| The height on labels is customarily the height at 10 years of age. Very few happy plants stop growing when they are 10 years old. If you go to Scotland where many plants are 100 years old, you find many rhododendrons that are more than 20 foot tall. The saving grace is that they grow slowly and are easy to prune to keep near the "10 year old" height. |
Here is a link that might be useful: How to care for rhododendrons and azaleas.
