I like to ground the trees with bushes at it's base and dark shadows there. That method seems to work well.
Making that trail meander into the painting was fun...gives the painting some added depth too. The grasses you see here are just vertical strokes with a knife. The base for the grasses are just vertical scumbling with the knife done prior to any grass blade highlights. The dirt areas are also scumbled in with a knife...to finish that off I flick tiny grasses up into the dirt from below. A fun painting to do.