It will take quite a few years for it to max out even under ideal conditions. For example, I planted my 5-gallon Bory over 3 years ago when it was about 5' tall. The new shoots this year got up to 7'-8'. How big a plant are you starting with, and what's your goal? The first several years in the ground you will probably get relatively little growth and culms that may not even be as big as those of the division you're planting.

I found this plant to be *extremely* fast growing. Evidently the Pacific Northwest is well suited to P. Nigra cultivars. I put in a 5-gallon, 5-foot high specimen. Each of the two successive years it doubled in height to 20 feet high. Sadly, I ended up removing it because I was not willing to keep up with its rambunctious nature. Its rhizomes went everywhere, and fast! I replaced it with a Fargesia Robusta. Much more suitable for the location.