Crassula Tetragona, losing its needles?

[volvogrrl]

Ive got a lovely crassula tetragona in my possession that I have had for a few years. Over the last year or so, it has shed alot of its 'needles' and so now, it has a tall stalk with needles only at the ends. It looks pretty sad, and I know that they can keep them down the whole stalk; so what has happened? Did it get too much sun? Rootbound? I plan on snipping the long stalks and restarting them, but will the 'trunk' left behind stand any chance at growing the needles back? It has lived outside the entire time I have had it on the central coast of California.

thanks for any help