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Home HortTechnology Shrubs Recommended for Highway Slopes
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COMO, ITALY—Shrubs are commonly used in urban landscapes to protect sloped areas from erosion and provide visual interest around highways and in city environments. In Europe, where only a few types of shrubs are currently used by city planners, researchers are looking for new shrubs that can withstand the challenges of urban life and bring new variety to cityscapes.

According a study published in HortTechnology, current trends in urban landscaping require the use of low-maintenance shrubs because of the limited supply of irrigation water in most urban greenspaces. "It is also necessary to limit weed competition with transplanted plants to reduce the need for weeding and chemical treatments," said the study's lead author Gabriele Amoroso. Amoroso and a team of horticultural researchers performed experimental trials near Como, Italy, to evaluate the performance of 25 shrub species grown on slopes.

The study featured the use of two mulches—biodegradable textile and polypropylene fabric—compared with a bare soil control to evaluate the influence of weeds on plant growth and weeding time. To simulate urban conditions the scientists used no pruning or disease control methods during the 3-year trial.

"Our results showed that the highest growth (measured by height and biomass) was detected in mulched plots, probably because of both limited weed competition for water and nutrients and lower water loss by evaporation" Amoroso said. "Plants grown in bare soil showed higher root density and finer roots compared with mulched plants; this may be explained by the necessity of the plant root system to explore the soil to reach for water." The researchers recommended that bare soil and fast growing shrubs be used to limit weed competition and create optimal slope greening.

The study also recommended the shrubs fuzzy deutzia and virginal mock orange for planting on slopes along roads and highways. "Among the species we tested, these two shrubs showed a higher number of desirable qualities: fast ground-covering ability, reduced hand-weeding time, plant shoot biomass unaffected by soil management, high root density, and high specific root length," the researchers said.


The complete study and abstract are available on the ASHS HortTechnology electronic journal web site:

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at


Original Article:

Evaluation of Shrubs for Side Slope Greening and Protection in Urban Landscape
Gabriele Amoroso, Piero Frangi, Riccardo Piatti, Alessio Fini, Francesco Ferrini, and Marco Faoro
HortTechnology 21:359–366. [Abstract][Full Text][PDF]

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