Does Preen kill everything or can I use it near my flowers?

Not sure about flowers, but website said the following: "Do not use on St. Augustine, dichondra, carpetgrass, or bentgrass. Do not apply near waterways."

I personally would not have this product near my flowers.

It is not a weed killer it is a preventative so yes you can.

I have used it--it prevents germination of seeds, so you can use it when you plant annuals, perennials, etc. I use it in the areas where weeds are really uncontrollable. Check the website if you have questions.

Yes you can use preen around your flowers I have done it for years

I Use Preen in all my beds in the spring and have never had a problem with flowers.