There is some information at the link below. If you would do a Goggle search, you would find more, I believe.
I had Alliums in Ketchikan Alaska and they bloomed well and multiplied quite slowly. What I am trying to convey is that how well they will do depends largely on your location and your soil conditions. I wish you great success.

Here is a link that might be useful: Gladiator Alliums

I have several species of ornamental alliums.
Globemasters, Gladiators and Rosenbachianum have all multiplied.
White Giants, Chrisophii, Schubertii and Mount Everests have not.
jb