'Holden Clough' has been counted as having 2n=37 so the most likely pairing, in my opinion, was I. pseudacorus X I. versicolor and the interior leaf patterns of plants in the Holden Clough line support this.
Regardless, I thought it worth the time to try the cross. One pod from I. versicolor set on one of the last blooms of I. pseudacorus of the season.
Normal I. pseudacorus seeds are shown at the top of the image for comparison.
The resulting seeds were reminiscent of the #1 batch of I. pseudacorus X I. fulva seeds in that they were noticeably smaller and darker in color than normal I. pseudacorus seeds. Of 65 seeds produced, at least 28 appeared viable but none germinated.
A second cross yeilded seeds which looked perfectly pseudacorus. Only 2 germinated in 2002 and only one of these was strong enough to survive transplanting into a seedling bed.
Even as a tiny seedling, the leaves were considerably darker in color than I. pseudacorus.
As a mature plant, it is considerably shorter than the pseudacorus, being a fraction shorter than the versicolor used. The bloom is typically doubled and does not set seed. Rarely though, a single form of the bloom will show itself and I'm hoping that all parts will be normal enough to allow a cross.
