Hey Anita--

In my experience, yes a tuber does reach its mature height in year one----but it/they are slower to get there. Of course, I've not taken a tape measure to my plants and there may be variations of a few inches or so but nothing noticible to the eye.

In my opinion, clumps are simply unpredictable. Some of mine are shorter than the others of the same name---have more sprouts climbing on the ground before I notice and can stake them, and simply have less flowers.

Good luck,

Patricia