Himalayan Blackberry (Rubus armeniacus)
Himalayan blackberry is an invasive species that has become a significant problem in many regions around the world, including the Pacific Northwest of North America, New Zealand, and parts of Europe. It is a perennial shrub that can grow up to 4 meters in height, and its branches are covered in thorns. The leaves are large, and the flowers are pink or white. The plant produces sweet, edible berries that are popular with humans and wildlife alike.
The Himalayan blackberry is considered invasive because it can out compete native plant species and create dense, impenetrable thickets that reduce biodiversity and wildlife habitat. The plant is particularly well-suited to disturbed habitats, such as roadsides, streambanks, and forest edges, where it can quickly establish and spread.
Control methods for Himalayan blackberry include mechanical removal, chemical treatments, and grazing by livestock. However, these methods can be challenging and expensive, and often require ongoing management to prevent regrowth.
Reproduces by seed and vegetatively by rooting at stem tips to form daughter plants, and sprouts from root buds. Plants begin flowering in spring with fruit ripening in midsummer to late August. Thickets can produce 7,000-13,000 seeds per square meter, and seeds can remain viable in the soil for several years. Fruiting stems generally die back at the end of the season, but non-fruiting stems may persist for several years before producing fruit. Dispersal: Primarily dispersed by root and stem fragments. Birds and omnivorous mammals, such as foxes, bears, and coyotes can consume berries and disperse seeds. Humans also contribute to blackberry spread by purposefully planting canes.
The first step in controlling invasive blackberries is to cut down the canes to a point just above the ground. Next, you can either dig up and dispose of the rhizomes (root crown) or spot treat the tips of the canes with herbicide. Most of us would like to take the organic approach, but digging up a large thicket can be overwhelming. After digging out what you can, rototill the area several times during the season to make you have destroyed any bits of rhizome and crown left in the ground.
Mowing, including the use of riding mowers and tractor-mounted mowers, can be very effective, but can also harm desirable species. If roots are not manually removed, mowing several times per year over several years is necessary to exhaust root reserves. If mowing or cutting is only done once per year, it should be done when the plants begin to flower. Do not mow where soil is highly susceptible to compaction or erosion, or where soil is very wet.