Cercis canadensis var. texensis 'Oklahoma' (Oklahoma Redbud)
As the common name implies, it's better adapted to heat and drought, and is a little smaller in mature stature. Bright pink-red flowers. The leaves are rounded and attractively shiny.
Diane has the reddest flowers of the group, with an infusion of copper. They are faintly fragrant. The fall color ranges from non-existent through gold and red.
