Have you heard about “Japanese knotweed”? Regionally it is also known as “Michigan Bamboo” or even just “bamboo”. Several concerned residents have brought this fast growing plant to The City’s attention and we’ve put up this informational page to help spread awareness.
Left: Bamboo Right: Knotweed
What is Japanese knotweed?
Japanese Knotweed is an invasive species of concrete-busting plant that can cause damage to both city infrastructure and natural environments. It is very easy to spread and grows above and under ground at an exponential rate. Control is extremely difficult and expensive once the plant is established, so early detection and prevention of spread are the best weapons at this time. Cities all over the world, especially in the United Kingdom, are starting to become aware of this threat and take action. In 2005 the State of Michigan declared it “illegal to possess or cause to grow” (see below for more on legal designation)
- Bamboo-like stems can be up to 10ft high
- Look like red asparagus when starting out
- Grow 2-3 inches a day
- Shovel shaped leaves with flat top edge
- Older stands can be so thick they’re hard to see through
- Deeply-penetrating rhizomes (creeping underground stems) and “crowns” [Picture of crown]
- Underground, these can be up to 65ft in all directions, and up to 10 ft down
- Lacey white flowers in Aug-September- not to be confused with pokeweed
Left: Pokeweed Right: Knotweed
There are four main reasons why Japanese Knotweed is a problem in Kalamazoo and elsewhere:
- It can cause structural damage to buildings and paved structures
- It spreads easily via rhizomes and cut stems or crowns
- It out-competes native flora, harms biological diversity
- It is difficult and expensive to control or eradicate.
Examples of negative effects:
- Damage to roads, sidewalks, parking lots, and building foundations [picture of damage]
- Blocks access and obstructs visibility on roads, alleys, drives, and foot paths
- Damage to archaeological sites
- Dried cane debris pose fire and flooding hazards
- Damage to flood defenses
- Increases erosion when the bare ground is exposed in the winter.
- Compromises the stability of river banks
- Impacts breeding and feeding areas for fish and wildlife
- Restriction of access to riverbanks for anglers, bank inspection and amenity use.
- Displacing of native flora and fauna
- Shades out and poisons other plants
- Obstruction of light to windows and gardens
- Accumulation of litter in well established stands
- Expensive to treat (chemical treatment hand injected or sprayed multiple times a year, 5-8 years, and includes re-landscaping)
- Reduction in land property values in some areas
How it spreads
Pure Japanese Knotweed seeds are sterile. This plant is a female that makes copies of itself by “vegetative reproduction,” meaning pieces of plant or rhizome break off and begin to grow where they come to rest. This plant material can be transported to a new location by:
- water, if the parent plant is close to a river or stream
- moving soil which contains them
- dumping/leaving cut or pulled stems on the ground
- illegal dumping has caused many infestations around Kalamazoo
If Giant Knotweed is growing near Japanese Knotweed, they can hybridize creating Bohemian Knotweed [picture] which comes with all the same problems as its parents, but with the added problem of having fertile seed. Giant Knotweed should be dealt with first in these cases, if possible.
Japanese knotweed is an opportunistic plant that will grow almost anywhere a piece of stem or root falls on soil. It prefers the following places because of open access to sunlight and/or disturbed soil:
- waste ground
- along watercourses
- areas of previous dumping
Individual plants can cover several square yards of land, joined up below ground by an extensive rhizome network
What You Can Do
1. Your Property
If you have identified and positively confirmed Japanese Knotweed on your property, keep an eye on it. Do not ignore it. Don’t try to cut it down, dig it out, or poison it without consulting an expert. These actions stimulate growth, making the problem worse. If you must cut the canes for access, bag all material and dispose of in regular trash. DO NOT compost or send to Green Waste.
It is not illegal to have Japanese Knotweed on your land, and you do not need to notify anyone about Japanese Knotweed on your land. You are not obliged to remove or treat Japanese Knotweed, but you must not:
- allow Japanese Knotweed to spread onto adjacent land - the owner of that land could take legal action against you
- plant or encourage the spread of Japanese Knotweed outside of your property. This can include moving contaminated soil from one place to another or incorrectly handling and transporting contaminated material and plant cuttings
If you would like to submit pictures for review, or schedule a visit from our Tall Grass and Weeds Inspector to identify please email firstname.lastname@example.org
2. Other people’s property
If you think someone has Japanese Knotweed on their property, make friendly contact with them to see if they are aware of it. Direct them to this webpage and the resources listed. Please be understanding in that this plant is extremely hard to control and takes years of effort to achieve. A property owner may be taking steps to control it already without much visual success. Ultimately this is going to be a problem solved as a community, and may require several neighbors pooling resources and agreeing together to treat an infestation, as Japanese Knotweed doesn’t understand fencelines.
3. City Land
If you believe Japanese Knotweed is growing on City property, please report it http://www.kalamazoocity.org/report-a . We are working with experts from several state and local organizations to develop treatment plans for our properties. Treatments are site specific and shouldn’t be replicated without an expert opinion.
4. Other entities land (i.e. Rail, Consumer Energy)
If you believe that Japanese Knotweed is growing on land owned, managed and maintained by another entity (this includes railway tracks and property both used and disused) then you can it report directly to that specific property owner.
What The City of Kalamazoo is doing:
- Public education and outreach with the goal of reducing the spread of Japanese Knotweed and other invasive plants.
- Mapping locations of Japanese Knotweed on public property using the app for the Midwest Invasive Species Information Network (MISIN) at http://www.misin.msu.edu/report/. This information will be used to help experts determine the extent of the infestations and help with prioritizing treatment sites.
- Collaborating with other local and regional governments, as well as environmental organizations, to develop effective and coordinated control programs in our region. Control is difficult and slow as it can take several treatments and inspections over multiple years to ensure the roots are killed.
“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.” – Michigan Department of Natural Resources Japanese knotweed Best Control Practices Worksheet http://www.michigan.gov/documents/dnr/knotweed_BCP_372280_7.pdf
As further research is being done on Japanese Knotweed, positive uses are being discovered. Articles online are beginning to feature recipes with the encouragement, “Eat the Invaders”. You should be cautious about eating ANYTHING wild- make sure you know 100% what you are collecting.. DO NOT INTENTIONALLY PLANT THIS PLANT. It is a VERY bad idea- and ILLEGAL- to plant Japanese Knotweed somewhere it isn’t already growing Even when planted in a pot, escape has happened. Also, this plant can sense when it’s being fed upon, and cutting it stimulates growth, causing it to increase in size. “Eating the Invaders” in this case could make the problem worse.