I have a bougainvillea pre bonsai that I got from Wigert's last fall. They had had some hail so it arrived without a lot of leaves and potted in mostly bark. I kept it in the greenhouse which gets pretty cold in winter (down to 40F) and it never really did much except for dropping some of the leaves it had. I figured it was probably semi-dormant and didn't worry about it too much. When the weather warmed up this spring, I kept hoping it would leaf out, but it would just put out a couple leaves and then they would turn yellow and fall off. Finally I thought it might do better repotted into well drained bonsai soil, so I repotted it about 2 months ago. It promptly responded by flowering wonderfully, it was just covered in pink bracts for the last 2 months. But, it still won't grow leaves. It tries to, but as soon as the leaves get full size, they yellow and drop off. I water it almost daily but it is in a very well drained mix so it isn't getting too wet. I don't see any signs of pests. Any idea what is going on?