As this is a parasitic species, all flower visits will be for nectar only.
Westrich (1989) lists the following as nectar sources: Taraxacum officinale, Cirsium, Carduus, Onopordum, Centaurea (Asteraceae); Knautia arvensis and Scabiosa (Dipsacaceae).
Celary (1989) lists Carduus sp., and Cirsium sp. (Asteraceae) as nectar sources in Poland.