Site planting is an important part of most construction projects. When done correctly, planting can add the final touch to a project. Plants may be valued for their aesthetics, but they are living things, and have specific requirements, including nutrition, water, and sun. Failure to meet these basic requirements can be fatal.
Often when site plantings fail, the designer blames “the lack of adequate maintenance.” However, it is the designer’s responsibility to understand the site constraints and maintenance capabilities of the owner and provide appropriate ideas.
At one commercial site in Connecticut, poor plant specifications led to mass dieback and many problems. Chief among the issues was the planting of large shade trees under utility wires, leading to severe pruning. Beyond the obvious aesthetic issues, this led to tree decline. In other areas, the lack of mulched beds resulted in mowers clipping the bark of trees, inviting pests and disease infestations. Where shade-tolerant shrubs were needed, plants with a requirement for full sun were specified.
Most planting failures can be traced to the wrong plant selection by the design professional, who failed to meet one or more of the following basic requirements.
Planting soils are composed of sand, silt, and clay, and are generally categorized as one of 12 types by the U.S. Department of Agriculture–Natural Resources Conservation Service (USDA-NRCS) soil texture classification triangle. Sandy soils will be well drained, and clay soils are often wet. Soil composition also affects the availability of nutrients, as sandy soils leach away life-giving resources.
A common cause of failure with street trees is a lack of adequate growing soil. Formulas are available to determine the minimum volume for specific trees, but rarely is this criteria met. The old adage “a $50 hole for a $5 tree” is still a surprisingly accurate ratio.
Categories are full sun, part shade, and full shade. Heavy shade is the most difficult condition to address, as few plants have the ability to thrive without at least a few hours of sun a day.
In a vast majority of commercial planting applications, maintenance will not be robust, so plants need to be able to survive drought conditions or long periods without supplemental watering.
It is obvious plants grow. One common problem is with large trees planted under power lines. These trees will often be heavily pruned to avoid possible issues during storm events. This leads to the decline and removal of the tree.
Insect and disease resistance
Plants can quickly succumb to diseases and pests problems if planted in the wrong environment. Many insects and diseases are opportunists, taking advantage of plants that are stressed and unhealthy.
Choosing the right plant for the right environment is key and the result of applying all these constraints in a matrix as well as finding a plant meeting not only the design requirements (shape, color, texture, and size), but the environmental conditions as well. It is the responsibility of the landscape designer to address the specific environmental conditions and maintenance resources of each site.
The opinions expressed in Failures are based on the authors’ experiences and do not necessarily reflect those of The Construction Specifier or CSI.
Mary F. Dehais, CANP, is a landscape designer with To Design in New Britain, Connecticut, specializing in sustainable site and planting design. She can be reached at firstname.lastname@example.org.
W. Phillips Barlow, PLA, AICP, is the founding principal of To Design. He can be reached at email@example.com.