Types of tree BMPs

Many different types of tree BMP’s exist. The most prevalent types are described below.

Tree preservation

Where existing trees exist, tree preservation is highly recommended, as existing trees are typically bigger than newly planted trees, and bigger trees provide significantly more benefits than smaller trees.

Incorporating trees into traditional bioretention practices

Incorporating Trees into Traditional Bioretention Practices is also highly recommended.

Accordingly, North Carolina’s bioretention standards recommend incorporating trees in all bioretention practices except for grassed cells: “A minimum of one (1) tree, three (3) shrubs, and three (3) herbaceous species should be incorporated in the bioretention planting plan unless it is a grassed cell. A diverse plant community is necessary to avoid susceptibility to insects and disease.”

Techniques for providing uncompacted soil volume for tree growth and stormwater management under paved surfaces

Where there is not enough open space for traditional bioretention, several techniques exist to protect soil volume under pavement from traffic compaction so that this soil can be used both for bioretention and tree root growth. Examples of these techniques include:

• structural cells
• rock based structural soil
• sand based structural soil
• soil boxes