
Gave it a little more form with the bright colored leaves, blended the trunk into the leaf contrast better to make it uniform, shaped some leaves to give the tree a bit more sense of clear form while maintaining the 'impressionist' sense you were going for.
The grass is still a bit too bright imo, but it works to balance the image contrast as long as there isn't too much of it.
Also, I personally would advise against adding more colors and going with the ones you have here. They are chosen fairly well and work together nicely.
A few suggestions:
1) Unless you're going for a /really/ abstract or digital look, I'd advise against going for really squared-looking leaves -- impressionists did use blending to smooth their forms in some places.
2) Your line-work is really nice, but I suggest either going for a fully drawn look or a fully silhouetted look -- the latter is more useful for painterly-looking styles like this one (and by 'silhouetted', I mean start with a flat-color-filled silhouette and work in your shadows and highlights from there for form instead of drawing nice lines as you might for larger, but more "specifically-detailed", structures or characters, since removing those lines on such randomized details is a lot more work and tedium in the longrun than simply not having them there at all to start with).
3) The variation in outline color periodically across the image's edge really makes the form look too chaotically 'outlined' and lends nothing to the 3d form of the image, so I suggest only using the shadow color around the edges to hint at more leaves along the edges, on different 'layers', instead of using the darkest colors just for the sake of separating the subject from the canvas color. I didn't fix this issue much in my edit except for the bottom portion on the shaded side of the tree leaves and some along the left and right sides of the leaves, but I did that to give you a clearer idea as to what I'm talking about so you can get a sense of how to apply it to the more lit portion of the tree.
Anyway, that's all I've got for now. Your drawing looks great btw -- I just thought you might be going too much for a 'concept-art' look than you probably really wanted to, so I addressed that in my edit a bit. Hopefully that helps.
