Branched Bur-reed Sparganium erectum can only be identified to subspecies from ripe brown fruit, which do not mature until late in the season. They are best collected when the fruits are just starting to turn brown and are coming away from the fruiting head. The fruits can then be left to mature on a sunny windowsill as they need to be brown and fully mature as shown in the picture above to be able to confidently distinguish the different subspecies.

Sparganium erectum ssp. neglectum was found in a ditch on Marston Marshes. The fruits are light brown, ellipsoidal and gradually taper below the beak.

Sparganium erectum ssp. microcarpum was found on the banks of the River Bure to the west of Wroxham. The fruits are dark brown and narrow abruptly below the beak and need to be distinguished from the much flatter fruits of ssp. erectum, which is also found by the River Bure.