> Gernot Katzer, the Austrian with the Spice Pages, plumps for
_Tridax_.
> I can't find much on-line for plants of that genus apart from their
> potential as invasive weeds.

Actually, the idea with Tridax coronpiifolia also stems from Diana
Kennedy (in "From My Mexican Kitchen: Techniques and Ingredients").
There, she gives a photo of the plant: It looks similar to a
dandelion, with tiny, slim leaves. Moreover, there is a flower
haed which clearly marks the plant as a member of the Asteraceae
family. It looks somewhat similar to the plant shown in
http://www.classicpix.com/cat/psdbi/...am1=058703677X ,
but the leaves are more serrated, and the flower head is closed
so that I cannot guess its size nore color.

In contrast, Castilleja lanata is a member of the Scrophulariaceae
family that looks totally different.
http://www-plb.ucdavis.edu/botanyclu...a%20lanata.jpg

Kennedy describes the flavour of hierba de conejo as "waxy but
pleasant", which seems pretty oxymoric to me. I have never seen
the plant, as the finer points of Mexican food are pretty outside
the general scope here in Europe.