En EspaŅol

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?


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
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
Not Yet Rated

Friday - May 28, 2010

From: Wichita, KS
Region: Midwest
Topic: Grasses or Grass-like
Title: Advice on grasses under walnut trees
Answered by: Nan Hampton


Little advice on grasses: I am prepared to plant zoysia under two walnut trees. Forgot about juglone-is this a good idea?


All members of the Family Juglandaceae (Walnut Family), including pecan, butternut and hickory trees as well walnuts, produce and release a chemical called juglone to defend their growing space against encroachment by other plants.  The amount or strength of the juglone released varies among the different species of the family.  I don't know which walnut trees you have, Juglans nigra (black walnut tree) or Juglans microcarpa (little walnut), but black walnut is reported to have the most, or at least, the most effective juglone. With this defense mechanism, called allelopathy, the tree adversely affects many other (but not all) plants. Juglone can be found in all parts of the black walnut tree. If the roots of another plant come within 1/2 inch of the walnuts roots, they can absorb the juglone and sicken and die. Also, walnut leaf litter and walnut fruit on the ground leach juglone into the soil. Virginia Extension Service has an excellent discussion of the black walnut and its allelopathic effects. Additionally, the article lists common plants that are affected by the juglone of the walnut. There is also a list of plants that will grow near the black walnut. There are other lists of plants affected by and/or tolerant of juglone (e.g., Cornell Cooperative Extension and University of Wisconsin Extension) but all of them are rather short on any grasses on the list.

A search for "zoysia" and "walnut or juglone" gave contradictory results with some evidence that juglone affected the grass and other evidence suggesting it was as much the shade as the juglone that was the culprit.  This is sort of all beside the point, however, because Mr. Smarty Plants wouldn't recommend zoysia in the first place since it is native to Asia and Australasia and what we are all about here at the Wildflower Center is "to increase the sustainable use and conservation of native wildflowers, plants and landscapes" 

I can, however, offer some substitutes.  There are no native turf grasses that do well in the shade, but there are a few possibilities for ground covers that are shade-loving and juglone resistant.  Here are a few:

Chasmanthium latifolium (Inland sea oats) is an attractive clumping grass that loves the shade and isn't affected by juglone.  (This is a personal observation since I have a large population of inland sea oats growing under my black walnut tree and it has grown there for several years).  Here is more information.

Sedges are resistant to the effects of juglone and they grow well in the shade.  Carex blanda (eastern woodland sedge) is native to Kansas and would make a good ground cover.  Here is more information and photos of Carex blanda.

Ferns are also resistant to juglone and grow well in the shade.  Here are some suggestions native to Kansas:

Asplenium platyneuron (ebony spleenwort) and here is more information.

Onoclea sensibilis (sensitive fern) and here is more information.

Chasmanthium latifolium

Carex blanda

Asplenium platyneuron

Onoclea sensibilis





More Grasses or Grass-like Questions

Habiturf lawn for townhouse in Austin
October 06, 2013 - Hi Mr. Smarty Plants, I live in central Austin and on November 1st I will be moving into a townhome with a small yard of around 500 square feet. The yard has been neglected and currently looks to ...
view the full question and answer

Dead, brown Habiturf lawn
July 07, 2015 - I planted Habiturf seeds last fall and had a good lawn all winter. Now the grass is brown and dead. Did it drown with all the rain we have had? If so, what should I do now? If not, what should I do...
view the full question and answer

Low Groundcovers for Pennsylvania
September 18, 2015 - Hi Mr Smarty Plants, I'm looking for a low growing grass or ground cover for an area that is between my neighbors horse fence and mine it is about 2 feet wide 30 ft long. It is impossible to mow and ...
view the full question and answer

Ground cover for steep slope in Washington DC
May 07, 2010 - We have a steep slope in our garden in Washington DC which has sun from noon to sun set. Could you please recommend some low maintenance plants which would be a good ground cover and limit erosion?
view the full question and answer

Do I need to cover my Habiturf planting with straw?
March 02, 2012 - I'm preparing to seed the Habiturf in my front yard in a couple of weeks. My dad has suggested I spread some straw to help protect the seeds. Your thoughts? Thanks!!!
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.
© 2015 Lady Bird Johnson Wildflower Center