This name is a synonym of Helianthus debilis subsp. tardiflorus Heiser.
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 9EF0D9E9-5816-4052-8A3B-30628043DC3A) with original publication details: 223 1977.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:119099-2.
This name was in version 1 of The Plant List, record gcc-26163, and has not been changed.