Quick answer: 58 native Oklahoma plants have a recorded bloom range that includes May.
58 species
- Birdfoot violet Viola pedata · 14 states
- Black oak Quercus velutina · 2 states
- Black walnut Juglans nigra · 33 states
- Blackjack oak Quercus marilandica · 3 states
- Blue wild indigo Baptisia australis · 6 states
- Buffalograss Bouteloua dactyloides · 9 states
- Bur oak Quercus macrocarpa · 24 states
- Butterflyweed Asclepias tuberosa · 37 states
- Canada wild rye Elymus canadensis · 18 states
- Cardinal flower Lobelia cardinalis · 37 states
- Chinkapin oak Quercus muehlenbergii · 14 states
- Clasping coneflower Dracopis amplexicaulis · 2 states
- Common blue violet Viola sororia · 21 states
- Common hoptree Ptelea trifoliata · 12 states
- Common persimmon Diospyros virginiana · 17 states
- Common selfheal Prunella vulgaris · 2 states
- Common yarrow Achillea millefolium · 31 states
- Downy serviceberry Amelanchier arborea · 34 states
- Dwarf crested iris Iris cristata · 1 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
- Fire pink Silene virginica · 8 states
- Fringed bluestar Amsonia ciliata · 2 states
- Green ash Fraxinus pennsylvanica · 23 states
- Honey locust Gleditsia triacanthos · 9 states
- Indian blanket Gaillardia pulchella · 18 states
- Lanceleaf coreopsis Coreopsis lanceolata · 28 states
- Large penstemon (shell-leaf beardtongue) Penstemon grandiflorus · 8 states
- Largeflower tickseed Coreopsis grandiflora · 2 states
- Lemon beebalm Monarda citriodora · 15 states
- Mexican hat Ratibida columnifera · 17 states
- Narrow-leaf coneflower Echinacea angustifolia · 9 states
- Ohio buckeye Aesculus glabra · 12 states
- Pincushion daisy (perfumeballs) Gaillardia suavis · 1 states
- Pink evening primrose Oenothera speciosa · 8 states
- Plains coreopsis Coreopsis tinctoria · 16 states
- Possumhaw Ilex decidua · 7 states
- Post oak Quercus stellata · 9 states
- Rocky Mountain bee plant Peritoma serrulata · 22 states
- Rough coneflower Rudbeckia grandiflora · 1 states
- Roughleaf dogwood Cornus drummondii · 3 states
- Rusty blackhaw viburnum Viburnum rufidulum · 12 states
- Sassafras Sassafras albidum · 22 states
- Scarlet sage Salvia coccinea · 3 states
- Smooth sumac Rhus glabra · 34 states
- Spotted beebalm Monarda punctata · 14 states
- Standing cypress Ipomopsis rubra · 6 states
- Stiff greenthread Thelesperma filifolium · 1 states
- Sugar maple Acer saccharum · 28 states
- Texas bluebonnet (state flower) Lupinus texensis · 2 states
- Texas star (prairie rose-gentian) Sabatia campestris · 1 states
- Three-flower melic grass Melica nitens · 1 states
- White ash Fraxinus americana · 31 states
- Wild blue Phlox divaricata · 32 states
- Wild hyacinth (Atlantic camas) Camassia scilloides · 1 states
- Winecup Callirhoe involucrata · 7 states