I find the structure of both wanting as both have stems that are a little less than a metre without branching. It looks like a case of strong apical dominance.
I have to keep the dipladema reasonably small because I will have to bring it in each fall (the horticulturalist I spoke to when I bought it told me to bring it in before it gets hit by frost since it is not winter hardy here, just north of Toronto - she didn't say what to do to over-winter it inside or what to expect it to do).
Both are giving a terrific display right now.
Do you have any experience pruning these shrubs? If so, when is the best time of year to prune them? And when you prune, should the focus be on thining the plant, or reducing the height? In both cases, how much should be removed? Can I thicken up the plants by snipping the shoots just below the growing tip of each stem I want to branch? If so, how much should be enough to end apical dominance in these plants and encourage the stems to branch? Am I right in expecting that doing so will improve their displays next year?
Thanks for your time.
R.E. (Ted) Byers, Ph.D., Ed.D. R & D Decision Support Solutions http://www.randddecisionsupportsolutions.com / Healthy Living Through Informed Decision Making