Replacing A Black Walnut-FAQ

Replacing Black Walnut

Question:
In a storm last year, we lost a black walnut tree that shaded the house and shade garden plantings. This spring we removed the tree and roots from an area 4' wide and 4' deep. We're considering replacing this tree with a thornless honeylocust or hackberry. We want a tree that will tolerate any remaining black walnut juglone, has deep roots so that I can place shade plants close to the tree and will provide a moderate amount of shade. (The other trees in the area are a maple and ash.) Which tree would you recommend? Minnesota Master Gardeners say:
A good website for black walnut toxicity is:http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h407blkwal-tox.html

The black walnut juglone is most concentrated in the roots, and the feeder roots are very tiny, so the chances are you still have a lot of black walnut roots left. Hackberry is one of the trees susceptible to black walnut toxicity, so I would not recommend planting one. However, honey locust is one of the trees tolerant of black walnut toxicity. See the Extension Service website on trees and shrubs for a short description of the honey locust. This site has information on seeds, leaves, possible diseases, varieties, etc. Note that the Twin Cities are at the northern edge of where you can grow this tree. http://www.extension.umn.edu/distribution/horticulture/components/DG0545tree.html

There has not been much research on what does and does not grow under a black walnut. Many of the lists one finds are based on observation. So you may end up trying something and failing.

Here are two more websites with lists of possible plants for growing near a black walnut. From the Ohio State University: http://www.ag.ohio-state.edu/~ohioline/hyg-fact/1000/1148.html

From the Virginia Cooperative Extension:
http://www.ext.vt.edu/pubs/nursery/430-021/430-021.html
Please use these two websites with caution. Some of the plants in their lists are not hardy in Minnesota.
I might also suggest you get a soil test done before planting. Go to http://soiltest.coafes.umn.edu/Lawn/garden.htm