En Español

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

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

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

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 fern
Adiantum pedatum

Common lady fern
Athyrium filix-femina

Bunchberry dogwood
Cornus canadensis

Crested woodfern
Dryopteris cristata

Virginia waterleaf
Hydrophyllum virginianum

Christmas fern
Polystichum acrostichoides

Inland sea oats
Chasmanthium latifolium

Plantainleaf sedge
Carex plantaginea

Fan clubmoss
Lycopodium digitatum

More Shade Tolerant Questions

Plants for a condo garden in Decatur GA
February 12, 2009 - I recently moved into a condo in Decatur (just outside Atlanta). I am now working on the back yard - just a patio and dirt right now. It is a small space and is shaded much of the day but does get s...
view the full question and answer

Native shade plants for sandy soil in New York
April 30, 2008 - I have a small patch (about 10 feet x 6 feet) of shady ground next to my house. The soil is very sandy. I really would like some perennial color - or at this point, anything actually - that will grow...
view the full question and answer

Erosion Control with perennials for a shady Dallas bank
July 25, 2013 - Thank you for your help with turf or perennials on a shaded bank, 4000 sq ft, for the Dallas area that has good roots, grows in semi shade to shade, is on a steep bank so cannot mow, and flowers the l...
view the full question and answer

Native Shade Tree for Central Texas
February 26, 2011 - My parents are buried in Round Mountain Cemetery close to Marble Falls, TX. Can you recommend a tree or shrub we can plant to shade their graves? We need something that can survive and grow in the h...
view the full question and answer

Plants for under Oak Trees in LA.
March 05, 2013 - What type of plants and grass can be planted under and around oak trees
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | JOBS | SITEMAP | STAFF INTRANET
© 2016 Lady Bird Johnson Wildflower Center