Narrow branch angles can cause structural problems as the tree grows. Close observation of the tree's trunk can reveal problem areas that are easily recognizable, even to the greenest of gardeners. Check for signs of cuts, scrapes or recent pruning. A wound that is more than a quarter of the trunk's circumference is too large and can affect future health. Look for areas that are discolored, sunken or swollen, all of which indicate problems beneath the bark.
Frost damage can cause shallow cracks in the bark.
Nuss adds that the general size of the tree can be an accurate indication of quality. By measuring the trunk diameter at six inches above ground level and the size of the root ball, shoppers can estimate how tall the tree should be. The root ball should be at least 20 inches in diameter. A trunk diameter of 2 inches translates to a tree between 13 and 15 feet tall. The root ball should be at least 24 inches in diameter.