Ask Mr. Smarty Plants

Mr Smarty Plants tends to agree with you.  I would treat your steep bank, covered with good new soil as a challenge where you should lay some erosion control plantings, then mix in with that a scattering of attractive plants so that you can have some flowers for visual interest.

 With the problem split up in that way, you can first make a plan to control erosion in the slope.  Although solid turf will work, we're all about using natives and its unlikely you will find those as commercial turf.   As a general approach to finding those natives, the best plants to stabilize a slope and prevent erosion are plants like grasses that have fibrous root systems and shrubs and perennials that spread with runners to form thickets.  Here are a set of question/answers that Mr Smarty Plants has already put out for areas near to yours with suggestions as to good approaches:

Native ground covers for rocky, shady slope in Arlington, TX
Plants to stop erosion on sandy slope in north central Texas
Shade tolerant groundcover plants for Tarrant County, Texas
Erosion control plants for Burleson TX

With a general planting of those grasses or groundcovers to stabilize the slope, you can then consider choices of perennials that have a long blooming season and fit with your general scheme.  For this, I used the Recommended Species for North-Central Texas and then searched for Shrubs then Herbs that are perennial and prefer shade to semi-shade.  They don’t have a sort for “flowers the longest”, but I have arranged these in order of the longest blooming season! 

Perennial Shrubs, shade or semi-shade:   Hibiscus laevis (Halberdleaf rosemallow), Anisacanthus quadrifidus var. wrightii (Flame acanthus), Cephalanthus occidentalis (Common buttonbush), Salvia regla (Mountain sage)

Perennial Herbs, shade or semi-shade: Glandularia bipinnatifida var. bipinnatifida (Prairie verbena),  Melampodium leucanthum (Blackfoot daisy), Wedelia texana (Zexmenia), Aquilegia canadensis (Eastern red columbine),  Echinacea purpurea (Eastern purple coneflower), Lobelia cardinalis (Cardinal flower), Salvia roemeriana (Cedar sage), Asclepias tuberosa (Butterflyweed), Conoclinium coelestinum (Blue mistflower), Cooperia drummondii (Evening rain lily)