The planted layers within a landscape include the tree (canopy) and understory layers as well as the ground plane, the most important layer.

在景观的种植层包括树（树冠）和林下层以及地平面上，最重要的一层。

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Now, in many older neighborhoods, the urban forest has matured, making our suburban spaces shadier, and increasingly our garden understory is affected by tree roots.

NPR: Excerpt: 'The American Meadow Garden'