This name is a synonym of Helianthus diffusus Sims.
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 830533CD-B893-4265-8CCD-C7FB936FABD4).
This name record (from TICA) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Helianthus diffusus in version 1 of The Plant List.