I've had these two red cestrums in the planters for almost a year now. The one on the right, in front of the white fence was transplanted from a bed along the northern wall as it was not happy there. I thought it would do better in a shadier position, and it has...however, now that I have a sister plant to compare it to, it once again looks rather sad.
The plant on the left, the same type, was bought last year in a 1 gal. pot. It has been thriving since being planted, despite the frequent beatings it has suffered from the mirror behind it blowing down on top of it, thus the 'snail sculpture' in front propping it up after being flattened twice. After pruning the right one down to nothing last year I got some beautiful, lush full growth in spring and thought that this is what these plants needed to stay healthy and bushy, but perhaps it's just a weaker plant, now that the one on the left is going gangbusteres with very few dropped leaves. I pull handfulls of yellow leaves off the right plant every time I go into the garden, and am now constantly nipping in back hoping it will bush out like its sister, but so far with not luck. Their sun posistions are so similar that I can't blame it on light, and the only other difference could be neighboring plants....another one for the mystery file, and perhaps the pull and replant file come spring.