Coreopsis grown as a perennial should be cut back after the summer growing season. Cut back one-third to one-half of the plant's height. Pruning should not extend into the older brown woody growth, as this may kill the plant, according to the University of California Cooperative Extension.

Will coreopsis rebloom if cut back?

During Blooming Season

You may value coreopsis plants for their blooms, which often last through the end of summer. But you won't get maximum blooming unless you deadhead, or cut off finished flowers, regularly. Using pruners, cut off spent blooms at least once a week before they go to seed.

How do you prune coreopsis for winter?

All you have to do once the earth thaws and all danger of frost has passed is cut the dead stems down to just two to three inches above the ground, and new flowers will grow. If you must have a neat, clean look in your garden throughout the winter, you can cut your coreopsis down to four to six inches above the ground.