Quick answer: 21 native New Hampshire plants have a recorded bloom range that includes September.
21 species
- Balsam fir Abies balsamea · 2 states
- 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
- 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
- Sensitive fern Onoclea sensibilis · 1 states
- Showy tick trefoil Desmodium canadense · 21 states
- Sweet Joe-Pye Eutrochium purpureum · 17 states
- Trumpet vine Campsis radicans · 24 states
- Virgin's bower Clematis virginiana · 2 states
- Virginia chain fern Woodwardia virginica · 1 states
- Witch-hazel Hamamelis virginiana · 28 states