If they look awful, you can cut them back, but its usual to wait till the leaves start autumning, and that varies from area to area. Even if you don't cut back, the leaves will yellow and drop off on their own eventually.

I like when they turn yellow, but when they lay down & go mushy, I cut them.

I also wait until they turn yellow and then when they go yucky I remove them then.

Thanks, Folks.