According to Missouri Botanical Gardens :

"Cercis canadensis var. texensis, synonymous with and formerly known as Cercis reniformis, is a variety of eastern redbud that is native to Oklahoma and Texas."

âÂÂOklahomaâ is even more compact and broad-rounded than Cercis canadensis var. texensis, typically maturing to 12-18â tall. It is more commonly sold in commerce than var. texensis in large part because its flowers are darker (rosy magenta to wine red) and its leaves are a richer green with more gloss and wax. âÂÂOklahomaâ was discovered growing wild in the Arbuckle Mountains of Oklahoma in 1964.

So I think the differing answers you are seeing are a result of the age of the reference material used, reniformis being an older and outdated species name.

A Cercis canadensis var. texensis might be commonly called an Oklahoma Redbud but if you want the cultivar 'Oklahoma' I would buy from a reputable nursery and specify exactly what you want.

Here is a link that might be useful: Cercis canadensis var. texensis 'Oklahoma'

This post was edited by cearbhaill on Tue, Jun 10, 14 at 12:11