Alligator weed: Kudzu of the Waterways
Alligator weed (Alternanthera philixeroides) is an invasive exotic menace. It was first introduced to this country about a hundred years ago from South America in ballast water from ships. Many exotic species have spread this way.
This perennial is generally an emergent or rooted floating plant, but it can invade adjoining uplands throughout the southern portions of the United States. It has become a common terrestrial weed here.
Plants have hollow stems and can grow to 3 feet tall. Opposite, elliptical leaves are thick but non-succulent and are up to 4 inches long. Plants flower in summer with white, miniature clover-like heads at the leaf bases.
When alligator weed spreads it slows water flow. This clogs our ditches, displaces native vegetation, restricts oxygen levels of water, increases sedimentation, interferes with irrigation and prevents drainage. When plants die, decomposition lowers the free oxygen in the water and endangers many types of aquatic life.
Another problem is that by slowing down water movement, it is responsible for an increase in mosquito populations. Mosquitoes prefer shallow stagnant pools and alligator weed facilitates that.
Several chemicals are labeled to control alligator weed, but applying anything to our water can raise red flags. Concerns about water contamination can be real, especially immediately after treatment. Only trained and certified applicators should ever apply pesticides to aquatic areas.
There are other solutions. An insect called the alligator weed flea beetle, (Agasticles hygrophila), is quite effective at controlling this weed. More importantly, the insect is quite specific in its appetite for alligator weed.
The alligator weed stem borer and the alligator weed thrips also help stifle this pest. The thrips (distant cousins to the irritants that inhabit our wheat fields in late spring) are the only critters that effectively control terrestrial alligator weed.
Does it have any uses? It makes a suitable aquarium plant, and yes, you can eat it. It is readily available in spring, summer, and fall. Mineral and protein content are high, though some essential amino acids are limited compared to meat proteins. Taste is not objectionable, either. That is provided you didn’t harvest it from some stagnant mud hole.
When eaten raw the taste is improved with salt and some type of dressing. When cooked it also benefits from a little salt and butter or pork fat. Many palates prefer some vinegar, but I don’t like it on my cooked greens.
Alligator weed would not be near the top of my list simply because of where it grows and the potential problems that could arise. As mentioned earlier, it accumulates high levels of minerals. It also accumulates heavy metals readily if they are present, so contaminated waters could pose major problems.
I look upon alligator weed strictly as a survival food, and not a sought after delicacy like some I’ve profiled. The downside far exceeds the upside, and we would be fortunate if we could eradicate this foreigner from our landscape. It’s the nutria of the plant world, but it does taste better than cattail, so I guess that’s a start.
Ted Manzer teaches agriculture at Northeastern High School.