The Himalayan Balsam Eradication Project at Pigeon Lake, Alberta
A noxious weed removal success story
About ten years ago, a new plant appeared on the shoreline of Pigeon Lake. Each year it was continuing to advance along the shoreline and was becoming the predominant plant species. People loved its beautiful pink flowers and thought it was a welcome addition to the lake. But then it was found to be a noxious weed: the Himalayan Balsam. In 2009, an action plan for this plant was devised.
The plant is introduced to gardens through seed purchases and plant sharing. If left uncontrolled, the seeds can shoot out as far as ten feet when the seed pods explode. After seeds reached the lake, the Himalayan Balsam quickly spread along the shoreline through wave action and currents. By the time the eradication program started, the plant had spread roughly halfway around the lake over a distance of about 25 km. The plant also was found in some forested areas of the watershed as a direct result of the dumping of garden and beach rakings into the bush. This plant is classified as a prohibited noxious weed by the Alberta government, which means the plant must be removed.
The initial eradication plan encouraged the lakeshore residents to pull and bag the plant as is the recommended practice for noxious weeds. But it soon became apparent that this strategy was not working. There were just far too many plants. Bagging of the plant was found to be slow and cumbersome. With thousands of plants going to seed, it was clear that a different method was required.
It was found that if the plant was pulled out by the roots, a very easy job because of the shallow root system, and the stem was broken, also an easy task as it snaps like a piece of crisp celery, the plant quickly died. This prevents advancement from the flower to seed stage and stops any re-rooting of the plant. If the plants are piled together, the bottom plants can maintain sufficient moisture to continue growing, but if dropped separately, they will die. So a new protocol was developed: Pick, Break and Drop. If done before the seed pods fully develop, this protocol has been found to be 100% successful in killing the plants.
For the first three years of the program, the goal was simply to destroy as many plants as possible. From the first of July, the shoreline on the lake was patrolled biweekly to remove the plants. It was found that these patrols were required until the end of September as new plants continue to germinate until the first frost of the season.
For plants with fully formed pods, the technique was adjusted slightly to collect any mature seeds and prevent them from forming new plants the following year. The top part of the plant, that part where the mature seed pods will have formed, is bent over and carefully placed inside a plastic bag. At this stage, any contact with the seed pod will cause it to explode and the seeds will “shoot.” Once inside the bag, the stem can easily be broken. This process is then repeated for any other seed clusters on the plant. After all the seed/flower clusters have been removed, the remaining plant can be picked, broken and dropped.
After six years, the shoreline is now free of this plant. The “Pick, Break and Drop” protocol proved to be entirely successful. Once the plant is removed from the ground, it quickly dies, as long as it is not dropped in wet soil or piled with other plants.