Identifying a plum tree requires observing a combination of physical characteristics, as focusing on just one feature can lead to confusion with other trees in the Prunus genus, such as cherries or apricots. Plum trees possess several unique traits in their bark, leaves, flowers, and fruit that, when examined together, provide a reliable way to confirm their identity. Careful examination of the tree’s structure and its botanical details will allow for accurate identification even when the tree is not bearing fruit.
Examining the Bark and Tree Shape
Plum trees are typically smaller than many shade trees, often reaching a mature height between 10 and 30 feet, and sometimes they grow more like large shrubs. The overall structure can be somewhat spreading or vase-shaped, though this varies greatly depending on the specific cultivar and whether it has been pruned. Wild or uncultivated varieties may also exhibit spiny twigs, which is a helpful distinguishing feature.
The bark of a young plum tree tends to be smooth and may have a slightly shiny, dark brown appearance. As the tree ages, the bark transforms, becoming scaly, fissured, and developing a grayish-brown hue. A close inspection of the bark often reveals small, horizontal lines called lenticels, which are pores that allow for gas exchange.
Distinctive Features of Plum Leaves
Plum leaves are simple, meaning each leaf is a single unit. They are typically oval or elliptic in shape, often described as teardrop-shaped, with a short, distinct point at the tip. These leaves are arranged alternately along the branch.
A defining characteristic is the serrated margin, meaning the edges of the leaf have fine, sharp teeth. The surface of the leaf is usually smooth on the top side, while the underside may be smooth or sometimes slightly downy, depending on the species. Leaf size generally ranges from about two to four inches in length.
A particularly specific and telling detail is found on the petiole, the small stem that connects the leaf blade to the branch. Near the point where the petiole meets the leaf blade, a plum leaf will often have a pair of small, raised bumps or dots, known as petiole glands. These glands, which can be yellow-green or dark brown, are a classic marker of the Prunus genus and are a key element for precise identification.
Identifying Characteristics of Plum Flowers and Fruit
The appearance of the reproductive structures offers the most definitive confirmation of a plum tree. Plum flowers typically emerge early in the spring, sometimes just before or simultaneously with the new leaves. The blossoms are usually white, though occasionally pink, and possess five distinct petals.
Plum flowers often grow in small groups of one to five together on short stems, called spurs. Each flower contains numerous prominent stamens surrounding a single female pistil.
The fruit of the plum tree is classified botanically as a drupe, a fleshy fruit characterized by a single, hard pit or stone encasing the seed. Plum fruits are generally round to oval in shape and can vary significantly in size, ranging from two to seven centimeters in diameter. Fruit colors are diverse, including hues of red, purple, yellow, green, and blue-black.
A final identifying feature is the distinct suture line, or groove, that runs longitudinally down one side of the fruit. Mature plums are often covered in a natural, dusty-white or pale-blue waxy coating known as “wax bloom,” which gives the fruit a soft appearance and easily rubs off when touched.