draft

Our creeks and lakes are home to an amazing number of trees, birds, fish, and other wildlife. 

Whether plants are underneath the water, floating on the surface, or growing along the banks, they play a key role in supporting this environment. Plants provide food as well as places to hide, hunt, and spawn. They contribute to improved water quality conditions. 

Watershed Protection helps monitor plant life along our lakes. We encourage native plants and try to manage invasive plants that disrupt the food web.

Lake Austin, Lady Bird Lake, and Lake Walter E. Long are man-made reservoirs, which means they function differently than a "natural" lake. Invasive plants can hinder these lakes from functioning properly.

Elephant Ear

Elephant ear (Colocasia esculenta) is not native to central Texas. It is from the Asian tropics. It has been in Central Texas since at least 1929. On Lady Bird Lake, it is especially common on the north shore, where it gets lots of sun. It likes to keep its feet wet right at the water’s edge. It can grow so densely that it prevents other plants from getting established. This reduces the diversity and resilience of the shoreline habitat and impacts large water birds such as herons and egrets.

The shallow roots of small elephant ear plants are easily uprooted in floods. This helps it spread downstream and start new colonies. 

Photo showing person in uniform removing elephant ear. 

Rather than trying to eradicate elephant ear altogether, we try to manage the population so that elephant ear does not dominate the shoreline. In partnership with American Youthworks and the Trail Conservancy, we have removed the large patches of elephant ear and planted native grasses, sedges and wildflowers in its place. We sometimes treat elephant ear with an EPA-approved herbicide.

Eurasian Watermilfoil

Eurasian watermilfoil (Myriophyllum spicatum) is also a non-native aquatic plant that is commonly found in both Lake Austin and Lady Bird Lake. In both lakes the plant tends to be most dense in the upper reaches, where water temperatures are cooler. This aquatic plant is native to eastern Europe and Asia but has been in the Austin region for over five decades. Like hydrilla, milfoil can rapidly spread by fragmentation and can form dense rafts where conditions are suitable. Treatment and removal procedures and considerations are the same as with hydrilla. Please see the recommendations for hydrilla on this page.

The Austin-region does also support a native milfoil, Parrot’s feather (Myriophyllum aquaticum), but it’s distribution and growth are very limited in the lakes.

Fanwort in Lady Bird Lake

Fanwort (Cabomba caroliniana) is a native aquatic plant that grows in Lady Bird Lake. It has delicate white flowers that often bloom underwater. Fanwort provides oxygen, food and hiding places for fish, turtle, birds, and other aquatic life. It helps filter pollutants from the water and may prevent other, less desirable vegetation from spreading in the lake.

Because fanwort can spread quickly over large areas of the lake, it is disliked by some recreational users. However, we generally avoid actively managing the plant since it is beneficial for aquatic life and has a natural life cycle. The plant tends to be uprooted and dispersed by large flow events after large storms.

Austin residents and business owners along the lake may get a free permit from Texas Parks and Wildlife to remove nuisance vegetation from around their docks.

Giant Reed

Giant reed (Arundo donax) is a member of the grass family that grows up to 20 feet tall, with deep, dense roots. Flowers are long plumes, one to two feet long, and appear in August and September. Giant reed spreads quickly by fragments and roots.  

Photo showing blooms of Giant Reed

It can form dense stands along the shoreline of Lady Bird Lake and along creek channels. It can choke out other plants, limit access to the lake, interfere with flood control and increase fire potential.

In the past, before years-long removal efforts, giant reed was most abundant near Red Bud Isle, the mouths of Barton and Waller Creeks, and downstream of IH-35. It grew on steep slopes between the lake and the Ann and Roy Butler Hike and Bike Trail. However, stands of the plant can be found along numerous creeks as well as Lake Austin’s shorelines.

Removal is challenging. Elimination includes cutting the plants down and then treating them with a herbicide. Sometimes, we needed to re-treat a single stand for multiple years. Following removal of a stand, we have worked with the Trail Conservancy to restore the area impacted and encouraged native plants. 

Hydrilla in Lake Austin

Hydrilla (Hydrilla verticillata) is a non-native aquatic plant that was first observed in Lake Austin in 1999 and has shown the ability to rapidly grow and spread. It has negatively impacted water intakes, recreation, and navigation on the lake.  However, like all aquatic plants, hydrilla does provide valuable water quality benefits and support of the aquatic food web.

The City of Austin, Texas Parks and Wildlife Department, Lower Colorado River Authority, and Friends of Lake Austin have worked together to control hydrilla through the use of sterile triploid grass carp as well as drawing down the lake in the winter.

To help prevent its spread, you should:

  • Avoid boating through dense hydrilla mats.
  • Remove hydrilla from your boat's propeller and trailer before and after boating.
  • Dispose of all plant fragments on shore. Be aware that new plants can grow from just a fragment of a plant.

If you are removing hydrilla from the lake, follow these guidelines:

  • Plants should be placed as far up on the shore as possible.
  • Plant material stockpiled within 75 feet of the water's edge should be surrounded on the downslope side by silt fencing.
  • Plant material pulled from the lake will contain small fish and other organisms and will have an odor associated with it. The plants are mostly water, and piles will lose 90% of their bulk within two to four weeks. This material can be used to mulch flowerbeds or gardens.

Throwing hydrilla back in the lake can result in a maximum fine of $2,000 per plant.

Habitat Restoration on Lake Austin 

Changes to plant life can have a negative impact on the food web. Loss of habitat can occur through removal of vegetation, growth of invasive species, or natural causes such as storms

We have tried different ways to restore habitat in Lake Austin. In coordination with the University of North Texas, we established founder colonies of aquatic vegetation within temporary cages. Cages protect the desired vegetation from ducks, turtles, grass carp, and other plant-eaters. The hope was that caged plants will spread naturally throughout the lake. However, after years of effort, we have observed that the rapid growth rates of non-native hydrilla and Eurasian watermilfoil tend to exceed those of native vegetation.

Together with Texas Parks and Wildlife, the Texas Tournament Zone and volunteers, we have also sunk evergreen trees into deep water. This imitates the natural process when trees along the shoreline die. The trees stimulate the entire food web. First, bacteria begin to grow along the green tree leaves. The bacteria, in turn, become food for invertebrates and small grazing fish. Fish, both small and large, live among the submerged tree branches, hiding and hunting each other. Essentially, the tree becomes a buffet line for all the residents of the lake!

Research and Publications 

For more articles, visit our publications database. 

You can help!