Plum trees bear a delicious, round, purple fruit. When you're looking at a plum tree that has ripe plums, there is no question of the tree's type. If the tree is blooming, you can tell it apart from other trees because of its small, white flowers. However, even when the tree isn't bearing fruit, or blooming, you can still identify the plum tree by identifying the plum tree leaves.
Look at the shape of the leaf. Plum tree leaves can be ovate (egg shaped), oblong (almost cylindrical), obovate (almost fan-like) or elliptical.
Look at the edges of the leaf. Plum tree leaves are serrated around the edges. The serrated blades are usually thin and not very sharp.
Feel the leaf and look at its texture. Plum tree leaves are "pubescent," which means that they look and feel smooth but hairy -- a little like bumfluff.
Observe the size of the leaf. Plum tree leaves are generally between 5 and 10 cm (2 and 4 inches) long.
Look at the colour of the leaf. Plum tree leaves come in various colours, but the colours are usually green, chartreuse (yellow-green) or purple during the spring and summer, and yellow, orange, red or purple during autumn.