We're in western Washington state on a silty loam bottom soil, zone 8B.
Across the fence about 20 feet is a 70 foot tall black walnut tree.
We grow rhododendron and azalea.

So far, we have not noticed symptoms of juglone toxicity in the rhodies, but then, I don't know what to watch for. And if/when symptoms show up, what can be done?

Any hints?

The biggest problem is decomposing leaves leaching juglone into the soil but once there, it could take years to dissipate. Are your plants outside the leaf fall zone?

Symptoms are wilting, yellowing plants. The juglone disrupts part of the chemistry of photosynthesis.