Ask Mr. Smarty Plants

Cephalanthus occidentalis (Common buttonbush) would be an excellent choice for the creekside.  It is frequently found along streams and does well in shade and part shade and is native to Nacogdoches County.

Here are some other plants that would fit your criteria that are also native to Nacogdoches County:

Shrubs:

Aesculus pavia (Scarlet buckeye) is another shrub that likes moist soil and grows in part shade.

Callicarpa americana (American beautyberry) thrives in moist soils and part shade.   It is valuable as a wildlife food plant.

Euonymus americanus (American strawberry-bush) does well in part shade and moist soils.

Itea virginica (Virginia sweetspire) an understory shrub that grows well in part shade, moist soil and is noted for its erosion control capabilities.

Grasses:  Grasses have extensive fibrous roots that hold the soil well.

Chasmanthium latifolium (Inland sea oats) is a beautiful grass that likes wet soils and thrives in the shade and part shade. 

Andropogon glomeratus (Bushy bluestem) is an attractive grass that also loves moist soils, but it needs full sun to thrive.

Ferns:  Ferns do well in shade and part shade in moist soils.

Athyrium filix-femina (Common ladyfern) is a large fern, growing to 2-3 feet high.

Pteridium aquilinum (Western bracken fern) is also a large fern and grows in dry soils as well as wet soils in shade and part shade.

Herbs:

Conoclinium coelestinum (Blue mistflower) grows in sun and part shade and attracts butterflies.

Salvia lyrata (Lyreleaf sage) is evergreen, grows in sun, part shade and shade and tolerates flooding.

Teucrium canadense (Canada germander) grows in moist soils in part shade and near streams.