Jobson and Baleeiro’s 2020 study of Utricularia dichotoma identified 8 closely related but distinct subspecies which together form the species complex. One of these is U. dichotoma subsp. aquilonia, which is named for its northerly distribution relative to other subspecies. I’ve observed this taxon in Blackheath, where it grows in some of the watercourses in the plateaus of the Blue Mountains.
Amongst the species complex, the bracts are an important feature in distinguishing the subspecies. The bracts of U. dichotoma are all attached at the base of the structure, but differ in the shape of the appendages below and at the point of attachment. The upper bract appendage of subsp. aquilonia is moderately wide, rather long and triangular in shape, terminating with an acute point. At the base, the bract is very obviously gibbous (bulging) but a distinct downwards pointing spur is absent.
The subspecies grows long flower stalks up to around 50 cm in length. The leaves have a single central vein, are short and stubby with a rounded edge. The subspecies is terrestrial, occuring in the waterlogged substrates at the banks of shallow permanent creeks. It mainly grows in elevated creeks of the Great Dividing Range from around west of Sydney up to the border with QLD. Near the border, it is also found in heathland swamps.
As with the other members of the complex, the flowers are purple, with a flaring, skirted lower corolla lip and small upper corolla lip. The palate has a set of two or three yellow ridges. In practice, most subspecies of U. dichotoma are very similar and extremely difficult to distinguish without information of the locality and niche.