Quick answer: 18 native Maine plants have a recorded bloom range that includes September.
18 species
- Black-eyed Susan Rudbeckia hirta · 42 states
- Blue mistflower Conoclinium coelestinum · 26 states
- Butterflyweed Asclepias tuberosa · 37 states
- Cardinal flower Lobelia cardinalis · 37 states
- Common yarrow Achillea millefolium · 31 states
- Cutleaf coneflower Rudbeckia laciniata · 21 states
- Fireweed Chamerion angustifolium · 28 states
- Great blue lobelia Lobelia siphilitica · 32 states
- Harebell Campanula rotundifolia · 25 states
- Jerusalem artichoke Helianthus tuberosus · 9 states
- New England aster Symphyotrichum novae-angliae · 18 states
- Partridgeberry Mitchella repens · 17 states
- Pearly everlasting Anaphalis margaritacea · 18 states
- Scarlet beebalm Monarda didyma · 18 states
- Showy tick trefoil Desmodium canadense · 21 states
- Sweet Joe-Pye Eutrochium purpureum · 17 states
- Trumpet vine Campsis radicans · 24 states
- Witch-hazel Hamamelis virginiana · 28 states