That is what I thought as well, from the basic genetics that I learned through hybridising daylilies. With them, you cannot really cross a tetraploid and a diploid, unless you get really, really lucky and get an unreduced gamete in the diploid. However, when I looked into the breeding program of EYOF, it seems that they used 4N (tetraploid) parents quite a lot. The results of 4N x 2N crosses were 3N (triploid) - I can't say I understand how that works. If anyone knows, please enlighten me! I do remember reading that the resultant 3N offspring were infertile, though. (i.e. 'mules' as Eric alludes to above)