Blackberries are a popular fruit, but their thorny canes are a common feature for anyone who has picked them. These sharp outgrowths play a significant role in the plant’s survival and propagation, sparking curiosity about their purpose.
The Evolutionary Purpose of Blackberries’ Thorns
Blackberry thorns are a primary defense mechanism, developed through natural selection over vast periods. These sharp structures deter herbivores from consuming the plant’s leaves, stems, and developing fruit. By making the plant less appealing, thorns enhance the blackberry’s chances of survival and successful reproduction, especially for young, vulnerable tissues.
The presence of thorns allows the blackberry plant to invest energy into growth and fruit production rather than constantly repairing damage from browsing animals. This evolutionary advantage meant plants with more effective thorns were more likely to survive and reproduce. This process led to the widespread prevalence of thorny blackberry varieties.
While birds can access ripe berries for seed dispersal, thorns discourage larger mammals that might consume the entire plant. Thorns also help the plant physically establish itself, with some species using them to cling to surrounding vegetation for support. This dual function of defense and physical support is important for the plant’s ecological strategy.
Anatomy of Blackberries’ Thorns
Botanically, the sharp structures on blackberry plants are “prickles,” not true thorns. True thorns are modified branches with vascular tissue, originating deeper within the woody stem and difficult to detach. Blackberry prickles are outgrowths of the plant’s outer epidermal layer and can be removed more easily, similar to how a fingernail can be removed.
Prickles lack internal vascular bundles, distinguishing them from true thorns or spines. They are sharp, pointed, and often curved, with their orientation along the stem contributing to defensive effectiveness. This physical form makes it challenging for animals to grasp or consume the canes without discomfort, serving as an immediate deterrent.
Thornless Blackberries: A Human Innovation
For centuries, the sharp prickles of wild blackberries presented a challenge for cultivators and harvesters. To address this, humans developed thornless blackberry varieties through selective breeding. This innovation has made harvesting significantly easier, reduced injuries to growers, and increased the fruit’s appeal for home gardeners.
Thornless varieties often originated from natural genetic mutations, which breeders exploited through cross-breeding. Some thornless traits are linked to recessive genes, while others are dominant, influencing how they are passed down. Popular thornless cultivars include ‘Navaho’, ‘Arapaho’, ‘Ouachita’, and ‘Chester’, offering good yields and flavor.
While thornless varieties provide practical benefits, some traditional thorny types are often more vigorous or hardy in certain environments. Early thornless varieties sometimes had trade-offs, such as reduced hardiness or less robust growth.
Modern breeding efforts continue to improve these characteristics. Today, many thornless cultivars are comparable in fruit quality and yield to their thorny counterparts, providing a convenient option for growers.