So my mother gave me this Bonsai Ponytail last year for Valentine's from Costco (it came in the mail....) Within a few weeks all the foliage at the top fell out. I eventually stabilized it and as you can see have some sprouts coming out the side. I thought the top foliage would eventually regrow, but sadly it hasn't. Is there anything I can do to stimulate it?

Also I live in cold Wisconsin in an apartment and it has a sun lamp that it shares with some other plants. I have given it Osmicote and Miracle Gro every few months. Other than that it gets water when it needs it, a bit every few days. This is my first Bonsai and I'm proud it is still alive, particularly after how it reacted the first few days.