My guess is no, though I can't back that up with anything authoritative -- just that I have never heard of an I. opaca x aquifolium cross. Out of curiosity, do you already have the female American holly? Or is it a purchase you're considering? I hear I. opaca is great for salt spray sites.

I looked at Ilex opaca (and especially I. verticillata) for a while but concluded that I just don't have space for it -- especially two of them -- in my current yard.

Just bought an American Holly. Have had a couple Blue Prince and and English Holly for years. American Holly is a tree I've lusted after for years but had trouble getting established. This time I spent more for a larger specimen. I love large, tree form holly. There is a breathtaking grove of them in a small woods nearby.

Sounds beautiful. I see evergreen hollies a lot around Kansas City
but to me they look out of place here, especially in the dry dead of a
windy, snowless winter. Poor things really seem to suffer.

My
uncle had one next to his house in a town in the Pennsylvania mountains.
He kept it trimmed into a perfect Christmas tree shape and he and my
aunt spent quite a lot decorating it in a completely different fashion
every year. My dad loved that kind of thing but there was no way it was
going to work out in the Kansas Flint Hills.I like berries, just not on my sidewalks. I've planted viburnums, spicebushes, a serviceberry and a green hawthorn. I would love to have an annual visit from cedar waxwings, always one of my favorite birds.

Gardengal48, one of the things I miss most about living in the PNW is eating fresh blackberries and the various hybrids between them and raspberries. I haven't had a good berry in years.

Yes, we do grow some sensational berries here - strawberries (local ones just starting) raspberries, blueberries, huckleberries and blackberries. Unfortunately, the best tasting blackberries are of the Himalayan persuasion and these are a major invasive species in this area. The large, juicy and absolutely delicious late summer berries are their only saving grace.

btw, English holly is a pretty significant invasive problem in this area. While not yet officially declared, it is on the "watch list" for both WA and OR. It pops up all over the place in my pretty rural native, woodsy area, thanks to the birds.

I like tree form hollies, American and English. In a grove in the forest where they lose their lower branches, the old American Holly reveal a smooth, beech like bark. American holly are one of the few native broadleaf evergreen trees in my zone and are somewhat salt tolerant, making them useful in coastal windbreaks or privacy screens by roads. They are the Queens of winter interest, with both evergreen foliage and red berries.

Despite what the listed zonal tolerance is, I think I'm at the effective edge of the range of American Holly. I don't doubt there are holly in Zone 5, but I suspect they are in sheltered micro climates English holly doesn't do well here...it sort of limps along. The Meserve/Blue Hollies do great, but I'm not as excited by small hollies.

English Holly isn't listed as invasive here. I was a bit worried about polluting the local gene pool or having hybrids become invasive. My plan was to plant this one female ilex opaca, see how it goes, and if it does well by more next year (including a male). Depending on my answers to the above questions, I could move some of my hollies or go ahead and buy a male American Holly now.

This is Off topic. @ woodstea. Your mention of loving cedar wax wings and not liking berries on the sidewalk made me laugh since cedar waxwings make a appearance down here in huge undulating flocks in late winter that strip any berry off any tree and leave a dearth of poo on the sidewalk. Life is full of choices. LOL. They are individually pretty birds, but they and the grackles always make me feel like I am in a certain Alfred Hitchcock Movie. These bandits look a little like Trump.

Heh heh, I suppose I like cedar waxwings so much because I almost never see them. Your description reminds me of how I feel about Canada Geese.

I keep thinking I want to attract more wildlife to my yard, but I don't always like the wildlife that shows up. I'm sick of the rabbits and their recent offspring, and the squirrels, and the house sparrows that built a nest right above my back door.

It makes me think that outdoor cats aren't such a bad idea.