14 Mar March 2023

Did You Know some Aquatic Plants are Good for Smith Mountain Lake?

In this month’s Lake Matters, SMLA’s Submerged Aquatic Vegetation (SAV) Committee Chair, Joanne Houpt provides timely information about a common water plant, becoming more common here at Smith Mountain Lake (SML).
Water willow (Justicia americana) is an herbaceous, aquatic flowering, native plant to Virginia and SML that grows in the lake to about 3 feet of water depth but also can grow along shorelines. The Department of Wildlife Resources (DWR) has planted some areas of the lake over the years with water willow because it transplants well, provides nursery habitat for juvenile fish and is a food source for herbivorous fish. This plant can grow over 3 feet tall and has narrow 6-inch leaves that are linear or sword-shaped. The small white flowers of this native plant can be seen throughout the summer and the plant spreads under water. Slender rhizomes, or specialized roots, can produce colonies of about 1,000 square feet or more, over time.
Other native wildlife feed on water willow, in addition to fish. Deer and turtles will browse the leaves, and beaver and muskrat will consume the rhizomes. After aquatic plants die off in the fall, the decomposing vegetation provides food (called “detritus”) for many aquatic invertebrates. Submerged portions of all aquatic plants provide habitat for many micro and macro invertebrates. Invertebrates, in turn, are prey for fish and other wildlife species (e.g., amphibians, reptiles, ducks, etc.).

Water willow can be planted in non-riprapped shoreline areas to help reduce erosion from normal wave action. However, in areas of significant wave action the plant does not thrive. Transplanting may easily be accomplished by either planting cuttings or the rhizomes. DWR recommends transplanting in mid to late summer, as mature plants transplant more successfully. They recommend that plantings be protected from hungry fish through use of some type of cage or exclusion device.
A note of caution: water willow does form dense mats, and while it can be cut or grazed, it can be difficult to control and eradicate. It can be controlled through use of herbicide, however use of herbicide to treat aquatic plants is illegal, without proper licensing.
Water willow is becoming more common on the lake. Keep an eye out for those pretty white flowers all summer long. If you decide it might be right for your shoreline, have a plan to control it.