Quick answer: 94 native Ohio plants have a recorded bloom range that includes May.
94 species
- Allegheny serviceberry Amelanchier laevis · 1 states
- American basswood Tilia americana · 32 states
- American beech Fagus grandifolia · 24 states
- American bladdernut Staphylea trifolia · 15 states
- American hazelnut Corylus americana · 16 states
- American holly Ilex opaca · 24 states
- American hornbeam Carpinus caroliniana · 29 states
- American mountain ash Sorbus americana · 18 states
- American plum Prunus americana · 25 states
- Bebb willow Salix bebbiana · 2 states
- Black cherry Prunus serotina · 32 states
- Black locust Robinia pseudoacacia · 12 states
- Black maple Acer nigrum · 3 states
- Black walnut Juglans nigra · 33 states
- Black willow Salix nigra · 2 states
- Blackhaw Viburnum prunifolium · 12 states
- Bog birch Betula pumila · 1 states
- Bur oak Quercus macrocarpa · 24 states
- Butterflyweed Asclepias tuberosa · 37 states
- Butternut Juglans cinerea · 5 states
- Canada anemone Anemone canadensis · 22 states
- Canada plum Prunus nigra · 2 states
- Canada wild rye Elymus canadensis · 18 states
- Canada yew Taxus canadensis · 4 states
- Canadian serviceberry Amelanchier canadensis · 17 states
- Cardinal flower Lobelia cardinalis · 37 states
- Carolina springbeauty Claytonia caroliniana · 8 states
- Chinkapin oak Quercus muehlenbergii · 14 states
- Chokecherry Prunus virginiana · 35 states
- Common elderberry Sambucus nigra ssp. canadensis · 16 states
- Common hoptree Ptelea trifoliata · 12 states
- Common ninebark Physocarpus opulifolius · 22 states
- Common persimmon Diospyros virginiana · 17 states
- Common winterberry Ilex verticillata · 10 states
- Common yarrow Achillea millefolium · 31 states
- Coralberry Symphoricarpos orbiculatus · 20 states
- Creeping phlox Phlox subulata · 11 states
- Creeping phlox Phlox stolonifera · 2 states
- Cucumbertree Magnolia acuminata · 12 states
- Downy serviceberry Amelanchier arborea · 34 states
- Dwarf fothergilla Fothergilla gardenii · 9 states
- Dwarf larkspur Delphinium tricorne · 2 states
- Eastern hop-hornbeam Ostrya virginiana · 18 states
- Eastern purple coneflower Echinacea purpurea · 22 states
- Eastern red cedar Juniperus virginiana · 36 states
- Eastern red columbine Aquilegia canadensis · 36 states
- Eastern redbud Cercis canadensis · 30 states
- Eastern wahoo Euonymus atropurpureus · 2 states
- Flowering dogwood Cornus florida · 22 states
- Foxglove beardtongue Penstemon digitalis · 31 states
- Fragrant sumac Rhus aromatica · 14 states
- Honey locust Gleditsia triacanthos · 9 states
- Indigo bush Amorpha fruticosa · 16 states
- Jacob's ladder Polemonium reptans · 17 states
- Lanceleaf coreopsis Coreopsis lanceolata · 28 states
- Mapleleaf viburnum Viburnum acerifolium · 5 states
- Nannyberry Viburnum lentago · 23 states
- New Jersey tea Ceanothus americanus · 31 states
- Northern red oak Quercus rubra · 24 states
- Ohio buckeye Aesculus glabra · 12 states
- Pagoda dogwood Cornus alternifolia · 25 states
- Partridgeberry Mitchella repens · 17 states
- Pawpaw Asimina triloba · 17 states
- Peachleaf willow Salix amygdaloides · 3 states
- Pin cherry Prunus pensylvanica · 3 states
- Pin oak Quercus palustris · 18 states
- Porcupine grass Hesperostipa spartea · 2 states
- Prairie Junegrass Koeleria macrantha · 15 states
- Quaking aspen Populus tremuloides · 24 states
- Red baneberry Actaea rubra · 22 states
- Red-osier dogwood Cornus sericea · 22 states
- Rocky Mountain bee plant Peritoma serrulata · 22 states
- Rusty blackhaw viburnum Viburnum rufidulum · 12 states
- Sand cherry Prunus pumila · 1 states
- Sassafras Sassafras albidum · 22 states
- Scarlet beebalm Monarda didyma · 18 states
- Scarlet oak Quercus coccinea · 17 states
- Shagbark hickory Carya ovata · 22 states
- Smooth sumac Rhus glabra · 34 states
- Sourwood Oxydendrum arboreum · 14 states
- Sugar maple Acer saccharum · 28 states
- Sundial lupine Lupinus perennis · 25 states
- Swamp rose Rosa palustris · 11 states
- Swamp white oak Quercus bicolor · 9 states
- Sweet birch Betula lenta · 18 states
- Sweet crabapple Malus coronaria · 5 states
- Sweetgum Liquidambar styraciflua · 22 states
- Tulip tree Liriodendron tulipifera · 17 states
- Virginia creeper Parthenocissus quinquefolia · 27 states
- Virginia springbeauty Claytonia virginica · 10 states
- White ash Fraxinus americana · 31 states
- White baneberry Actaea pachypoda · 16 states
- White oak Quercus alba · 33 states
- Wild blue Phlox divaricata · 32 states