Most trees with petaled flowers, like crabapple and redbud, finish blooming in May. We have three trees in bloom now that do have petals. These are catalpa, linden and Japanese tree lilac.
First I’ll explain what I mean by petaled flowers. Not all flowers have petals. They have other flower parts, but no petals. Trees whose flowers have no petals are wind pollinated and do not need to attract pollinators.