Light penetration and happy endings. No, this is not the latest trend with casual relationships on Showtime or HBO. This is about seeing through your trees. No, that's not about a peeping Tom or Big Brother or for Trump keeping tabs on immigrants.
So you want light penetration with most trees for a few reasons:
1. Light that filters through a tree, along with increased oxygen flow, helps keep lower/inner foliage growing so that all the living mass is not only at the top or the outside (liontailing). This is important for balance, strength, taper, and rejuvenation abilities.
2. If light filters through, it means air does too. This decreases wind resistance, so parts of the tree are less likely to break in high winds. Just about any time a tree comes down or loses a member in a high winds or stiff breeze, it could have been easily avoided. More on this in another post.
3. Fewer crossing branches exist if the interior of the tree isn't chock full of dense branches. This is a good thing.
4. You can see the interesting silhouette of the tree if there's light coming though it, especially during sunset or sunrise, and during dormant periods it will look a lot better and cleaner.
5. Trees just look better. I know, some people want lollipops and mushroom trees, but the best trees by most standards have distinguishable branch patterns. This seems to be most evident with upright Japanese Maples, Monterey cypresses, spruces, cedars, Auracarias, and some others that don't come to mind at the moment. This is something that can apply to most other trees with proper maintenance, and all will be well. If you just like the look of a jumbled mess, then I suppose my guidance is just as unlikely to get through to you as the sunshine through your trees.
Trees can live a longer life and everyone can have a happy ending when light penetration is an ultimate goal.