We have a black walnut tree in the back yard. We planted arborvitae trees.........all of them died except the one further away.
What tall grasses or hedges would grow around the tree? We keep walnuts cleaned up (for the mower's sake).

to ATP, Trisha.

Walnut trees produce a compound called Juglone. It is a survival mechanism to help ensure the viability of the tree. Here is some info for you, including some lists of plants that can tolerate the juglone. The first is from OSU extension service. I hope this is of use to you.

http://ohioline.osu.edu/hyg-fa...

http://extension.psu.edu/plant...

There was an article posted here that might be of some help:
http://garden.org/ideas/view/f...

Yep Black walnuts they are great to look at but not really in the landscape IMHO, too many seedlings, the posion issue the sizes they can attain..

Do read up on them and hopefully you'll find a workable solution.