I know this gets asked each season but it is only this year that it really matters to me :).

Last September I removed 4 full grown CAMPFIRE roses (too big and too Japanese Beetleee ;)).

At that same time I replaced the roses them with the perennial rudbeckia LITTLE GOLDSTAR:

Also that Fall I planted a mix of red and white tulips above and below the arc of the LGoldstars

Here they are as of May 27 2019 (you can spot the LGoldstars down the middle):

And as of today I have cut back all the tulip flower stems leaving only the leaves and have planted in between, pink and white geraniums.

Given that the tulips were in full bloom as of May 27, what do you advise as to when I can safely cut back the tulip leaves knowing that the bulbs have taken in enough nutrients giving them the most chance of returning next spring. (I think 6 weeks is the rule of thumb but is that counted from...when the tulips are in full bloom or.....?)

Thanks for your help and experience.