By Susan and Biff Andrews

We have written in this space before about many non-native invasive species that threaten to harm — and are harming — our local ecology. They are legion.

Tree of Heaven, Japanese stilt grass, snakeheads, rapa whelks, blue catfish, brown marmorated stink bugs, fire ants….

Today we’re going to warn, describe and complain about another such species. It was introduced into the U.S. in 1894 in ballast water from ships arriving from South America — unlike the starlings from Europe, Asian snakeheads and stilt grass and so on.

Alligator grass. It is spreading worldwide at an alarming rate. In Australia, it’s considered such a threat that if you even see some, you are bound by law to call and report it, and the government will send an eradication team to get rid of it.

How it got into Lake Meade we don’t know, but it is rapidly taking over. Portsmouth water supply folks would do well to listen up before it spreads any further.

First, a description.

Alligator grass forms dense mats on top of water (and nearby land), which have several deleterious effects. It has hollow stems, leaves that are opposite in position, and white fluffy flowers on stalks up to two inches long.

The mats of weed are about a foot thick and spread very rapidly. Some mats float free and drift up and down our lake, like floating islands. Some can root in water and stay put. Some can root on land, as we discovered when we whacked some in front of our dock and put it in our mulch pile, where it grew all summer quite happily.

If you see a shoreline on fresh water that is choked with weed out 30 feet, it’s probably alligator grass.

It has several harmful effects on the local flora and fauna. It crowds out native plants, as it spreads like wildfire.

It lowers the oxygen and light levels for native fish. When it dies back in winter, it forms a dense sludge on the bottom where nothing can live or grow. It inhibits the use of the shoreline. We can barely get our jonboat into our dock.

And the surface area of the lake is shrinking rapidly, which the Portsmouth water folks may wish to consider.

People are looking for ways to turn a negative into a positive, as with kudzu. They are trying to use it as biomass for energy production (as with kudzu), since a given area can be “harvested” every 45 days and never run out.

They’re trying to conveyor-belt it out of lakes. It’s not really working.

The only way to kill alligator grass is with herbicides — glyphosate when it is in water, Brush-off when it is on land. Control of these substances is limited, and glyphosate costs $125 a gallon if you wanted to get the permission to use it.

The lake behind our house is shrinking rapidly as the stuff spreads. It’s only a matter of time until it’s in the other water supply lakes in Suffolk.

Given the current reluctance to spend any tax dollars on any form of infrastructure, I’m sure nothing will be done about our water supply until we have a crisis with lots of hand-wringing.

Oh, well. Maybe we should move to Australia.

Susan and Bradford “Biff” Andrews are retired teachers and master naturalists who have been outdoor people all their lives, exploring and enjoying the woods, swamps, rivers and beaches throughout the region for many years. Email them at b.andrews22@live.com.