Answer: Based on your description, I am unable to diagnose the problem exactly. However, when a large portion of a plant dies back, it is sometimes due to mechanical injury; this can be fairly obvious such as a broken stem, or a little bit harder to detect such as a dog repeatedly lifting its leg on it. Another possibility is that the roots on that side of the plant are having a hard time becoming established, perhaps due to an underground obstruction or damage from a rodent chewing on them or excess salt from a sidewalk ice melter. Finally, this plant is quite often attacked by scale insects and this can cause substantial dieback. The insects may look like small oyster shells stuck on the stem or you may find small dark waxy disks on the leaves and stems. You might want to consult with your county extension or knowledgeable nursery personnel to see if this might be the problem.
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