Invasive SpeciesJapanese knotweed

Fallopia japonica
FOUND by JessicaJonovski
2012-12-13
Portland
ID Confirmed
Quality checked by LB MW
Peer reviewed by
Field Notes
We found it! It's not as cold as we were expecting. The plant didn't seem as tall as we thought it would be.
Supporting Evidence
Photo of my evidence.
The stems are brown and are dried up. Seeds remain on the stem and are light brown, thin, very similar to the picture on the species card.
Photo of my evidence.
The branches are hollow, bamboo-like (with "joints") and are bare with a zig zag pattern. It's winter, so we know that the stems should be bare. No leaves are present.
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
Latitude: 
N 43.649760 °
Longitude: 
W -70.258260 °
Observation Site Information
A photo of our study site.
Habitat: 
Upland - Developed areas
Trip Information
Name:
Commercial Street
Trip date: 
Thu, 2012-12-13 09:15
Town or city: 
Portland
Type of investigation: 
Species Survey
Ecosystem: 
Upland
Watershed: 
Presumpscot

Comments

Your picture of the winter seeds is what I'd hoped to see when I went on my search. I am always looking for interesting winter pods and seeds, so naturally that was my main focus. Unfortunately (fortunately?), I didn't find the seeds, zig-zag patterned stems, or evidence of hollow, bamboo-like stems on my recent walk-about.

Thanks for making and sharing your observation! You did a good job focusing in on the important characteristics of this common invader. Too bad the digging last winter didn't do more...

I just did a little googling and found this from the Northwoods Cooperative Weed Management Area in Wisconsin (dnr.wi.gov/topic/invasives/.../japanese_knotweed_control.pdf):

"Cutting the knotweed only removes the aboveground portion and only serves to stimulate the below ground rhizome. In some cases weekly mowing can eventually draw down enough of the plant’s reserves to kill it."

It doesn't mention the impact of digging... Worth an experiment?

gbh

Is it possible that last winter's effort may have stimulated more dense growth? This plant gets top honors for persistence and resiliency.

Excellent photo of the seeds.