It does help to deadhead a lot of the perennials. It will help them to bloom a little longer. The Stella's are helped a lot by deadheading as they can put that energy toward new blooms. My Stells'a do not bloom much during the really hot part of summer but will again after the weather cools some in early fall. I don't get all my deadheading done, especially on my gaillardia, which reblooms even when I don't keep up with them, but look much better if I keep them groomed. The heat and me don't get along real good and we have so much food crops that have to be picked now and when we get done with them, I'm finished for the day, no deadheading.

Wish I could tell you on the coneflowers---I let mine seed-harvest the seed heads and take them up to a school near here that has left the banks arround the playground native. Hope to have some going strong there before too long.

Plants have one biological function - reproduce. Since flowers produce seeds for the propagation of the next generation, if you deadhead the first flowers the plant will produce more. Flowers produced in July/August (for zones 7 and above, later in below 7) should be allowed to go to seed. This tells the plant it is time to shout down.

I dead head my daisies until about the end of July. I get sporadic reblooms by dead heading. Never the glory of the whole bed in bloom like the first flush of flowers, but still enough to cut and bring in.

Glenda