This odd daffodil did not appeal to me when I first saw it, but I find it growing on me in its intriguing and understated way, even if it is no good for the early flying bees. It is one of the oldest selected forms of daffodil in cultivation having arisen (or at least coming into circulation in England) in the 1620's. The relationship to Wild Daffodil is widely quoted but not always obvious in the flower colouration, it would be interesting to know if there is any molecular evidence that conclusively proves the relationship to this species. It certainly merits recording even if the parentage is not known with 100% confidence.
It is reputed to be highly variable in flower form,being strongly influenced by the environment and also with potential to vary from year to year. All the forms I have found, including those I revisit annually, seem reasonably consistent with a well defined perianth whorl and an amazingly convoluted corona, although as can be seen in the following photo the corona does sometimes burst at the seams (perhaps as the flower matures). Given the age of the cultivar, perhaps there is more than one strain in circulation and perhaps some are more consistent than others. Certainly there is evidence of this in the historic literature, and it might be better to treat it as a cultivar group rather than a single cultivar. In 1907 A.M. Kirby wrote in Daffodils, Narcissus and How to Grow Them 'Years ago when there was less demand for Double Van Sion, the growers of flowering bulbs propagated and disseminated their own types of ‘pedigree’ strains, and there was much rivalry among the growers as to the merits of their respective stocks, some having ‘rogued’ to the unburst double trumpet type, others to the ‘rose double’ form, i.e. trumpet burst, its petals curving backwards and intermingling with the perianth segments. Between these two extremes were several intermediate forms.' There is also evidence that it exists in diploid and tetraploid strains, which may add to the variation.
It seems to be confused in certain corners of the internet with the (perhaps justifiably) rare double-flowered form of Tenby Daffodil (Narcissus obvallaris 'Thomas Virescent' (Derwydd Daffodil)) which is sketched and described in BSBI Welsh Bulletin 56. This strikes me as a very ugly daffodil, of which the Pacific Bulb Society photo seems credible (based on the description in the Bulletin) and reminiscent of the 'bunches of green bananas' description, and nothing like the various photos floating around elsewhere on the internet that look much closer to the far more appealing f. pleniflorus.