It is often shade or overly rich soil that makes perennials flop. Cutting those they have this tendency back by half earlier in the season often really helps.

My soil certainly isn't overly rich, so i expect it is the shade. I find it quite frustrating. These perennials were slow growing in our cool, grey spring and then grew very quickly when the sun came out. Thanks for the response.

Dotty, I think our weather has had something to do with it at least this year. I've got a shasta daisy (Summer Snowball) in full sun over 5 feet tall. I didn't stake it so right now it's laying flat on the ground :(. This shasta has never grown over 3 foot before and never needed staking.

Annette

Hi Annette. The worst ones for me are the Gloriosa Daisies which are 5 feet tall. I was hoping someone would say that they need x fertilizer to strengthen their stalks! I guess there is no quick fix.

No quick fix this year.
Move them to an area where they they get more sun, less water and fert, and they will do just fine. Daisies are tough plants. You've been too nice to them. Give em' some tough love.

Botann, are you sure you don't have a magic fert? Darn. I didn't think I'd ever be accused of being to kind to my plants I love daisies, so I will try to relocate. Problem is, the darned trees keep growing and before you know it, the sunny spot becomes shady. Thanks for responding.