Phelipanche nana vs ramosa vs mutelii

Distinguishing Phelipanche nana from P. ramosa and P. mutelii is surely often challenging and they have been sometimes misidentified.
In particular, many observations of P. ramosa from North America seem to be more fitting with P. nana.

This is a key that could turn out to be useful for the users:

  1. Corolla upper outline not or only slightly gibbous (lower and upper outlines nearly parallel towards corolla gorge). Flowers erecto-patent: P. mutelii.

1a) Corolla upper outline distinctly gibbous. Flowers erecto-patent or spreading: 2.

  1. Calyx teeth as long as or shorter than calyx tube, narrowly triangular. Flowers erecto-patent. Stem often branched. Corolla light blue to whitish. Parasitizing cultivated plants: P. ramosa.

2a) Calyx teeth longer than calyx tube, subulate. Flowers spreading. Stem rarely branched. Corolla blue, rarely light blue or whitish. Parasitizing wild plants: P. nana.

N.B. in order to observe the “calyx teeth” character, it would be useful to detach the flower from the inflorescence, to remove the bract and to photograph the calyx with a macro lens or under a stereomicroscope.

Sources:

Originalli posted here:
https://www.inaturalist.org/journal/blue_celery/23520-phelipanche-nana-vs-ramosa-vs-mutelii

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