Riding among trees presents a particular set of entertaining challenges, but there's a good reason to venture beyond groomed resort runs–the snow. In the shady, wind-blocked confines of spruce and fir glades, and among tightly spaced aspens, powder often remains long after a storm.
Aside from the prerequisite protection of goggles and a helmet, tree riding can be made easier by looking ahead and focusing on the open spaces between the trees. Decent board control doesn't hurt either.
Looking ahead, farther down the hill in the direction you're aimed, allows you to process visual information sooner. The earlier you spot an obstacle or terrain feature, the longer you have to react to it. Use driving as an example: Imagine focusing just a few feet past the hood of your car while cruising at freeway speeds. Wouldn't give you much time to react to what you see, would it?
Practice looking ahead by following other snowboarders while riding open runs; focus on their goggle strap or helmet. Becoming aware of looking up will probably be enough to get you to do it–that and the prospect of hitting a tree.
Also like driving a car, it's a natural tendency to veer toward where you are looking. Because our eyes also control direction, focus on the open areas of snow where you'd like to ride, and avoid fixating on a tree (deer in headlights). The white snow should naturally grab your attention.
Tree Picks: The challenge of riding in the trees is that there's no set pattern to them, they're different everywhere you go. In that respect, any resort that has trees (some resorts entirely above timberline don't) is a good place to ride them. A few spots that are actually renowned for great tree riding are:
Steamboat Springs, Colorado: Aspens are their claim to fame.
Stowe, Vermont: Local riders do their own glading by secretly cutting back the trees. Keep your eyes peeled on the way to Smug's.
Heavenly, California: White pines on the upper part of the mountains are naturally spaced out; the Nevada side is especially good.