Jay7 I have grasses around the cosmos too...., miscanthus variegatus, deschampsia which has loved the rain by growing very tall and Calamagrostis Karl Foerster. May seem a waste but one group of white cosmos grew to 6 feet and were flowering we'll but were too imposing over the other plants alongside so I dug them up.I now have many plants now coming into flower and I think it's because the weather is warmer now so your cosmos will certainly flower and prob better for being later and putting on so much growth