Invasive SpeciesJapanese knotweed

Fallopia japonica
FOUND by tkmeyer
ID Confirmed
Quality checked by Me
Peer reviewed by
Field Notes
It's midmorning and overcast. Although there's an occasional slight breeze, the air is heavy. The bugs are out and biting! Thunderstorms are forecasted for today. All this rain has made my backyard grass grow another 3 inches and these tall, dense stalks overtake my backyard. I have to mow my lawn every week. And these thick stalks, I cut them back, but they come back with a vengeance! These resilient stalks are what I'm identifying today.
A sketch of our study site.
Supporting Evidence
Photo of my evidence.
Japanese Knotweed grows in a dense bush. It also has noticeable joints along its stem, like bamboo. This picture shows the compact stems. Along each stem, you can see the visible joints. Characteristic of Knotweed is its distinctive purple specks. If you look closely, you can see these specks in the picture.
Photo of my evidence.
The leaves of the Japanese Knotweed are elongated, simple, oval, and spade shaped with an abrupt narrow tip and a smooth edge. The leaves also alternate on zig zags stems. Here, in the middle of the picture, you can see the leaves growing from the points of the zig zags. Measuring a few leaves, the largest one was about 15 cm long (measured along the center of the leaf from the bottom to its tip), and 9.5 cm at its widest. This could not be the similar species, the Giant Knotweed, which has elongated heart shaped leaves that are typically 15 cm to 40 cm long.
Photo of my evidence.
Japanese Knotweed also has hollow stems. This picture shows one of the stems cut open. You can clearly see that there's nothing inside of the stem! Also, if you look along the stem, you can also see the distinctive purple specks of 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 44.887142 °
W -68.659663 °
Observation Site Information
A photo of our study site.
Upland - Developed areas
Trip Information
My Backyard
Trip date: 
Wed, 2013-06-26 10:00
Town or city: 
Type of investigation: 
Species Survey


I love your sketch!

You really captured both the shape of the leaf and the zigs and zags of the stem of F. japonica! Oh, how lovely it is. Thank you for sharing your deft observation and drawing hand. I'm going to nominate you for a best of sketch.

AND I love your dachshund just looking around in your method picture... hehe.

This species threatens to invade my yard. I'm fighting an endless battle. There is an undisturbed clump on my neighbor's property and it persists in sending rhizomes into my yard. To some extent, I've trained it to stay away by pulling any shoots I see. I want it to think it has nothing to gain by growing on my side of the property line. Oh how we humans love to anthropomorphize!

All that aside, this is a really excellent observation. Clear, well presented evidence with crisply focused images. Great stuff. Thank you for reporting your observation!


TKMeyer, that's an awesome observation! Great job. Everything about it is fantastic. I, personally, love the picture of your super adorable dog. Because we love your observation so much, you can now find it uploaded as a Best Observation ( and under the Best Sketches ( page. Your sketch is extremely precise and detailed. Nice job there, too. I also love the clear picture of the hollow stem.

Great job! I hope you keep uploading observations.


Thank you! This was my first observation, and I had fun despite the multiple bug bites. I didn't have to go far for my field trip, but I'm excited thinking about all the different places to explore in ME and the new observations to make.

My two dachshunds LOVE navigating through the Japanese Knotweed. The other one isn't in the picture -- he's lost in the stalks somewhere.