Water Willow – When a Native Plant Becomes a Nuisance Plant

Mon, August 24, 2015 | Lakes and Parks

If you visit Loch Lomond in Bella Vista Village, especially the lower end of the lake near the dam, you’ll notice extensive beds of very green, lush, plants growing in shallow water along the shoreline. The plant is water willow, Justicia americana, a native plant that grows throughout the southeastern and northeastern U.S. 

The plant was found sparsely in the lower end of Lomond when I started here in 2008, seemingly having just found its way to the lake just prior.  I assume the plant found its way to Lomond by natural plant dispersion means, but I don’t know for sure. The plant is still not found in several village lakes, but it has found its way to Lakes Norwood and Brittany, and perhaps others. 

Now, in Lomond, the plant has been spreading rapidly and seemed to increase and expand its growth during the lake drawdown in 2008-09.  For the last few years a couple residents on Lomond each year complained of the weed taking over their lake-front areas. This year, the list has become very long.

Overall, the plant is very good for the lake and exhibits some very positive influence on the lake. It provides shoreline protection from erosion from wave action and it provides excellent fish habitat, especially for young fish. This habitat is very beneficial as a “nursery” for increased survival of young forage fish such as bluegill, while also providing protective cover and ambush habitat for predator fish such as largemouth bass. Also, many lake front residents feel it provides as nice aesthetic for the lake also. 

But this is another case, as is so common in life, of too much of a good thing.  Now this aquatic plant has spread into shoreline areas where it has completely or significantly impacted the lake use by shoreline residents, growing along their docks and seawalls. These are the folks that have called me asking for some help. It also is negatively impacting our POA facilities in some cases, such as the marina, where it blocks access to the rental kayak dock and fishing along the shoreline. 

Through experimentation over the last few years, we have figured out that the only really effective way to control this plant is through chemical control using direct application of a restricted herbicide onto the plants. The systemic herbicide moves throughout the plants and rhizomes (runners in the lake substrate) and kills the plants. Our policy is that we do not want to eliminate the plant from the lake but rather control its growth to areas where it does not negatively impact shoreline residents or POA facilities. We want to leave it and allow it to exist in other areas because of the positives mentioned earlier.

As with many issues in lake management here in the village, manpower is what is limiting our ability to focus on this issue to manage the situation.  But we have scheduled late August and September to focus our efforts on this. We will likely have to spend several weeks each summer on water willow control, each year, among the lakes where it is present. If we can’t field a crew with our equipment, we will have to budget for bringing in an outside contractor. We will have a harder time with precise control location with if we rely on an outside contractor to spray herbicide.

This week, we began by mapping the weed beds in each lake using a GPS unit working from a boat out on each lake. This allows us to create a GIS map database on the computer and we can re-map each year to track the changes in weed distribution due expansion and our control measures. This will give us the ability to create visual maps to help discuss the problem and justify the associated budget / manpower needs to work on the issue. Next week, we will start herbicide application working around other monthly scheduled activities.

Figure 1.  Full-time bio-technician, John Urquhart (driving boat) and part-time bio-technician Chris Fuller (operating hand-held GPS unit) mapping location and distribution of water willow on Loch Lomond, August 20, 2015.

 
Lake Draw-down Schedule and Management

Overtime, we have received more and more calls regarding lake draw-down schedule, mainly from shoreline residents that need or desire to conduct new or renovation work on docks and/or seawalls. It’s important that members understand our current schedule and policy. 

Due to the intensity of POA work and costs associated with lake draw-down, we can only conduct draw-down on one lake per year at best.  We will only conduct a draw-down on a lake if a very pressing need exists regarding POA facilities or the lake itself. Therefore, we have put the seven lakes on a seven year rotation to be considered for draw-down for the purposes of budget planning. We have basically run through one cycle following this plan beginning with Lake Avalon back in 2005-06, and followed by Lomond in 2008-09, Windsor in 2010-11. Ann in 2011-12. We skipped the 2009-10 season. We also did not conduct draw-downs on lakes Brittany, Norwood, and Rayburn during the past few seasons.

All these draw-down’s were driven by POA facility / common property / lake need. Avalon drawdown was needed for sediment removal and other work in the extreme upper end of the lake relating to bacterial contamination and sediment accumulation in that area. Lomond drawdown was conducted to remove accumulated sediment in the extreme upper end of the Tiree arm of the lake. Windsor drawdown was conducted for sediment removal in the extreme upper end of both main arms of the lake, and POA facilities maintenance needs, especially dock and seawall replacement construction at Windsor Park and Windsor Dam. Lake Ann drawdown was conducted the following year to remove accumulated sediment from the main arm of the lake and to replace the POA boat ramp.  Sediment removal is needed in the upper end of Lakes Norwood, Brittany, and Rayburn, however, POA has no or very limited access to those areas.
 
So now, we’ve started over through the cycle again. The following lists the current order of lakes to be considered for draw-down in this, seven year rotation:



































 LakeBudget year consideration Draw-down implementation
 Avalon 2014 Nov. 2015 – March 2016
 Lomond 2015 Nov. 2016 – March 2017
 Windsor 2016 Nov. 2017 – March 2018
 Ann 2017 Nov. 2018 – March 2019
 Rayburn 2018 Nov. 2019 – March 2020
 Norwood  2019 Nov. 2020 – March 2021
 Brittany 2020 Nov. 2021 – March 2022

To be clear, the rotation is to consider a lake for draw-down, not to conduct a draw-down for sure. We, the POA management, work on a calendar year budget and that budget has to be set-up and approved the prior year. Therefore, we will evaluate the need for draw-down during the budget year prior to scheduled draw-down. If we cannot justify the need for draw-down based on POA facility / common property / lake needs, we will not conduct the draw-down, and that lake will not be considered for another seven years, barring emergency, or change of plans by POA Board of Directors or management. 

In following this rotation plan, last year an evaluation of Lake Avalon did not justify the need for draw-down this year, therefore is was not budgeted and will not be conducted. This year an evaluation of Lomond revealed a lack of need to draw-down Lomond and therefore, the current draft budget for 2016 does not contain funds to conduct a draw-down on Lomond in 2016. Next year, we will consider Lake Windsor for draw-down in 2017. 

It is also important to note that only Lomond Dam was built to accommodate draw-down as it is the only dam that with draw-down gates originally built in the spillway. We modified Windsor dam with the exact same array of draw-down gates to facilitate the draw-down in 2011-12, at a cost of a couple hundred-thousand dollars. Ann Dam was retrofitted with two siphon-tubes after original construction, providing a draw-down mechanism on that lake. Lake Rayburn is the only lake that uses a standpipe style spillway tower in combination with an emergency spillway. The standpipe spillway might accommodate lake draw-down if a draw-down becomes possible at Lake Rayburn.  Dams at Lakes, Avalon, Brittany, and Norwood, have no draw-down mechanism built into the existing dams and spillways. Retro-fit construction of a draw-down structure in these dams should be conducted in conjunction with scheduled draw-down if implemented next time. 

Figure 1.  Opening draw-down gates in Loch Lomond Dam, November 2008.

 
Figure 2.   Retrofitting draw-down gates in Lake Windsor Dam spillway in 2010.

If you visit Loch Lomond in Bella Vista Village, especially the lower end of the lake near the dam, you’ll notice extensive beds of very green, lush, plants growing in shallow water along the shoreline. The plant is water willow, Justicia americana, a native plant that grows throughout the southeastern and northeastern U.S. If you visit Loch Lomond in Bella Vista Village, especially the lower end of the lake near the dam, you’ll notice extensive beds of very green, lush, plants growing in shallow water along the shoreline. The plant is water willow, Justicia americana, a native plant that grows throughout the southeastern and northeastern U.S.