several principles are central to utilizing low-water landscaping (31):
- Sound landscape planning and design
- Limitation of turf to appropriate, functional areas
- Use of water-efficient plants
- Efficient irrigation (drip instead spray irrigation)
- Soil amendments
- Use of mulches
- Appropriate landscape maintenance
Research
The South Nevada Water Agency (SNWA) conducted a five-year study of water savings associated with south Nevada residents converting to Xeriscaping (31).
A central concern to switching over to Xeriscaping is the aesthetic appeal. Green lawns are a visual staple of many American communities and people may have a hard time substituting them for different landscapes. Furthermore, because of its original use in arid regions, Xeriscaping has gained a reputation for offering dry and boring views filled with cacti and gravel. Although Xeriscaping, by default, is not meant to be the same lush landscape we are familiar with throughout Houston, its visual impact can be appealing if care is taken in the design process.
A study conducted in Melbourne, Australia assessed the visual attractiveness of several types of residential landscapes in comparison to their water demand (32). Study participants were shown simulated images with six different types of lawn and were asked to rate each in categories such as visual attractiveness, expected water and financial requirements, and overall desirability. It was found that the Xeriscape, which consisted of paving and pebbles with succulents and shrubs, was rated second to last in attractiveness. These ratings, however, exhibited the largest standard deviation, signifying divided opinions on the attractiveness of Xeriscape. The study concluded that the overall desirability front yards was not correlated with their water use requirements, but with their attractiveness.
- The study found that Xeriscaping could save a significant 55.8 gal/sqft (76%) in comparison to turf grass.
- Xeriscaping reduced winter-to-summer peak demand ratios by 48%. While winter-to-summer ratio of turf residencies was 1:4.8, that of Xeriscape residencies was 1:2.5.
- Xeriscaping was also found to reduce the cost associated with yard maintenance, with reported average annual reductions of 26.4 hours of labor and $206 in direct maintenance in comparison to turf yards.
A central concern to switching over to Xeriscaping is the aesthetic appeal. Green lawns are a visual staple of many American communities and people may have a hard time substituting them for different landscapes. Furthermore, because of its original use in arid regions, Xeriscaping has gained a reputation for offering dry and boring views filled with cacti and gravel. Although Xeriscaping, by default, is not meant to be the same lush landscape we are familiar with throughout Houston, its visual impact can be appealing if care is taken in the design process.
A study conducted in Melbourne, Australia assessed the visual attractiveness of several types of residential landscapes in comparison to their water demand (32). Study participants were shown simulated images with six different types of lawn and were asked to rate each in categories such as visual attractiveness, expected water and financial requirements, and overall desirability. It was found that the Xeriscape, which consisted of paving and pebbles with succulents and shrubs, was rated second to last in attractiveness. These ratings, however, exhibited the largest standard deviation, signifying divided opinions on the attractiveness of Xeriscape. The study concluded that the overall desirability front yards was not correlated with their water use requirements, but with their attractiveness.
On-campus Implementation
Certain areas of the UH campus are already implementing this landscaping method. A prominent example is the recent renovation done in front of the Moore’s School of Music. Much of the turf was replaced with gravel, and some trees with shrubs and mulch.
More aspects of Xeriscaping could be incorporated into the UH Landscape Guideline. The guidelines under Planting (section 6.8) convey the importance of native species that create a regional and indigenous character, but there is not yet a specific list of such plants. Energy-sensitive and environmentally friendly irrigation is mentioned without further explanation or criteria.
Conclusion
These investigations reveal that Xeriscaping, as a method of water-conservative landscape design, has the potential to be applied in many areas of the country that experience water shortages or that are conscious of the need to save water. It appears that people would be more inclined to accept such low-water landscapes if they are well designed and visually appealing. This matter may require further promotion, education and a cultural change in perception.