Is it possible to divide Coreopsis and if so, when should this be done?
The coreopsis plant is the 'Sunshine' variety.
Certified GKH Gardening Expert
This is best done in early spring. They usually reseed each year, so there will be plenty to choose from. If you would like to take a tip cutting, take the tip of the plant before it flowers, and root it in rooting hormone and perlite, or other rooting media.
This article will help you to grow these plants: https://www.gardeningknowhow.com/ornamental/flowers/coreopsis/growing-coreopsis-flowers.htm