It it better known as Leucanthemum 'Becky'. It was named after Becky first.
Ryan has one called Chrysanthemum/Dendrobium 'Ryans Pink'.
They keep changing the names.
It's pretty common at Lowes and Home Depot.

Here is a link that might be useful: Becky

Blast--I didn't know Ryan's White is Becky. Someone told me it was a white Clara Curtis (Country Girl). Becky was a dismal failure in my yard, but Clara Curtis is a real winner, and I'm looking for a white that will do as well.

Thanks.

Whiskers, I bought a white chrysanthemum from Stephen F Austin's plant sale. It was highly praised and recommneded but everyone working and shopping that day. I find it is excellent. I don't know the name but I could send you cuttings if your into rooting things. Most mums root easily by sticking thme in the ground.

After looking at page cactusfreak gave a link to, it appears 'Ryan's White' would be a mistake for the study name "Ryan's Daisy".

Dendrobium is an orchid, of course. The synonym of Chrysanthemum is Dendranthema.

Ron, thanks for catching it. I have no idea where I got that from because of I know it's Dendranthema.
I just watched Georgia Gardner with Walter Reeves and he talked about the name change.

I have Ryan's Pink and it is white when the weather is warm and gets pinker when it's cooler. I've been told 'Becky' won't do well here so I haven't tried it, but this one sure does. Also isn't 'Becky' primarily a spring bloomer? My 'Ryan's Pink' doesn't start blooming 'til I think mid-summer, but has by far the longest blooming season of any dendranthemum I've tried here.