These get a lot bigger than this. Cutting it back is not going to make it healthier. And these respond to hard pruning by throwing out long snaky, seldom branching shoots as they rush to replace the original volume of the top. In other words cutting it back will make it less dense rather than denser.

If you think it has developed some kind of health problem you need to find out what that is and address that directly, instead of whacking the plant back in the hope that will cause it to reinvigorate. And throw off whatever is affecting it.

Thank you for the advice! I took some pruning shears to it while it was in Bloom last summer. I thought that may be the reason why it was rather sparse this year. I’m pretty good about cutting out any suckers that look sad. Any time of year specifically that it likes to be pruned?

Hello tomsthumb, generally this type of shrub should be pruned in late winter and early spring. I think I'm a little late with the answer. Although I would like to know how your plant is currently. Health! :)