Why So Much? (invasive species)

I’ve been noticing a lot of Japanese stilt-grass in my area recently, like a lot. It got me wondering what effects Japanese stilt-grass, and other invasive species, have on the native species in my area. I’m also curious to know what other effects it may have on the environment. If anyone has some answers please share!

*Also please let me know of some interesting projects, I’d love to join them

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What area are you in?


I’m in Massachusetts.

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stiltgrass, like most invasive plants, thrives in disturbance, near roadsides and houses, and the climates of eastern north america and east asia are pretty similar, hence why a lot of notable invasives in the eastern US are from there (Ailanthus, japanese honeysuckle, multiflora rose, porcelainberry, barberry, wineberry, Tenodera mantises, lanternflies, brown stinkbugs, list goes on)


See https://extension.psu.edu/japanese-stiltgrass and https://www.lewisginter.org/japanese-stiltgrass/ for a brief description.
If it forms a dense monoculture in an area, it will crowd out other ground level vegetation which will likely displace a number native species. The reduction of native species abundance and diversity will put pressure on any specialist animals that rely on those species. Many butterflies/moths, bees, and other arthropods (even grasshoppers) depend on a specific plant (or small group of closely related plants) at some stage in their lifecycle. If these species experience dramatic population declines it can have ecological ripple effects, especially if there are not other species ready and able to fill the void as food for other creatures, pollinators, or seed dispersal avenues, etc.
For example, if certain butterflies and moth populations crash because the plants that their caterpillars rely on are no longer available and other butterfly/moth species do not proportionally increase their populations in response to less competition, then many songbird populations could also decline if they cannot find enough caterpillars to raise healthy chicks during their breeding seasons. Over time, fewer songbirds might lead to fewer raptors and poorer seed dispersal for other plants not directly impacted by the Stilt Grass. Poor seed dispersal for those plants could reduce or concentrate populations in such a way that will have some other ecological impact, and so on. There are also a host of impacts that could occur below ground with soil texture, microbial activity, water infiltration/retention that can have wide ranging effects.
Also, if an animal’s normal food source is disrupted, it may be forced to venture farther afield outside of natural areas (forests and such) and into human populated areas such as deer devouring backyard gardens rather than feeding in the forest (admittedly, in many places, this particular example is often caused by over population rather than a lack of forage).
While some species might benefit from changes spurred on by invasives, others certainly will not. It is somewhat misleading to speak of natural equilibrium in an undisturbed native ecosystem because all of the living organisms in ecosystems are in a constant state of change and adaption. However, the introduction and aggressive spread of invasive species often throws out the rules by which an ecosystem changes leading to more disruptive change over a very short period of time (e.g. years or decades as opposed to centuries).


Please learn how to eradicate it, it will eventually form a thick mat of leaves that will choke everything else out. It’s an annual so it is best to cut down before it goes to seed.


I’m surprised more people don’t talk about stiltgrass. It’s arguably worse than the other big bads like knotweed because it spreads much faster and as far as we know has no biological control. You have to manually pull it out which is near impossible in the large wooded areas it infests, and even a single left over plant will make thousands of seeds for the next year.
The only good thing about the drought we’re having right now here is that it killed most of the stiltgrass in my backyard.

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It is a grass and if you’ve been noticing it, it must have established. Eradication is futile in my opinion. Try to think in another way, such as it is a green plant that absorb CO2. Invasive species spread due to globalisation and also because of a natural process of a species simply spreading by the usual ways of seeds carried by wind. Exotic weeds can be in potted plants due to global trade. or maybe on the side of shoes or bags of travellers. Maybe some soldiers stationed in Japan and moved back to USA, there is some mud in the boots with some seeds. Various possible reasons.

Apparently japanese stilt-grass is one of the hosts to an endangered butterfly, the Mitchell’s satyr. So pulling it out in forests isn’t really recommended - eggs and caterpillars of the endangered species could be on the plant.

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But its range is not in Massachusett’s, so I don’t think that is a concern here.
And there is probably a time when you can remove it and replace with the Mitchell’s Satyr’s original host plants without impacting the organism.


Hi all! I recently looked into my town’s use of herbicides to control invasive species – namely Japanese knotweed, Purple loosestrife, Oriental bittersweet, Norway maple, etc etc throughout the most used path that stretches across a wide berth of the town. Actively, I’m trying to take data across the Brook Path to see how these herbicides have affected biodiversity in the region, compared to the biodiversity in a sanctuary. Any thoughts on potential outcomes/ways to effectively take data? Id love to hear from you!

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I see Japanese stilt-grass all over the forest here in Ohio. And I think right now is when it is growing in height a lot - I found a small green wood orchid last week with its flowering stem visible above the sea of stilt grass still, yesterday tried to show it to someone but the stilt grass had grown much higher and it was impossible to find anything between the millions of stilt grass plants. (If stilt grass is not supposed to grow higher right now my GPS could also have been off, but I’m pretty sure it was the stilt grass growing higher.)

My hope is that some plants (like the orchid above) which do have leaves several weeks earlier than the stilt grass can maybe get enough sunlight earlier in the year and yet survive? I don’t know anything about how plants compete underground though, so maybe the stilt grass will still kill them off by taking all the soil nutrients?


There’s a term called allelopathy, it’s when one organism secretes a chemical which inhibits others’ growth or slows it down. It’s the case with many plants, such as walnuts or the mother-of-thousands houseplant, for example. They can produce it in their roots, and then prevent other plant species from growing near them. I don’t know if stilt grass does this, though

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It’s actual native host plant is a sedge though. We shouldn’t destroy entire ecosystems to save one butterfly that only exists in like 3 states.

my town’s use of herbicides to control invasive species – namely Japanese knotweed, Purple loosestrife, Oriental bittersweet, Norway maple, etc

Herbicide is the only realistic control for Japanese knotweed, but I wouldn’t use herbicide on the other three.

Purple loosestrife has a bio-control that seems to be quite effective. My town in north-central Massachusetts was one of the release sites. It seems to have worked. Purple loosestrife isn’t gone (it never will be), but the beetle keeps it to a level where it doesn’t overrun the ecosystem. Now phragmites is taking over, but that’s another story.

Bittersweet is best just cut. For small stems, pull up the roots, and keep pulling by following the stringers along. They are quite shallow extending laterally. For large vines, cut out a section that you can easily reach from the ground. That will kill whatever is above. Then paint or do a quick spray of glyphosate on the cut stump now sticking out of the ground. This must be done quickly after cutting, preferably within a minute or two.

For Norway maple, just cut it. There will be some stump sprouts, and maybe other sprouts do to existing seeds. Pull the small ones and cut the ones coming from the old stump. Eventually the roots will be exhausted. It helps to do a quick spray of herbicide on the stump when it was originally cut.

Other then on cut stumps, you don’t need herbicide for any other species you listed except knotweed. Even then, the best first pass treatment is to cut the knotweed low to the ground just below a knot, then drip a little herbicide into the hollow stem. Unlike what others say, it doesn’t take a lot. We use just 2 ml of properly diluted Roundup Pro (glyphosate). Give that a few weeks at least, then treat the stragglers with foliar spray in the fall, about the time healthy plants would be blooming.

By the way, we (the Town of Groton Invasive Species Committee) have done some research on different treatments for knotweed. We found that very dilute triclopyr works really well as a foliar spray. Specifically, we use Garlon 4 Ultra, with a little bit of methylated seed oil added as a surfactant. Knotweed is highly susceptible to triclopyr, which is very useful if there is grass around the knotweed you want to keep. Use 1/4 strength of what the label would otherwise imply. 1/2 strength works better than full strength (relative to label recommendations), and 1/4 strength works better then 1/2 strength. I don’t know exactly why, but my guess is that triclopyr otherwise kills the leaves so fast that they don’t have time to pass on the herbicide into the roots before they die.

I know that glyphosate is usually preferred to triclopyr mostly due to the cost, but when you’re only using 1/4 the normal strength, it gets a lot cheaper. That and the higher dilution of Garlon 4 Ultra over something like Roundup Pro in the first place means the Garlon treatment is actually cheaper.


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