Carolina Larkspur (Delphinum carolinium) - 4' tall.
Blooms May - July.  These spurred flowers may be deep blue, reddish - blue, or white.  Native perennial.  OZ, OU, CP.

Mexican Hat  (Ratibida columnifera) ― 2 - 3' tall.
Blooms June - October.  A widely planted form of a native perennial.  Statewide.

Queen Ann's Lace (Daucus carota)  ― 1 - 4' tall

Blooms May - frost.  This is the ancestor of the cultivated carrot.  Introduced biennial. Statewide.

Black-eyed Susan  (Rudbeckia hirta) ― 2 - 3' tall with one 2" flower head on each hairy stem.

Blooms May - October.  Native Biennial or short-lived perennial.  Statewide.

Showy Evening Primrose  (Oenothera speciosa) ― 1 - 2' tall.

Blooms April - July.  White or pink flowers.  Native perennial.  Statewide.

Pale Purple Coneflower (Echinacea pallida) - 3' tall.

Blooms May - July.  Native perennial.  OZ, OU, CP.

Lance-leaved Coreopsis (Coreopsis lanceolata) - 3' tall.

Blooms April - June.  Native perennial.  Statewide.

Chicory  (Coreopsis intybus) - 4' tall.

Blooms May - October.  

This European native's roots are sometimes used as a coffee substitute or additive.  Perennial.  OZ, OU.

Rough Blazing Star  (Liatrus aspera)  ― 3 - 4' tall.
Blooms July - October.  The unopened flower buds resemble small cabbages.  Native perennial.  Statewide.

Cardinal Flower (Lobelia cardinalis) - 3' tall.
Blooms August - October. This flower attracts hummingbirds.  Native perennial. Statewide. 

Arkansas Beard Tongue (Penstemon arkansanus) - Less than 2' tall.
Blooms April - June.  The 3/4" whitish flowers have lavender streaking.  Native perennial. OZ, OU.

Purple Coneflower  (Echinacea purpurea) - Up to 4' tall. 
Blooms from June - October.  
The ray flowers are more purple than those of pale purple coneflower. Native perennial. OZ, OU.

Downy Phlox (Phlox pilosa) - 2' tall.

Blooms April - July.  

Flowers can be pink, pale pink, or sometimes white with purple centers.  Native perennial.  OZ, OU, CP.

Spider Lily (Hymenocallis caroliniana) - 3' tall.

Blooms May - August.  These large white flowers have a distinctive spider-like shape. Native perennial. OU, GP, AP.

Rose Vervain (Glandularia canadensis) - Plants less than 2' tall.

Blooms March - September.  The source of many garden hybrids.  Native perennial.  OZ, OU, CP, AP.

Indian Paintbrush (Castilleja coccinea) ― 1 - 2' tall.  The bracts that surround the small flowers displays brilliant colors.

Blooms April - June.  Native annual.  Found on prairies in the OZ, CP, AP.

Wild (Monarda fistulosa) ― 2 - 4' tall.
Blooms June - September.  Also called Bee Balm.  Flowers pinkish, lavender, or lilac.  Statewide.

Goldenrod (Solidago canadensis) ― 4 - 6' tall.

Blooms July - September.  Native perennial.  Statewide.

Ohio Spiderwort (Tradescantia ohiensis) - Stems 3' tall.
Blooms May - July.
So named because the internal jellylike substance resembles a spider's web.  Native perennial.  OZ, OU, CP.

Plains Coreopsis (Coreopsis tinctoria) - 3' tall.

Blooms June - September.  Native annual.  Statewide.

Bird's Foot Violet (Viola pedata) - 6" tall.

Blooms April - May.  This violet occurs in several different colors:  light violet, dark violet, or dark violet with 2 dark purple petals. Native perennial.  OZ, OU, CP.

Butterfly Weed (Asclepias tuberosa) ― 1 - 2' tall.

Blooms May - September.  Flower's nectar attractive to butterflies.  Native perennial.  Statewide.

Ox-eyed Daisy (Chrysanthemum leucanthemum) - 2" flower heads.

Blooms May - July.  Introduced perennial.  OZ, OU, CP.

Tickseed (Bidens aristosa) ― 1 - 6' tall.

Blooms August - November.  This late bloomer is often found in large stands.  Native perennial.  Statewide.