To the untrained eye, lemon trees and lime trees look nearly identical, unless they have ripe fruit on them. They both grow in the same regions and have the same general shape, bark texture and color. However, there are some telltale signs that differentiate lime trees from lemon trees. No matter what part of the growth cycle the tree is in, you can tell whether it is lime or lemon in as little as a minute.
Look at the size of the tree. A fully grown lemon tree can grow up to 20 feet tall with widespread branches. Lime trees are generally more narrow and shorter, usually no taller than 13 feet at full height.
Examine the leaves. Lemon leaves are long and narrow, usually around 5 inches long. Lime leaves are more rounded and shorter, usually between 3 and 4 inches long.
Tear a leaf open and smell it. Lemon leaves have a very mild citrus aroma while lime leaves have a bold lime smell.
Examine the flowers if they are present. Lemon flowers grow in pairs or singles and are tinted purple. Lime leaves grow in small clusters and are completely white.
Examine the fruit if it is present. Lemons are pointed on both ends, much like a football, and have thick skin. Limes are more rounded, like a basketball, and have thin skin.