I usually left them up a little bit because they are usually interesting after they are done blooming. But once it looks ugly cut it down. Generally the leaves on Alliums aren't that bad and soon go brown and can be disposed of. Did you have any unusually hot days? That will shorten the bloom time.

Thank you for replying. We had a relative cool spring this year. It's been great. I have been able to get so much more done outside. I've planted some coneflowers amongst the alliums.

When can I transplant Globemaster, Ambassador, and White Giants? Do I dig up and store till fall after the leaves are yellow? I really want to keep them all and need to thin out the bed they are in. I just want to move them somewhere else.

Thanks
kentstar

http://andyswebtools.com/uploads/1202/Alliums_News_Letter.pdf
I did a little searching and found this site. I am not sure you can get this site from here as I am pretty amateur when it comes to the computer.
If you can't, this is what I discovered:
Dig up in the fall after foliage has died off. Also, bulbs should be the size of the 'giant pencils'.
Hope this helps.
I did a google search putting in transplanting globemaster allium

Here is a link that might be useful: andys web tools

Whoops. I have the website wrong. It was Gardening Geek Alliums