Dallas Park and Recreation is treating water hemlock at White Rock Lake with pesticides.
The licensed applicators began work Wednesday and are finishing today.
Water hemlock can be toxic if consumed or touched; once the plants are treated with chemicals and start to wilt, the toxicity drops, said Brett Johnson, an urban biologist with the park department.
Water hemlock, which grows up to 1 meter in height and prefers wetter areas, has small, white flowers that grow in clusters.
Park staff are also installing a new roof at Big Thicket. Two small tree limbs over the roof will be removed as part of this project, which was scheduled to begin Tuesday and is expected to be completed by the end of the week.