I think some of the older cultivars have smaller, less-pollen filled, lighter anthers. At least, that's what I was assuming, but I'm a new hybridizer, too! Off of the top of my head, I think the ones that have the smaller anthers/less pollen in my garden are Saint Elmo's Fire, "Red Challenge" (an old NOID), Starman's Quest, Black Plush, and Night Embers, and maybe one or two others. Considering what is currently producing seed pods though, maybe the 'poor pollinator' theory is more accurate.
I would say my most difficult pollinator, though, is Jim's Pick and a seedling that I had, both of which have large, fluffy pollen heads, which doesn't fall in line with the aforementioned theory.
