You shouldn't save a pixel work as jpg, but as either gif or png.
Have you plotted out in your mind what actually happens to the trunk once it disappears inside the leaves? Also, there are like 40 leaves on that tree. An oak tree can have up to 200.000 leaves on it, so when drawing a tree, it's usually better to try to depict what a mass of leaves looks like in general rather than draw out every single tree. A bit like when drawing a beach, you don't draw it by drawing each sand grain separately. However, if you want a more cartoony style then it's ok to draw separate leaves as well, but even then they are particles that together create separate masses of leaves.
Anyway, welcome.
Drawing trees is one subject I'm very passionate about, so you'll see me nagging about it a lot.
