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Silva Cell Alternatives

The need for plants in cities has become increasingly clear as climate change progresses. Cities have air pollution, hotter temperatures, and polluted water. Silva Cells were introduced to deal with soil compaction and stormwater drainage. They are underground structures that keep soil from getting compacted and allow stormwater to drain more freely into the ground. They are not the only technology that exists for improving tree planting in cities, though.

  1. Structural Soil

    • The idea behind structural soil is that load-bearing stones are added to the ground where trees will be planted above. These stones add structure and stability to the ground so that it may be used for human purposes, while avoiding soil compaction. The load-bearing stones are placed together in such a way that there are spaces between each. This aerates the soil by leaving air pockets, which will improve stormwater drainage as well. The roots of trees planted above will also be able to grow through these spaces, allowing trees to grow larger and healthier for a longer period of time. This differs from Silva Cells because the stones are mixed with the soil area, meaning more space is taken up than Silva Cells because of the need for more soil.

    Dual Function Growth Medium

    • Dual function growth medium has been studied by the Environmental Protection Agency, and is shown to create a permeable surface for plants and grasses to grow in parking areas and other areas around cities. A 50-50 mixture of shale and sand, plus the introduction of porous peat moss, can still be used structurally in city planning while allowing for more planting surface that is not affected by soil compaction. It decreases the amount of impermeable surfaces in the city, helping to absorb more water rather than letting it become runoff. It also enables grasses or other plants to grow to help cool the city and filter pollutants from the air and ground. This technique is more for creating porous surfaces than tree planting, while Silva Cells focus more on improved tree planting.

    Bioretention

    • The City of Charlotte, North Carolina, implemented a soil structure similar to Silva Cells. Concrete columns were poured and a sidewalk was built on top, keeping the soil beneath uncompacted. Trees and plants could be planted and have access to the soil beneath the sidewalk. A spillway was implemented, sloping stormwater runoff into the planting area of the structure. This plan is a more complicated structure than Silva Cells and must be custom built for each area that it is used in. Another similar attempt used plastic PVC pipe to create boxes to hold water and soil underground.

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