En EspaŅol
Share

Ask Mr. Smarty Plants

Mr. Smarty Plants - Plants to replace <i>Polygonum cuspidatum</i> ( Japanese knotweed)

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.

Need help with plant identification, visit the plant identification page.
 
rate this answer
1 rating

Saturday - August 10, 2013

From: Chippewa Falls, WI
Region: Midwest
Topic: Invasive Plants, Shade Tolerant
Title: Plants to replace Polygonum cuspidatum ( Japanese knotweed)
Answered by: Nan Hampton

QUESTION:

I live in a heavily wooed area of Chippewa Falls, WI. Our property is covered with Giant Japanese Knot Weed. We have been trying to get rid of it for years. We are finally going to try using the dreaded, Round UP, after trying many natural techniques and solutions over the years to no avail. Even covering them up with dark AND clear plastic sheets hasn't worked. We are wondering what sort of fast growing/spreading ground cover we could plant to try to crowd out what may survive of the knot weed once we use the chemicals. What might we seed the area with that would be native to our area? We have deep shaded wooded areas, with a few depressions of standing water with hard rains. Also have shady and sunny areas up next to the house where the knot weed is prolific. Thank you for any suggestions.

ANSWER:

Polygonum cuspidatum [synonym=Fallopia japonica] (Japanese knotweed) appears on the Plant Conservation Alliance's (PCA) Alien Plant Working Group's LEAST WANTED list.  Please read their "Management Options" sections for control methods.  The USDA Plants Database has a distribution map for North America plus a list of states (under "Legal Status") where it is considered prohibited, banned, invasive or noxious.  We do understand you have a serious problem here.  There is an Invasive Plants Association of Wisconsin that has a website with a great deal of useful information, including a list of Regional and County Groups that deal with invasives in Wisconsin.

Now, with that said, finding species that will "outcompete" this very tough plant (according to the PCA's LEAST WANTED web page "can tolerate a variety of adverse conditions including full shade, high temperatures, high salinity, and drought") is not going to be an easy task.   We can recommend species that will do well in the conditions you give for your site, but you are going to have to continue to be vigilant and deligent in removing/destroying the knotweed as it reappears.  Sorry to deliver that bad news—but you probably already realized that was going to be the case.

Let's start with suggestions for the deep-shaded wooded areas with moist soil:

Arctostaphylos uva-ursi (Kinnikinnick) is a trailing evergreen shrub that makes a good groundcover in shady areas.  It will also grow in sun and part shade.

Adiantum pedatum (Northern maidenhair) and Athyrium filix-femina (Common ladyfern) are deciduous ferns.

Cornus canadensis (Bunchberry dogwood) makes an excellent low groundcover in shady woods.

Dryopteris cristata (Crested woodfern) is a partially evergreen fern that grows in sun, part shade and shade.

Hydrophyllum virginianum (Eastern waterleaf) grows in part shade and shade in moist woods and is labeled as an "aggressive grower"—a good candidate for competing with the Japanese knotweed.  Here are more photos and information from Robert W. Freckman Herbarium University of Wisconsin.

Polystichum acrostichoides (Christmas fern) is an evergreen, clumping fern.

Chasmanthium latifolium (Inland sea oats) is one of the few grasses that grow well in shade.  It is said to be aggressive in spreading.  Here is more information from Missouri Botanical Garden.

Carex plantaginea (Plantainleaf sedge) is an evergreen grass-like plant.  Here is more information from Illinois Wildflowers.

Lycopodium digitatum (Fan clubmoss) is an evergreen, low growth plant with a spreading habit.  Here is more information from Illinois Wildflowers.

You can search for more possibilities by doing a COMBINATION SEARCH in our Native Plant Database.  Choose "Wisconsin" from Select State or Province, "Shade" from Light Requirement, "Moist" from Soil Moisture and both "0-1 ft" and "1-3 ft" from Size Characteristics.  You, of course, can change or add characteristics for your search.  For instance, choose "Sun" from Light Requirement for the areas near your house.

Prairie Nursery in Westfield WI has Native Ground Covers for sale as well as other native plants.  Prairie Moon Nursery in neighboring Minnesota has native seeds and seed mixes for sale (e.g., Shady Woodland Seed Mix for Wet Mesic to Dry Mesic Soils).  You can find more nurseries and seed companies that specialize in native plants in your area by search in our National Suppliers Directory.

 

From the Image Gallery


Kinnikinnick
Arctostaphylos uva-ursi

Northern maidenhair
Adiantum pedatum

Common ladyfern
Athyrium filix-femina

Bunchberry dogwood
Cornus canadensis

Crested woodfern
Dryopteris cristata

Eastern waterleaf
Hydrophyllum virginianum

Christmas fern
Polystichum acrostichoides

Inland sea oats
Chasmanthium latifolium

Plantainleaf sedge
Carex plantaginea

Fan clubmoss
Lycopodium digitatum

More Invasive Plants Questions

Invasive non-native mulberry and groundcover in Jacksonville FL
October 02, 2011 - Northeast Florida (Jacksonville) inland. My mulberry tree provides dense shade in the summer and filtered light the other seasons, leaving sand in its growing area. What fast growing ground cover woul...
view the full question and answer

Are These Plants Natives for Flower Mound, Texas?
September 24, 2010 - We are having our flower beds reworked and these are the plants that the company is recommending to plant. I would like to know if these plants are native to our area:pink muhly grass, lythrum, lorope...
view the full question and answer

Is it OK to plant Huisache in southern California?
June 15, 2009 - We have a wonderful huisache growing on a very dry rocky/dusty slope. It has now sprouted babies and we are delighted because we have room for several more on this slope. I have some room on our front...
view the full question and answer

Removal of poison ivy by goat in Lone Jack MO
May 29, 2009 - Easy organic removal of poison ivy?? I bought a goat, but you can borrow a neighbors. Always get 2 as they get lonely. They love to eat poison ivy, pull up vine roots and all, and leave the grass.
view the full question and answer

Non-branching mimosa tree
June 26, 2008 - I have a Mimosa Tree, just about 2 years old, grown from seed. The problem with it is that it has not branched out, it looks like one long branch growing out of the ground, about 5 feet if stood strai...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center