Silva Cell Trees Outperforming Structural Soil in Greenwich Streetscape

Two trees utilizing DeepRoot Silva Cells are flourishing compared to a pair of nearby trees planted in structural soil


In 2015, a mixed-use commercial and residential building was constructed on Greenwich Avenue in the Connecticut town of the same name — a three-story structure known colloquially as the “gateway” to the nominal road for its highly trafficked location. The Victorian-style architecture is complemented by street trees framing the corner of Greenwich Avenue and Railroad Avenue, part of a green infrastructure upgrade initiated by Eric Rains Landscape Architecture. The two trees along Greenwich — provided 1,050 cubic feet of shared soil volume with the DeepRoot Silva Cell system — are thriving, while the two Railroad plantings in structural soil are lagging behind, noticeably lacking in robust growth and canopy fullness.

Installation Summary

Number of Silva Cells: 42 (2X)

Shared Soil Volume: 1,050 ft3

Number of Trees and Type: 2 Silver Linden (Tilia Tomentosa)

Type of Project: Streetscape

Project Designer: Eric Rains Landscape Architecture

Project Contractor: Gateway Development Group

Installation Date of Silva Cells: June 2016

The Project and DeepRoot Silva Cell Success

A Victorian-inspired, three-story structure erected in 2015, the building at 415 Greenwich Avenue serves as the first thing commuters see when coming off the train or I-95. The 14,000 square foot commercial and residential building is flanked by a corner streetscape that simultaneously underwent a facelift project, spearheaded on the Greenwich Avenue side by Eric Rains Landscape Architecture.

With input from the Greenwich Tree Conservancy, a local tree advocacy group, green infrastructure was incorporated into the design plans from the very beginning. Two Silver Linden trees were planted, along the Greenwich Avenue side of the corner façade, with the goal of achieving large canopy coverage as an eye-catching complement to the impressive new building.

A total of 42 (2X) Silva Cells were installed, providing approximately 1,050 cubic feet of soil volume for the newly planted trees. As Eric Rains notes, urban forestry is often a challenging element of any streetscape project — and the DeepRoot Silva Cells helped ensure success: “Street trees are among the most difficult planting scenarios that landscape architects undertake, but when you get it right, the rewards for the effort are very valuable in turns of urban canopy and its co-benefits like urban heat island reduction, carbon sequestration, and especially real estate value enhancement.”

The Progress

Just months after the installation, one of the Silver Linden trees died from transplant shock in what was a severe drought year; luckily, the replacement tree has access to high-quality loamy soils within the Silva Cells to assist in its quick, healthy maturation.

Four years later, both trees are thriving. Their large, shady canopies were instrumental in providing locals with a welcoming respite from the summer heat, particularly during the early days of Covid-19 when the bottom portion of the block was shut down to offer residents an outdoor community gathering space.

A most interesting contrast also presents itself on this corner streetscape: there were two additional trees planted on the Railroad Avenue side of the building façade at the same time, framing the corner with a total of four trees. While the Greenwich Avenue trees were planted in Silva Cells, the Railroad Avenue trees are accessing structural soil.

The results? While the trees planted in Silva Cells are robust and flourishing, their Railroad Avenue counterparts are shorter, thinner, and less full. As JoAnn Messina of the Greenwich Tree Conservancy observed: “The trees on Railroad Avenue didn’t use Silva Cell, just look at the comparison!” The gravel-based structural soil (GBSS) used on Railroad Avenue has a number of disadvantages when compared to the Silva Cell suspended pavement system. The plant response of the trees in the GBSS (CU SoilTM) on Railroad Avenue is typical of rock-based media. Studies have shown that the aggregate mix totaling 80% of the volume provides no value to the trees. Silva Cells, on the other hand, are close to 95% structure providing for much more loamy soils in a smaller area, reducing cost and creating a healthy environment for thriving root expansion. This is yet another example of the growth benefits of Silva Cell-planted trees as opposed to other soil media — for more on this academic research, check out our blog.

Additional Resources

The Greenwich Tree Conservancy has a mission to preserve and enhance the trees of Greenwich, in part by documenting the trees within the town and tracking the performance of various trees throughout the city. They offer educational resources in tree care, advocacy, and getting together for “tree parties.” Learn more about their organization by checking out their website.

Also, check out our nearby project in New London, Connecticut.


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