Grows well well north of its native range.  Documented in very southern counties with an outlier in Martin County -- that outlier is also unique in that it was collected near a cypress dome. Closely related to corn, this species has been crossed with maize to produce a corn that is resistant to Helminthosporium turcicum, the fungus that causes northern leaf blight  (Wikipedia). Listed as Threatened in Florida. Informal borders.

The author treats this as a friendly weed. Pull them if where there is something more desirable. Back of a wildflower garden in a casual setting. Grown en-masse, this plant can be used as a temporary groundcover.

Informal shady semi-shady gardens.

Rear of garden as a screen.  Native meadows.

Trellis or fence

In a managed garden, gamagrass can be trimmed back at the end of winter. Hedge, foundation planting, individual large grass clump, background screen for a flower garden. Rain garden or bioswale.

The name Walter's viburnum honors Thomas Walter (1740-89), English-born planter of South Carolina, who described this species in his Flora Caroliniana. Specimen plant, hedge or screen plant. Can be allowed to form a thicket, sheared, or kept pruned into a tree.  Fast growing.