Blackberry bushes (Rubus genus) are a source of both prized fruit and significant landscape frustration. While the answer to whether they are invasive is complex, non-native varieties are profoundly problematic for many landowners. These plants, with their aggressive growth and thorns, rapidly colonize disturbed areas and overwhelm other vegetation, making established thickets extremely difficult to remove.
Defining Aggressive Growth Habits
The aggressive behavior of certain Rubus species is defined by their ability to rapidly dominate an area and form dense, impenetrable thickets. This habit creates a monoculture, where a single plant species monopolizes resources and severely limits biodiversity. Aggressive blackberries outcompete native plants for sunlight, water, and soil nutrients, fundamentally altering the local ecosystem.
A single non-native plant, such as the Himalayan blackberry (Rubus armeniacus), can spread into a six-square-yard thicket in less than two years. This rapid expansion results from perennial root systems supporting biennial canes that grow vigorously. Their dense, thorny structure hinders access for both humans and wildlife, reducing the land’s ecological value.
Identifying Invasive Versus Native Species
Accurately identifying the type of blackberry is the crucial first step, as native species are less problematic than non-native invaders. The most commonly recognized invasive species are the Himalayan blackberry (Rubus armeniacus) and the Evergreen or Cutleaf blackberry (Rubus laciniatus), both introduced from Eurasia. Himalayan canes are robust and angular, often having five sides, and are armed with large, hooked thorns.
In contrast, native North American blackberries, such as trailing or high-bush varieties, have less vigorous growth and are less densely armed. Native species typically lack the white-felted underside of the invasive Himalayan type, having leaves the same color on both surfaces. The Evergreen blackberry is identified by its deeply dissected, almost fern-like leaves. Native species do not form the massive, landscape-altering thickets that the non-native varieties do.
Biological Mechanisms of Spread
The formidable nature of blackberry bushes stems from their use of multiple, effective biological propagation strategies. One significant method is tip rooting, or tip layering, where arching canes bend until the tip touches the soil. Once contact is made, the tip spontaneously forms roots, establishing a new, independent plantlet that extends the thicket’s reach.
A second method involves root suckering and the use of rhizomes, which are underground stems that spread laterally from the main root crown. These rhizomes sprout new shoots, creating a dense cluster of genetically identical plants around the parent. The extensive, deep root systems allow invasive species to survive drought and store energy, making them incredibly difficult to remove entirely.
Finally, blackberries reproduce through seed dispersal, allowing the plant to colonize distant areas. The berries are consumed by various animals, including birds and mammals. As the seeds pass through the digestive tract, the hard seed coat is scarified, which improves germination once deposited in new locations. These seeds can remain dormant in the soil for years, creating a persistent seed bank that fuels future infestations.
Effective Strategies for Removal and Control
Managing aggressive blackberry bushes requires a persistent, multi-year approach that targets all three mechanisms of spread. For small patches, physical removal is the most effective long-term strategy, involving digging out the entire root crown and all lateral roots. It is crucial to remove as much of the root system as possible, as small root fragments can resprout into new canes.
For larger infestations, repeated mechanical control is necessary to starve the extensive root system. This involves cutting, mowing, or flailing the canes back to the ground multiple times throughout the growing season, typically at least four times per year. This repeated defoliation depletes the plant’s stored energy reserves, eventually weakening and killing the roots.
When mechanical removal is impractical or insufficient, chemical control using targeted herbicides like triclopyr or glyphosate can be applied. The most effective timing is often in the late summer or fall when the plant is actively transporting sugars to the roots for winter storage. Herbicide can be applied as a foliar spray or as a cut-stump treatment to freshly severed canes, ensuring the chemical travels directly into the root system. After successful removal, the area should be replanted with vigorous native species to crowd out emerging blackberry seedlings and prevent re-establishment.