Japanese Knotweed - Revision history

Watlington: Added list of approaches

2025-07-15T00:33:10Z

Added list of approaches

← Older revision		Revision as of 00:33, 15 July 2025
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	Removal is EXTREMELY difficult. The roots go very deep (up to ten feet), and spread horizontally. Any small piece of rhizome will sprout and regrow.		Removal is EXTREMELY difficult. The roots go very deep (up to ten feet), and spread horizontally. Any small piece of rhizome will sprout and regrow.

	Regular cutting/mowing can slow down its growth, but will not kill it and is not recommended as it will encourage the plant to spread horizontally. Care should be taken that the mower doesn't spread the material.		Some approaches are:

	The Michigan Dept. of Natural Resources has a [https://mnfi.anr.msu.edu/invasive-species/JapaneseKnotweedBCP.pdf ~~good~~ Knotweed Best Control Practices]. They discuss how ~~herbicides~~ that ~~are~~ capable of killing Japanese Knotweed also kill any other plants and trees in the area.		* Regular cutting/mowing can slow down its growth, but will not kill it and is not recommended as it will encourage the plant to spread horizontally. Care should be taken that the mower doesn't spread the material.
			* Digging it out. This is impractical, as the rhizomes extend to far into the ground, although it is discussed as a way of weakening the plant so that chemical controls may be used.
			* Chemical controls. The Michigan Dept. of Natural Resources has a [https://mnfi.anr.msu.edu/invasive-species/JapaneseKnotweedBCP.pdf great Knotweed Best Control Practices]. They discuss how a herbicide that is capable of killing Japanese Knotweed will also kill any other plants and trees in the area. Glyphosate (Roundup) will only affect it for a year.
			* Smothering.

	The NH Dept. of Agriculture has a [https://www.agriculture.nh.gov/publications-forms/documents/japanese-knotweed-bmps.pdf Japanese Knotweed Best Management Practices] which recommends smothering it:		The NH Dept. of Agriculture has a [https://www.agriculture.nh.gov/publications-forms/documents/japanese-knotweed-bmps.pdf Japanese Knotweed Best Management Practices] which recommends smothering it:

Watlington: Added link to Michigan DNR best practices, which includes a long description of herbicides which might work (glyphosate doesn't affect it).

2025-07-15T00:08:29Z

Added link to Michigan DNR best practices, which includes a long description of herbicides which might work (glyphosate doesn't affect it).

← Older revision		Revision as of 00:08, 15 July 2025
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	Regular cutting/mowing can slow down its growth, but will not kill it and is not recommended as it will encourage the plant to spread horizontally. Care should be taken that the mower doesn't spread the material.		Regular cutting/mowing can slow down its growth, but will not kill it and is not recommended as it will encourage the plant to spread horizontally. Care should be taken that the mower doesn't spread the material.

			The Michigan Dept. of Natural Resources has a [https://mnfi.anr.msu.edu/invasive-species/JapaneseKnotweedBCP.pdf good Knotweed Best Control Practices]. They discuss how herbicides that are capable of killing Japanese Knotweed also kill any other plants and trees in the area.

	The NH Dept. of Agriculture has a [https://www.agriculture.nh.gov/publications-forms/documents/japanese-knotweed-bmps.pdf Japanese Knotweed Best Management Practices] which recommends smothering it:		The NH Dept. of Agriculture has a [https://www.agriculture.nh.gov/publications-forms/documents/japanese-knotweed-bmps.pdf Japanese Knotweed Best Management Practices] which recommends smothering it:

Watlington at 16:02, 16 January 2024

2024-01-16T16:02:52Z

← Older revision		Revision as of 16:02, 16 January 2024
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	'''''Fallopia japonica''''', a.k.a '''''Reynoutria japonica''''' and '''''Polygonum cuspidatum''''' ([https://gobotany.nativeplanttrust.org/species/fallopia/japonica/ GoBotany], [[wikipedia:Reynoutria_japonica\|Wikipedia]], [https://plants.usda.gov/home/plantProfile?symbol=FAJA2 USDA] -- [https://www.invasivespeciesinfo.gov/terrestrial/plants/japanese-knotweed NISIC]) is a very invasive species, which is very difficult to remove due to its large, deep, underground network of rhizomes. It is a perennial which can regrow to 10 ft. in height each year. It has a thick, hollow stem, and a distinctive heart shaped leaf.		'''''Fallopia japonica''''', a.k.a '''''Reynoutria japonica''''' and '''''Polygonum cuspidatum''''' ([https://gobotany.nativeplanttrust.org/species/fallopia/japonica/ GoBotany], [[wikipedia:Reynoutria_japonica\|Wikipedia]], [https://plants.usda.gov/home/plantProfile?symbol=FAJA2 USDA] -- [https://www.invasivespeciesinfo.gov/terrestrial/plants/japanese-knotweed NISIC]) is a very invasive species, which is very difficult to remove due to its large, deep, underground network of rhizomes. It is a perennial which can regrow to 10 ft. in height each year. It has a thick, hollow stem, and a distinctive heart shaped leaf.

	=== Removal ===		== Removal ==
	Removal is EXTREMELY difficult. The roots go very deep (up to ten feet), and spread horizontally. Any small piece of rhizome will sprout and regrow.		Removal is EXTREMELY difficult. The roots go very deep (up to ten feet), and spread horizontally. Any small piece of rhizome will sprout and regrow.

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	[[File:GreatHillLittlePlayingFieldJapaneseKnotweedRemoval.jpeg.jpg\|left\|thumb\|200x200px\|Smothering Knotweed at Great Hill]]		[[File:GreatHillLittlePlayingFieldJapaneseKnotweedRemoval.jpeg.jpg\|left\|thumb\|200x200px\|Smothering Knotweed at Great Hill]]
	An example of this smothering technique is along ~~one~~ side of the Little Playing Field at Great Hill. Most of it was done in 2022, with a final portion being covered in 2023 (report).		An example of this smothering technique is along the north side of the Little Playing Field at Great Hill. Most of it was done in 2022, with a final portion being covered in 2023 (report).

	=== Mis-Identifications ===		== Common Mis-Identifications ==
	'''Eastern Redbud''' (''[https://gobotany.nativeplanttrust.org/species/cercis/canadensis/ Cercis Canadensis]'', [[wikipedia:Cercis_canadensis\|Wikipedia]], [https://plants.usda.gov/home/plantProfile?symbol=CECA4 USDA] - [https://plants.usda.gov/DocumentLibrary/plantguide/pdf/cs_ceca4.pdf Factsheet]) Redbud saplings have a similar leaf, and can even have a similar shape. Redbud is a woody plant, however, unlike the hollow stem of Japanese Knotweed. And Japanese Knotweed is rarely found growing as a single stalk.		'''Eastern Redbud''' (''[https://gobotany.nativeplanttrust.org/species/cercis/canadensis/ Cercis Canadensis]'', [[wikipedia:Cercis_canadensis\|Wikipedia]], [https://plants.usda.gov/home/plantProfile?symbol=CECA4 USDA] - [https://plants.usda.gov/DocumentLibrary/plantguide/pdf/cs_ceca4.pdf Factsheet]) Redbud saplings have a similar leaf, and can even have a similar shape. Redbud is a woody plant, however, unlike the hollow stem of Japanese Knotweed. And Japanese Knotweed is rarely found growing as a single stalk.

Watlington: Created page with "400x400px '''''Fallopia japonica''''', a.k.a '''''Reynoutria japonica''''' and '''''Polygonum cuspidatum''''' ([https://gobotany.nativeplanttrust.org/species/fallopia/japonica/ GoBotany], Wikipedia, [https://plants.usda.gov/home/plantProfile?symbol=FAJA2 USDA] -- [https://www.invasivespeciesinfo.gov/terrestrial/plants/japan..."

2024-01-16T01:56:30Z

Created page with "alt=Picture of Japanese Knotweed plants, with flowers|right|frameless|400x400px '''''Fallopia japonica''''', a.k.a '''''Reynoutria japonica''''' and '''''Polygonum cuspidatum''''' ([https://gobotany.nativeplanttrust.org/species/fallopia/japonica/ GoBotany], Wikipedia, [https://plants.usda.gov/home/plantProfile?symbol=FAJA2 USDA] -- [https://www.invasivespeciesinfo.gov/terrestrial/plants/japan..."

New page

[[File:Reynoutria japonica in Brastad 1.jpg|alt=Picture of Japanese Knotweed plants, with flowers|right|frameless|400x400px]]
'''''Fallopia japonica''''', a.k.a '''''Reynoutria japonica''''' and '''''Polygonum cuspidatum''''' ([https://gobotany.nativeplanttrust.org/species/fallopia/japonica/ GoBotany], [[wikipedia:Reynoutria_japonica|Wikipedia]], [https://plants.usda.gov/home/plantProfile?symbol=FAJA2 USDA] -- [https://www.invasivespeciesinfo.gov/terrestrial/plants/japanese-knotweed NISIC]) is a very invasive species, which is very difficult to remove due to its large, deep, underground network of rhizomes. It is a perennial which can regrow to 10 ft. in height each year. It has a thick, hollow stem, and a distinctive heart shaped leaf.

=== Removal ===
Removal is EXTREMELY difficult. The roots go very deep (up to ten feet), and spread horizontally. Any small piece of rhizome will sprout and regrow.

Regular cutting/mowing can slow down its growth, but will not kill it and is not recommended as it will encourage the plant to spread horizontally. Care should be taken that the mower doesn't spread the material.

The NH Dept. of Agriculture has a [https://www.agriculture.nh.gov/publications-forms/documents/japanese-knotweed-bmps.pdf Japanese Knotweed Best Management Practices] which recommends smothering it:

* Allow it to start growing, then cut it flush to the ground at the beginning of June.
* Allow the cut material to dry out.
* Cover the area (including the cut material) with 4 to 6" of wood chips. The area should extend to at least two feet outside of any knotweed plants.
* Cover these wood chips with thick black plastic. 7 mil thickness is recommended, but hardware stores only stock 6 mil thickness as their "heavy duty" black plastic. A two foot overlap between sheets is recommended.
* Cover the black plastic with 4" of wood chips, to protect it. Be very careful not to puncture the plastic.
* If you do puncture the plastic, knotweed will find it and grow out. Remove the wood chips from that area. Remove any plant material and dry the plastic. Patch the hole, using more black plastic duct-taped down. Note that just patching a puncture with duct tape usually doesn't work, as the knotweed will push the duct tape off of the plastic. You need a bigger surface (the patch) weighed down with wood chips to contain it.

[[File:GreatHillLittlePlayingFieldJapaneseKnotweedRemoval.jpeg.jpg|left|thumb|200x200px|Smothering Knotweed at Great Hill]]
An example of this smothering technique is along one side of the Little Playing Field at Great Hill. Most of it was done in 2022, with a final portion being covered in 2023 (report).

=== Mis-Identifications ===
'''Eastern Redbud''' (''[https://gobotany.nativeplanttrust.org/species/cercis/canadensis/ Cercis Canadensis]'', [[wikipedia:Cercis_canadensis|Wikipedia]], [https://plants.usda.gov/home/plantProfile?symbol=CECA4 USDA] - [https://plants.usda.gov/DocumentLibrary/plantguide/pdf/cs_ceca4.pdf Factsheet]) Redbud saplings have a similar leaf, and can even have a similar shape. Redbud is a woody plant, however, unlike the hollow stem of Japanese Knotweed. And Japanese Knotweed is rarely found growing as a single stalk.