Many large lower branches and limbs were removed to raise the canopy of these oak trees 14 feet, leaving tall bare trunks with a small amount of live green leafy canopy at the top. It looks like a lion’s tail, or stalk of broccoli.   

Two years later the tree on the right shows rapid growth on the lower trunk after a year. Ironically, broccoli topping has the opposite effect — it causes rapid and unruly regrowth which is not only ugly, but significantly weaker than the original limbs. The tree on the left has lost vigor and is showing signs of decline

Every cut is a wound. When trees are wounded, they don't "heal" in the same way that we do. Instead, they compartmentalize the damage by forming a callus, a protective barrier of new wood that grows around the wound to prevent further decay and infection, which is ugly.