Invasive SpeciesJapanese knotweed

Fallopia japonica
FOUND by 41sg71
Waterboro, Maine
ID Questioned
Quality checked by pparent
Peer reviewed by 41sg7
Field Notes
On May 5th, my Japanese knotweed investigation took place. It was around 3:00pm and the weather was sunny, and the temperature was at about 60º fahrenheit. I was not sure of the exact humidity. While I was looking around on the side of the street, I spotted the Japanese knotweed. I think that it is this invasive species because of the similar characteristics it carries. The Japanese knotweed’s characteristics are in the following sentences. It’s stem is jointed, just like the plant that I found, and is wooden and about 2 cm thick. When I found the plants, they were about 1 meter high, and were light brown and went into red as the stem led into the leaves. The leaves were approx. 20 cm wide, and 28 cm long. They were alternately arranged, with a very wide shape. I definitely believe that it is Japanese knotweed, because of the exact characteristics. There is a predator of this invasive species, but it is in Asia. There were no insects on these plants as I looked. Here are the classification characteristics of Fallopia japonica(Japanese knotweed): Kingdom: Plantae (unranked): Angiosperms (unranked): Eudicots (unranked): Core eudicots Order: Caryophyllales Family: Polygonaceae Genus: Fallopia Species: F. japonica
A sketch of our study site.
Supporting Evidence
Photo of my evidence.
The leaves are widely-shaped, and are curved on the sides. They are also light green. Those are two similar characteristics of the Japanese knotweed invasive species plant.
Photo of my evidence.
The leaves also have an alternate leaf arrangement, like the Japanese knotweed plant. The leaves on Japanese knotweed do not seem whorled OR opposite, and definitely seem alternate, as shown in the image.
Photo of my evidence.
The stem is a greenish color, which it usually is. It is jointed, so it isn't necessarily straight. It goes into a red tint near the leaf attachments. These are the same characteristics of the stem as Japanese knotweed.
Species Observation: Species Looked For
Did you find it?: 
I think I found it
Scientific name:
Fallopia japonica
Common name:
Japanese knotweed
Sampling method: 
Just looking around
Photo of our sampling method.
Place Studied
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Map this species
N 43.571165 °
W -70.677108 °
Observation Site Information
A photo of our study site.
Upland - Developed areas
Trip Information
Waterboro, ME
Trip date: 
Sat, 2012-05-19 15:00
Town or city: 
Waterboro, Maine
Type of investigation: 
Species Survey


Hi 41sg71,

The leaf size that you reported is really large. I'm suspicious that this might be Fallopia sachalinensis, not Fallopia japonica.

The best way to tell is to go back to your plant and examine (and photograph) the underside of the leaves. Look closely to see if any small hairs are visible, especially around the ribs of the leaf.

Please leave me a comment to let me know what you discover. Then I'll be able to confirm or question your identification.

Thanks for this interesting posting!

...but these leaves aren't heart-shaped. They have a very flat base at the end attached to the stem. I think that's a good indicator that this is Japanese knotweed and not giant knotweed.

Nice sketch!! I just recommended you for the best of VS page!