macrocarpa, while the uncertain consequence of the ploidy status of some or all Black Bullace is absent from research that has focused on crosses of Blackthorn with Damson.

The Damson is a hexaploid grouped with the genetically uncategorised Black Bullace under the same subspecies category, presently as Prunus x domestica subsp.

[8][9] Woldring in his 1998 study noted at least 33 very diverse forms from trailing hedges to large thorny shrubs or even larger plum sized trees over 20 feet in height but bearing mostly Blackthorn characteristics and a confusing absence of dominant intermediary features.

These Woldring grouped under the intermediate forms, as Prunus x fruticans or in some cases more complex back crosses with Blackthorn or Damson, but with little reference to Bullace as a distinct contributor instead of the umbrella term 'Damson' (both lumped as insititia).

[10] As such, without more precise genetic analysis, the forms of hybrid commonly grouped as Prunus x fruticans are very diverse in morphology and represent an unknown affinity to their parent species or varieties of the same, especially due to repeat hybridisation.