Blackberries belong to the large and diverse Rubus genus within the rose family, Rosaceae, which also includes raspberries and dewberries. These plants are generally found growing in thickets along disturbed areas, forest edges, and fields across many regions globally. Accurate identification is important for anyone interested in foraging or cultivating these popular fruits. Identifying a blackberry plant relies on observing its permanent physical structures, such as its stems and leaves, and confirming these observations with its seasonal reproductive features.
Identifying Canes, Thorns, and Leaves
Blackberry plants have semi-woody, biennial stems called canes. First-year canes, or primocanes, emerge from the root system, focusing on vegetative growth and reaching heights of two to six feet. These primocanes are often stout, light green to purplish-red, and frequently display an angular, furrowed, or ridged structure, which helps distinguish them.
Second-year canes, or floricanes, are the stems that survived the winter and produce flowers and fruit before dying back. Most blackberry varieties have sharp prickles or thorns covering these canes. These prickles are typically stout, straight to slightly curved, and have a broad base where they attach.
Blackberry leaves are compound, composed of multiple leaflets. Primocanes often have palmately compound leaves with five leaflets, while floricanes may display leaves with only three. The leaflet edges are sharply serrated. Leaflets are medium green on the upper surface, often with indented veins, and noticeably paler on the underside.
Seasonal Confirmation by Flowers and Fruit
In late spring, floricanes produce showy flowers, confirming the plant’s identity. Blackberry flowers are typically white or sometimes pale pink, consisting of five distinct petals. These petals surround a central cluster of many stamens and pistils. The blooming period usually lasts around three weeks before the flowers transition into fruit development.
Blackberry fruit is an aggregate fruit, composed of numerous small, fleshy sections called drupelets. Each drupelet contains a single seed. The fruit color progresses from green to reddish before ripening to a deep, glossy purple-black.
The most defining characteristic of a ripe blackberry is its structure when picked. Unlike a raspberry, the blackberry fruit detaches while retaining its central core, known as the receptacle. This receptacle is a whitish, spongy center that remains inside the fruit, leaving the base of the picked fruit flat or solid.
Distinguishing Blackberries from Look-Alike Species
Blackberries are frequently confused with other members of the Rubus genus, such as raspberries and dewberries. The simplest distinction is the fruit structure upon harvest: raspberries leave the receptacle on the plant, resulting in a hollow fruit, while blackberries retain the receptacle, resulting in a solid fruit with a whitish center.
Beyond the fruit, raspberries tend to have rounder canes often covered in fine bristles or scattered, hooked thorns, sometimes with a whitish coating. Blackberry canes are more commonly stout, angled, and armed with rigid, broad-based prickles. Black raspberries, which also ripen black, can be identified by their glaucous, or bluish-white, stems and the fruit’s hollow center.
Dewberries are a close relative that produces black fruit similar to blackberries. The primary difference lies in the plant’s growth habit: dewberries are trailing sub-shrubs that grow low along the ground, rarely exceeding two feet in height. Blackberries, in contrast, typically grow as upright or arching, self-supporting canes.
The invasive wineberry (Rubus phoenicolasius) is distinguished by its unique characteristics, even though it is a type of raspberry. The wineberry has distinctive stems and sepals densely covered in reddish, glandular hairs, giving the plant a fuzzy, red appearance. While the fruit is a bright red-orange, the plant is still identified as a raspberry because the fruit leaves the receptacle behind when picked.