Certified GKH Gardening Expert
Pinching the blooms will help the plant focus more on new root growth when first planted, but with annuals, this may not help too much in the long run. It won't hurt though, so it comes down to a matter preference. Pinching now will result in a bigger set of blooms at the end of the season - but you use the blooms at the beginning. Not pinching will result in a less showy display at the end of the season, but you get flowers faster.