They are not tolerant of shade but are tolerant of juglone.

i have a couple old ones that have ended up in shade ... they dont die.. they just arent as prolific as when in sun ...

ken

Thank you both - I will try it - in a sunny spot!

I echo what Ken said. I grew up in a house that my family owned for my entire life, with lilacs under large black walnuts, and they did fine when the walnuts were a bit smaller, but when the shadows got larger, the lilacs started to look sad and get leggy.

We owned the house for 45 years and the lilacs were great for the first 25 years. After that, the walnuts were too big for the lilacs to do well.