Quick answer: 29 native Utah plants have a recorded bloom range that includes May.
29 species
- Alderleaf mountain mahogany Cercocarpus montanus · 9 states
- Apache plume Fallugia paradoxa · 6 states
- Banana yucca Yucca baccata · 6 states
- Bearberry Arctostaphylos uva-ursi · 16 states
- Bog laurel Kalmia polifolia · 5 states
- Butterflyweed Asclepias tuberosa · 37 states
- Canada wild rye Elymus canadensis · 18 states
- Chokecherry Prunus virginiana · 35 states
- Creeping Oregon grape Mahonia repens · 11 states
- Creosote bush Larrea tridentata · 5 states
- Downy serviceberry Amelanchier arborea · 34 states
- Gambel oak Quercus gambelii · 6 states
- Golden currant Ribes aureum · 3 states
- Gray alder Alnus incana · 12 states
- Old man's whiskers Geum triflorum · 8 states
- Prairie Junegrass Koeleria macrantha · 15 states
- Quaking aspen Populus tremuloides · 24 states
- Red-osier dogwood Cornus sericea · 22 states
- Rocky Mountain bee plant Peritoma serrulata · 22 states
- Rocky Mountain iris Iris missouriensis · 7 states
- Rocky Mountain penstemon Penstemon strictus · 4 states
- Scarlet globemallow Sphaeralcea coccinea · 5 states
- Silver buffaloberry Shepherdia argentea · 11 states
- Smooth sumac Rhus glabra · 34 states
- Utah serviceberry Amelanchier utahensis · 3 states
- Utah sweetvetch Hedysarum boreale · 3 states
- Wax currant Ribes cereum · 2 states
- Winecup Callirhoe involucrata · 7 states
- Wyoming Indian paintbrush Castilleja linariifolia · 4 states