In 2011, the City’s Watershed Protection Department and Parks and Recreation Department began removing non-native invasive Arundo donaxalong Lady Bird Lake and lower Barton Creek.

WHAT IS IT?

Arundo donax (common name giant reed) is a member of the grass family that grows up to 20 ft tall, with dense compact roots that penetrate deeply into the soil. Flowers are 1-2 ft long plumes appearing in  August and September.

WHAT PROBLEMS DOES IT CAUSE?

The plant creates dense stands that choke lake shorelines and stream channels, limiting human access, interfering with flood control and increasing fire potential. It spreads quickly by fragments and root-like rhizomes, developing into a monoculture that replaces native plants (using up to 3 times the water), and reduces wildlife habitat.

WHERE IS IT ON LADY BIRD LAKE?

The City partnered with Lady Bird Johnson Wildflower Center to have their Citizen Scientist volunteers help map the plant locations on the lake.  Arundois spread along the entire 5 miles of shoreline, covering approximately 3.5 acres or 7900 linear feet. Patches range from single plants to 150 ft of dense growth.  The plants grow between the water’s edge and the hike and bike trail, usually on fairly steep slopes.

WHAT IS BEING DONE ABOUT IT?

In 2011, the City’s Watershed Protection Department and Parks and Recreation Department began removing Arundo along Lady Bird Lake and lower Barton Creek.  

The removal plan, developed with input from national and state invasive control experts, involves cutting the plants to reduce biomass, followed by herbicide treatment during plant re-growth. Spraying this re-growth rather than the mature stand minimizes the amount of herbicide used. Eradication requires aggressive initial treatment, with follow-up in the spring on any new growth.  The cutting began on August 15 and was completed September 23.

Application of EPA-approved herbicide labeled for aquatic use will begin in October on the re-growth, using a licensed private contractor who specializes in such work, with TDA Commercial Pesticide Applicator license numbers  # 0221511 and  # 0123941.

While a mixture of imazamox (trade name Clearcast) and glyphosphate (trade name Aquamaster) will be used in one area of pure Arundomonoculture, imazamox alone will be used for the majority of the treatment because it is very selective and will not impact nearby trees or undergrowth.  These particular herbicides were chosen to maximize Arundocontrol while still protecting the lake and nearby vegetation, and are suitable from both public health and environmental standpoints.