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) and Scabiosa (Dipsacaceae).
Celary (1989) lists the following nectar sources in Poland: Calluna vulgaris (Ericaceae); Carduus sp., Cirsium lanceolatum, Cirsium arvense, Centaurea scabiosa, Centaurea rhenana, Centaurea jacea, Taraxacum officinale (Asteraceae)
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Ornosa & Ortiz-Sánchez (2004) list the following families of plants as providing nectar: Fabaceae, Asteraceae and Dipsacaceae.