The Strategy: This introduced Asian species Hydrilla (Ydrilla verticillata) came to invade our world by the Aquarium Trade Industry. This plant is considered the most problematic aquatic plant in the U.S. It has heavily invaded most of the coastal regions of the U.S. and was recently found in a hot springs area near Bruneau, Idaho by an aquatic weed specialist who was duck hunting at the time (welcome to our world). This plant was probably dumped there by someone who was getting ‘rid’ of the pet fish in their aquarium that they no longer wanted. This plant has 5-8 leaves per whorl, which all of our native aquatic plants are three or less. This plant reproduces by buds near the base of the leaves, tubers attached to the roots, and above and below ground stems. The greatest way this plant spreads is by fragmentation. The leaves have a very distinct characteristic in that the underside of the mid-vein has a saw-toothed (rough) ridge.

The Attack: This plant can grow up to 25 feet long and form very dense mats, this allows the plant to completely plug waterways and cause havoc to boat movement and fish populations. Locally this plant can establish itself in our 2700 hot springs and cause problems with the natives. It is transported by the fragments getting onto boats, fisherman gear, or wildlife.

The Defense: Clean – Drain – Dry all equipment to ensure that this plant is not spread around. If you currently have it in your aquarium, please remove it and set it out to completely dry and then compost into your garden and landscape. The plant can be completely controlled if the water and soil dry up for two weeks. Diquat and Floridone are two herbicides that work well in slow moving water (non-irrigation).


PLEASE NOTE – The proper use and application of herbicides can be an effective way to control and eradicate noxious and invasive plants. Before using herbicides, always carefully follow the label and safety instructions on the label. While we recommend the use of herbicides as one of the effective tools for integrated pest management, the Idaho Weed Awareness Campaign assumes no liability for herbicide applications.