Question
Hi,
We removed a black walnut tree 8 years ago.  I was wondering if the toxins would be out of the soil by now, as I am interested in extending the garden over to that area next year.

Answer
Hi Renee, Juglone is known to be released for several years as the roots begin to decay. It does not move through the soil well so it is possible that juglone sensitive plants could still be affected.  I've never seen any research on exactly how long it persists.  
I would suggest that you test a few inexpensive juglone sensitive plants like tomatoes or peppers and see what happens.  
There are many juglone tolerant plants that you may want to use.  Check with you local nurseryman for those that would be hardy where you live.  You can find many lists on the Internet.  Jim