Swale Landscaping Recommendations
Purpose of Swales
Swales are low shallow areas located between the travel way and resident’s homes and/or sidewalks. Swale areas are part of the City’s public right-of-way; however, residents adjacent to the locations are responsible for maintenance and upkeep. Historically, swale areas have been the primary means to address water runoff and drainage within residential streets. Often swales are designed with slight grades to divert water runoff towards drains. Within the neighborhood streets, swale areas are often used for supplemental parking, which results in damaged vegetative areas and unrest from neighboring residents responsible for their upkeep. Excessive car parking in swales also results in compacting soils so densely that water cannot percolate properly through the soil down to the water table, therefore aggravating water ponding on streets and sidewalks. However, the City’s Public Works Department recommends swale planting solutions to promote lush landscaping, deter vehicles from parking within these areas, and serve to provide adequate drainage.
To promote lush landscaping within swale areas and deter vehicles from parking, the Public Work’s Department has developed three options for residents to maintain the grass swale areas. The three options are listed below.
Option 1 (Preferred Option): Grass
- Maintain grass in swales using proper turfgrass management practices, as shown in Figure 3. Within a 3-foot ring around the street trees, property owners may plant non-woody (herbaceous), low growing plants of their choice as long as the plants are maintained at a maximum height of 24”.
- No Permit is required
- Decompaction and planting cost: $500 to $1500 (depends on size)
Option 2: Swale Plantings
- In heavily shaded areas, such as under Banyan trees, where proper turfgrass management is not a practical solution to maintain grass, up to 100% of the swale area may be planted with low 18”-24” tall non-woody (herbaceous) groundcover plants such as Liriope, as shown in Figure 4, with an approved Public Works permit. Swale plantings are intended as an alternative to grass where grass cannot grow
- Public Works Department permit application is required (see swale permit package) but no Permit Fee (county and state roads have additional requirements)
- Cost: $500 to $1,500 (depends on size)
Option 3: Swale Plantings and Decorative Crushed Stone
- In locations where proper turfgrass management in heavily shaded areas and management of excessive parking are not practical solutions to grow grass in the swale, decorative crushed stone and low, non-woody landscape plants, such as Burle Marx Philodendron, as shown in Figure 5, can be allowed with an approved Public Works permit, a Restrictive Covenant Agreement, and a Certificate of Liability Insurance naming the City of Coral Gables as an additional insured.
- Public Works Department permit application is required (see swale permit package), but no Permit Fee (county and state roadways have additional requirements).
- Restrictive Covenant Agreement is required. This covenant is executed with the City attorney’s office prior to submitting the permit application to the Public Works Department.
- Certificate of Liability Insurance naming the City of Coral Gables as an additional insured is required
- Cost: $1,000 to $3,000 (depends of size)
Fifty-eight swale permits have been approved since the inception of the program, but many more permit applications have been submitted and are in review. Please note, all residents are required to maintain and pay for the options listed above, while the City assists in the permitting and inspection process for installation.
If you would like to grow grass below large shade trees, you have several options to get better results:
- You can increase the amount of sunlight reaching the turf by selectively pruning trees. Be aware that this is a temporary solution because the trees will continue to grow over the years.
- You can choose a grass that will tolerate some shade. Among the St. Augustine varieties available, Palmetto is considered one of the most shade tolerant. However, it won’t grow in heavy shade. Also, when replacing sod, is important to remove the previous layer of sod and loosen up the soil to prevent soil compaction that could also kill your grass.
- Grass growing in shaded areas should be mowed at a slightly higher setting on the lawn mower than normally recommended. This allows the leaf blades to grow longer, providing more surface area to absorb what light is available and produce food through photosynthesis. St. Augustine can be mowed at a height of 3 inches.
- Avoid excessive fertilization because this can increase disease problems. Grass growing in the shade requires less fertilizer because it grows less vigorously.
If after these efforts you still can’t get grass to grow under your tree, we recommend planting the swale with shade-loving plants as mentioned Option 2 & 3. You can refer to this on the Swale Package where you will with the respective forms you need to fill out to get your permit approved.
The most important thing to remember when creating landscaped areas under a tree is to respect the root system of the tree itself. Avoid severing any roots larger than 1 inch in diameter.
If you need to bring in extra soil to create the bed, use as little as possible – preferably no more than 2 to 4 inches. Especially when getting closer to the base of the trunk of the tree because this can lead to decay. If you intend to fill over an area that will cover a large part of the tree’s root system (which extends out well beyond the reach of the branches), do not apply more than 2 inches of soil.