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Noah Jansen

Variegated Japanese knotweed

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I recently saw a variegated cultivar of Japanese knotweed for sale.  The seller claims it is a is a clump former, not a runner and is not invasive.  It is also supposed to have only male flowers and thus, produces no seeds.  Does anyone have any experience with variegated knotweed?  Should we be concerned about it as an invasive species?

I also wanted to ask about the law in Michigan.  The way I read it, all Fallopia japonica is prohibited, including cultivars, but I just wanted to verify that this variegated form is illegal to sell.

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Prohibited Plant Species (Natural Resources and Environmental Protection Act (Act 451 of 1994, as amended):
Prohibited species identified under this Act cannot be sold or grown in the state. Any of the following plants, fragments, seeds or a hybrid or genetically engineered variant thereof are specifically prohibited.
(and then Japanese knotweed is listed)


From the DNR factsheet:
Japanese knotweed is legally prohibited in Michigan. It is illegal to possess or introduce this species without a permit from the Michigan Department of Agriculture, and Rural Development except to have it identified or in conjunction with control efforts.
 
 
I'd say there isn't a lot of room for interpretation, and the cultivar is illegal.  This is also important in no small part because the flowers still have the ability to cross with giant knotweed, creating the even-more-aggressive hybrid, Bohemian knotweed.

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I agree with Katie's interpretation, still illegal.  Although I would note that from experience cultivars may not be as aggressive (still not a reason to plant them).  WRISC dealt with a small dwarf knotweed population in 2014, Fallopia japonica var compacta.  Only knotweed population to kick the bucket with one herbicide treatment. 

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