The last few days I’ve been removing Himalayan Blackberry from a patch of Salmonberry shrubs. The poor Salmonberry is taking a real beating. Why? I think I can explain it in two words. But first, if you are new to Himalayan Blackberry, let me explain its life cycle, and how it knocks down the Salmonberry.
Life Cycle of the Himalayan Blackberry
Each Himalayan Blackberry plant generates one new vine stem each growing season that lives for two years and then dies. In its first growing season, a vine stem is basically an above-ground runner. It grows as high and far as it can and climbs over anything in its path. Later in the growing season, the tip of the vine grows down towards the ground. If it finds soil, roots start growing out of the tip, and a new plant is established.* In year two, the above-ground runner produces blossoms, fruits, and then dies. At the same time, a new first-year runner starts growing out of the base of the plant and the cycle continues.
Because of its life cycle, the base of a Himalayan Blackberry plant will typically have at least three stems emerging from the ground, two green and one or more brown. The runner and the fruiting stem will be green. One or more dead brown stems will remain until they break off. On older Himalayan Blackberry plants, the stems can be almost an inch thick at the base, the overhead runners can travel 40’, and the dead stems can persist for years.
Why Does the Himalayan Blackberry Flatten the Salmonberry?
Overhead runners. The Blackberry runners literally flatten the Salmonberry shrubs, bending them over, pinning them to the ground, and holding them fast with the dead stems of prior years. Salmonberry thickets spread from underground runners, and new stems can’t bend to the ground to sprout roots and generate new plants. Without human intervention, I’m afraid the native Salmonberry doesn’t stand a chance once it is invaded by Himalayan Blackberry.
*I think this is the main way in which Himalayan Blackberry thickets both expand and become denser over time.