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. 

Austin 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, invasive plant that was first observed in Lake Austin in 1999. We have learned much since that time about the challenges of managing this plant. 

Current status

October 3, 2025: There has been a spike in hydrilla's extent in Lake Austin since June. The plant is now covering approximately 30% of the lake, up from less than 5%  in June.

Texas Parks and Wildlife conducted a survey of vegetation in the lake in September. They found 313 acres of hydrilla and another 286 acres with a mix of hydrilla and Eurasian watermilfoil. Combined, this makes for an estimated 456 acres of hydrilla. The amount of hydrilla is approaching its peak of over 500 acres in 2012 and 2013.

Because we are at the end of the typical growing season, we expect the growth of hydrilla to slow down on its own over the winter. This gives us some time to respond and try to reduce the amount of hydrilla and further slow its growth rate.  To do this, we are arranging to add more sterile grass carp later this fall.

Grass carp prefer to eat hydrilla and are the most environmentally responsible tool available to manage the plant. We are planning to maintain the recommended stocking rate of five grass carp per acre of hydrilla. This is to help reduce hydrilla while minimizing the grass carp’s impact on native vegetation. 

Aquatic vegetation can benefit fish and water quality

In reasonable quantities, hydrilla shares some benefits with other aquatic vegetation:

  • It provides oxygen for fish and other aquatic life
  • It creates hiding places and forage areas for fish
  • It uses up excess nutrients and absorbs other pollutants

Hydrilla can grow rapidly

From 1999 to 2003, hydrilla was able to cover about an eighth of the lake. We have seen an even more rapid spread since June. Once hydrilla covers large areas of the lake, it can cause problems for both the environment and our community. Hydrilla may form dense mats that can clog waterways and lead to flooding. Dense mats of hydrilla can also impede boats. Hydrilla can out-compete our native vegetation.

A balancing act

Managing hydrilla with sterile grass carp is a complicated balancing act that takes time. Grass carp generally live for 10 to 20 years, but some may live longer. They prefer to eat hydrilla over other vegetation.

On one hand, it takes time for them to eat enough hydrilla to have a visible impact. On the other hand, there needs to be enough food for them for their whole lifecycle. We do not expect to see immediate reductions in the amount of hydrilla after the grass carp are stocked. However, we expect to make sustained progress on managing hydrilla over time.

Past experience shows that environmental conditions can also have a significant impact on the spread of hydrilla. Droughts create conditions favorable to hydrilla. During the drought from 2010 to 2013, it seemed like we couldn’t stock enough grass carp to keep hydrilla under control. But once the drought ended, the grass carp were still around. Beginning around 2014, all aquatic vegetation began disappearing from the lake, eaten by hungry grass carp. It has taken about 10 years for the lake to recover and reach target levels of aquatic vegetation.

Environmental factors may have contributed to the rapid spread of hydrilla this summer. We think it may be a combination of flooding and drought. The July floods may have brought in more sediments and nutrients. But, since the floodwaters were stored in upstream lakes, flows through Lake Austin were not fast enough to uproot the hydrilla as previous floods have done. The added nutrients from the July floods may have combined with warm waters and low flows to create the perfect growing conditions for hydrilla. Rain from a number of smaller storms may also have washed fertilizers from shoreline lawns into the lake. 

Many Lake Austin community members have expressed interest in temporarily lowering the level of the lake to help reduce the amount of hydrilla. While lowering the lake has been effective at controlling Eurasian watermilfoil, data suggests that it is not effective at controlling hydrilla. In fact, lowering the lake might encourage the spread of hydrilla. That’s because it would eliminate less problematic aquatic species, which might allow hydrilla to spread more aggressively. Lowering the lake could be useful for the maintenance of structures along the shoreline. 

Past experiences underlines the importance of proceeding with caution and giving the lake environment time to adjust to changing conditions. Our goal is to avoid harming wildlife habitat or water quality to ensure a healthy lake for the environment and the community.

Help Prevent the Spread of Invasive Species

To help prevent the spread of non-native species like hydrilla and zebra mussels, you should:

  • Clean, drain, and dry your boat and gear before and after use
  • Avoid swimming and boating through dense patches of underwater vegetation
  • Don’t toss plant pieces back into the lake – State fines can be up to $2,000 per plant

Properties along the Lake

Fertilizers used on lawns and gardens may be washed into the lake when it rains and contribute to the growth of hydrilla. Consider reducing the use of fertilizers on lawns. In addition, creating a landscaped area with native and adapted plants along the shoreline may help. The plants act as a buffer and help prevent nutrients and other pollutants from entering the lake.

If you are struggling with hydrilla near your property, consider hiring a contractor to clear the hydrilla around docks. The contractor should have a permit from the Texas Parks and Wildlife Department to perform this work.

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. 

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