As noted above these plants can get to about 3 feet tall. Hard to tell how a black-eyed Susan will do in Alaska, especially as it becomes acclimated (meaning to the location, light, etc.). Give it a couple/few years to get established (remember the perennial adage: first they sleep, then they creep, then leap). There are many circumstances that might affect its growth and remember that the one you bought may have been forced to bloom and stand as tall as it is. That may/may not happen exactly the same way again. Enjoy it!
As noted above these plants can get to about 3 feet tall. Hard to tell how a black-eyed Susan will do in Alaska, especially as it becomes acclimated (meaning to the location, light, etc.). Give it a couple/few years to get established (remember the perennial adage: first they sleep, then they creep, then leap). There are many circumstances that might affect its growth and remember that the one you bought may have been forced to bloom and stand as tall as it is. That may/may not happen exactly the same way again. Enjoy it!