Invasive Species are a major problem across the Belfast hills, and in the Colin Glen area. Our park has 3 major invasive species - Himalayan Balsam, Japanese Knotweed and Laurel. These species are not native to the forest, can outcompete our native plants and can also lead to problems like erosion.
From January 2009 the Colin Glen Trust introducted a project to wipe out the invasive species in the park. The Trust took on a placement student, Aline, who took on this project to help eradicate the the different species we have in the park.
Aline first tackled one of the main invasive plant species - Himalayan Balsam - which she found significant amounts of throughout the park. Once she mapped out all these areas it was up to volunteers to come in and help with the eradication of this plant. The best time for us to go and pull these plants was from late May right through to June when they were big enough to identify but not yet in flower. The plan was to have as many volunteers go up the forest and pick as much balsam in one area as we could. Working off of Aline's map, we went from onearea of balsam to the next throughout June...and July...and August! We also discovered a few new areas of balsam along the way that had not been mapped. It became a much bigger project than we ever expected. Even after we had worked through all the mapped areas, we went back over them to get any balsam that was missed - if left to set seed, every pod can produce up to 2500 seeds! Himalayan Balsam needs to be eradicated because it grows fast and can take over large areas of the forest. It also blocks out light to the forest floor, making it harder for our native plants to cope. Many of the patches of balsam were along the river, where the shallow roots of the plant offer no protection to the banks and can lead to erosion.
Another invasive species is Japanese knotweed which was introduced to the UK as an ornamental plant. It is extremely difficult to take out of the forest due to its strong root system. Digging up this plant is difficult, so the only successful option seems to be to treat the plant with herbicide in summer and autumn months. However, we don't like to spray here unless absolutely necessary, so we're hoping to find another way to get rid of the knotweed.
The cherry laurel is an evergreen species which is also an invasive plant to the forest. It was introduced for cover for game birds when the glen was owned by a man named John McCance in the 1700's -1800's. Because of its thick, evergreen leaves, the plant allows little to no light to reach the forest floor. Plus, the roots actually release a cyanide-like substance into the soil, making it harder for other plants to grow around it. Laurel has been here in the forest for so long that it has spread over the years. In the past, the top growth has been cut down. However, the roots were not treated with herbicide, meaning that young shoots could still sprout from the stumps and roots. What we have in the park now are lots of smaller, spindly laurel plants. We're planning to dig a lot out this winter.
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