60 wildflowers were recorded blooming in Missouri in September in our iNaturalist sample; 22 of the top 50 are at their peak this month. The list is ranked by number of research-grade observations.
Top wildflowers in September

White Snakeroot

Great Blue Lobelia

Asiatic dayflower
Wingstem

American hog-peanut

brown-eyed Susan

Purple Passionflower

Common Jewelweed

Blue Mistflower
White Morning-glory
Cardinal Flower

Common Morning-Glory
All wildflowers blooming in Missouri in September
| # | Species | Scientific name | Family | Obs. | Peak in state |
|---|---|---|---|---|---|
| 1 | White Snakeroot | Ageratina altissima | Sunflowers, Daisies, Asters, and Allies | 99 | Sep (peak) |
| 2 | Great Blue Lobelia | Lobelia siphilitica | bellflower family | 76 | Sep (peak) |
| 3 | Asiatic dayflower | Commelina communis | Spiderworts | 74 | Sep (peak) |
| 4 | Wingstem | Verbesina alternifolia | Sunflowers, Daisies, Asters, and Allies | 67 | Sep (peak) |
| 5 | American hog-peanut | Amphicarpaea bracteata | Legumes | 59 | Aug (past peak) |
| 6 | brown-eyed Susan | Rudbeckia triloba | Sunflowers, Daisies, Asters, and Allies | 56 | Aug (past peak) |
| 7 | Purple Passionflower | Passiflora incarnata | Passionfruit Family | 51 | Aug (past peak) |
| 8 | Common Jewelweed | Impatiens capensis | balsam family | 42 | Sep (peak) |
| 9 | Blue Mistflower | Conoclinium coelestinum | Sunflowers, Daisies, Asters, and Allies | 41 | Sep (peak) |
| 10 | White Morning-glory | Ipomoea lacunosa | bindweed family | 37 | Sep (peak) |
| 11 | Cardinal Flower | Lobelia cardinalis | bellflower family | 33 | Sep (peak) |
| 12 | Common Morning-Glory | Ipomoea purpurea | bindweed family | 32 | Sep (peak) |
| 13 | Late Boneset | Eupatorium serotinum | Sunflowers, Daisies, Asters, and Allies | 25 | Sep (peak) |
| 14 | Frostweed | Verbesina virginica | Sunflowers, Daisies, Asters, and Allies | 25 | Sep (peak) |
| 15 | Common Hibiscus | Hibiscus syriacus | Mallow and Hibiscus Family | 23 | Aug (past peak) |
| 16 | Tall Goldenrod | Solidago altissima | Sunflowers, Daisies, Asters, and Allies | 22 | Sep (peak) |
| 17 | New England aster | Symphyotrichum novae-angliae | Sunflowers, Daisies, Asters, and Allies | 21 | Sep (peak) |
| 18 | Leafy Elephant's-Foot | Elephantopus carolinianus | Sunflowers, Daisies, Asters, and Allies | 19 | Aug (past peak) |
| 19 | Chicory | Cichorium intybus | Sunflowers, Daisies, Asters, and Allies | 18 | Jul (past peak) |
| 20 | Whitemouth Dayflower | Commelina erecta | Spiderworts | 16 | Jul (past peak) |
| 21 | Smooth Hedgenettle | Stachys tenuifolia | Mint Family | 15 | Jul (past peak) |
| 22 | Low Smartweed | Persicaria longiseta | knotweed family | 14 | Sep (peak) |
| 23 | Pale Jewelweed | Impatiens pallida | balsam family | 13 | Sep (peak) |
| 24 | Nodding Beggarticks | Bidens cernua | Sunflowers, Daisies, Asters, and Allies | 13 | Sep (peak) |
| 25 | Tall Bellflower | Campanulastrum americanum | bellflower family | 13 | Jul (past peak) |
| 26 | Carolina horsenettle | Solanum carolinense | nightshade family | 12 | Jun (past peak) |
| 27 | Common Sneezeweed | Helenium autumnale | Sunflowers, Daisies, Asters, and Allies | 12 | Sep (peak) |
| 28 | Fall Phlox | Phlox paniculata | phlox family | 11 | Oct (rising) |
| 29 | Partridge Pea | Chamaecrista fasciculata | Legumes | 10 | Aug (past peak) |
| 30 | Sharpwing Monkeyflower | Mimulus alatus | lopseed family | 10 | Jul (past peak) |
| 31 | Pickerelweed | Pontederia cordata | Pickerelweeds | 9 | Jun (past peak) |
| 32 | Field Bindweed | Convolvulus arvensis | bindweed family | 9 | Jun (past peak) |
| 33 | Giant Ragweed | Ambrosia trifida | Sunflowers, Daisies, Asters, and Allies | 9 | Aug (past peak) |
| 34 | Field Thistle | Cirsium discolor | Sunflowers, Daisies, Asters, and Allies | 9 | Sep (peak) |
| 35 | Frost Aster | Symphyotrichum pilosum | Sunflowers, Daisies, Asters, and Allies | 9 | Sep (peak) |
| 36 | American jumpseed | Persicaria virginiana | knotweed family | 9 | Aug (past peak) |
| 37 | Lanceleaf Frogfruit | Phyla lanceolata | Verbena Family | 8 | Aug (past peak) |
| 38 | Autumn Clematis | Clematis terniflora | buttercup family | 8 | Aug (past peak) |
| 39 | Obedient Plant | Physostegia virginiana | Mint Family | 8 | Aug (past peak) |
| 40 | Blue Curls | Trichostema dichotomum | Mint Family | 8 | Sep (peak) |
| 41 | Trailing Fuzzy-Bean | Strophostyles helvola | Legumes | 8 | Aug (past peak) |
| 42 | American pokeweed | Phytolacca americana | Pokeweed Family | 7 | Jul (past peak) |
| 43 | Red Clover | Trifolium pratense | Legumes | 7 | May (past peak) |
| 44 | Japanese honeysuckle | Lonicera japonica | honeysuckle family | 7 | May (past peak) |
| 45 | Cup Plant | Silphium perfoliatum | Sunflowers, Daisies, Asters, and Allies | 7 | Aug (past peak) |
| 46 | Hairy Ruellia | Ruellia humilis | Acanthus Family | 7 | Jul (past peak) |
| 47 | Swamp Milkweed | Asclepias incarnata | Dogbane Family | 7 | Aug (past peak) |
| 48 | Jimsonweed | Datura stramonium | nightshade family | 6 | Sep (peak) |
| 49 | Flower-Of-An-Hour | Hibiscus trionum | Mallow and Hibiscus Family | 6 | Sep (peak) |
| 50 | American groundnut | Apios americana | Legumes | 6 | Aug (past peak) |