One bush with nearly all trifoliate leaves has repeatedly developed an extra leaf pair, at times virtually merged with the node of the topmost leaflets.
This formation, unique among hundreds of bushes surveyed, would appear to reflect introgressive hybridization resulting in an almost total B. trifoliolata gene pool, additionally supporated by its 4-5-spinose leaflet margins. But this bush otherwise lacked phenological and morphological indicators of hybridization, such as dentate filaments.
