Himalayan Blackberry, English Ivy, & Scotch Broom
Western Washington's most abundant invasive plants.
Macro-Invasive Plants
Himalayan blackberry, English Ivy, and Scotch Broom are serious threats to native ecosystems and urban habitats in nearly every County in Washington as well as in Oregon and California. While these invasive plants have mostly been removed from Eastern Washington, residents of Western Washington have seen these plants in some form or another growing on the side of highways, in wetlands and rivers, on steep slopes, or even in their backyards.
Simply removing the invasive plant doesn’t mean native plants will regrow into that space. Invasive plants grow faster and out-compete native flora easily. We treat the infested area then install native flora to help give native plants a much higher chance of survival and increase overall restoration success.
We take pride in our ecological soundness. We always use the least toxic and least impactful approach to invasive plant treatments. We are licensed to treat in aquatic areas, and we use special chemical formulations that are non-toxic to salmon, amphibians and other wildlife in their applied concentrations.
A single treatment of herbicide is rarely enough to treat these aggressive, exotic plants. Normal invasive plant control requires multiple treatments over 3+ years. Control techniques could change throughout the year, from manual removal, to broadcast herbicide, to spot applications.
Invasive plants don’t often affect landscapes on the short-term. Thinking long-term: neglected landscapes can become inundated with unmanaged weeds resulting in serious consequences. Long-term preservation and control starts now.
English Ivy: The density and abundance of English Ivy on the ground prevents other plants and trees from growing up and out of the ivy.
Our team has identified English Ivy as a primary cause for forest decline and reduced forest regeneration in Port Angeles, Port Townsend, Olympia and Poulsbo. English Ivy poses long-term threats to steep slope stability, soil loss, erosion, and forest regeneration. We treat English Ivy in the winter when nearby plants are dormant in order to reduce herbicide damage. We use a combination of both mechanical removal, either by hand or by machine, and a special chemical herbicide formula which can break through vines and thick waxy leaves.
English Ivy is most detrimental on shorelines, steep slopes, riparian slopes, and hillsides.
Himalayan Blackberry: Himalayan blackberry produces juicy, plump fruit. When managed and controlled in a small backyard garden, or in a park, the plant is a great food source for humans and birds alike.
However, this plant has a fruiting timeline limited to only a few months out of the year. Birds and other local wildlife populations need a diverse and reliable palette of plants to choose from as a source of food throughout the whole year. But Himalayan blackberry’s aggressive growth pattern can overtake a native forest or riparian understory in a matter of years, resulting in the disruption and reduction of other important food sources.
Blackberry also rapidly grows along trees near streams and rivers, causing those trees to eventually die from lack of water, nutrients, and sunlight. This invasion results in streams and rivers lacking sufficient natural tree cover to shade from direct sunlight, which then increases water temperatures. With increased water temperatures, juvenile salmon and other local fish species are less able to survive. Uncontrolled growth of Himalayan blackberry ultimately contributes to the problem of decreasing salmon populations in Washington State.
Scotch Broom: Scotch broom, a woody-yellow ornamental flowering plant, displaces native vegetation, reduces wildlife food and habitat, and interferes with reforestation by outcompeting tree seedlings for nutrients.
This plant is mildly toxic to pets and livestock, its fragrance can trigger allergic reactions in some people, and it is a highly flammable fire hazard. Seeds in scotch broom can survive for nearly 80 years and persist through both fire and flooding.
Our team controls scotch broom using multiple methods: we cut and extract, topically treat foliage with herbicide, and use tractor tillers.
Case study – City of Olympia
In 2012, principal John Bornsworth, performed a series of forest landscape surveys in Priest Point Park in Olympia. These surveys represented all 300 acres of the park and their forest maturation, forest species present and native regrowth. After analysis of the data returned, it was apparent the areas of the Park infested with a thick ground cover of English Ivy were experiencing no coniferous or deciduous tree regrowth. The invasive Ivy practically arrested natural forest succession. In 20-50 years if left unmanaged, the current trees would begin dying and there would be no younger trees taking their place. In 100 years the 300 acre forest could have had very few naturally grown trees. Using this data, the Park launched a program to drastically reduce the presence of English Ivy.
