I've done it both ways on an all B&W handdrawn map:

I've done "individual" trees (basically triangles and circles with lines out their bottoms) and I've done the large scalloped squiggly line (shadded in with more squiggelies) and lines coming out the bottom of it, too. I started using the second when I wanted a half-decent map, but didn't want to take the time to draw hundreds of circles and triangles on sticks. But, truth-be-told, I always preferred the circles and triangles on sticks.