Black Walnut and Japanese Maples
This maybe helpful to a few gardeners out there. I have a large 50 foot Black Walnut tree that came with my property when I bought it, and of course didn't know about Juglone (poisonous to many trees/shrubs) that comes off of its roots and fruits, etc.. Anyhow, this year my Scotch Pine is almost dead. I planted it last year, and everything seemed fine. I watered it adequately. Its roots were fine, etc.. Now inexplicably it is beyond life support.
Now its not conclusive but I believe that the Walnut is within range of the Juglone to work its poison (within 40 feet). It may be the culprit for its demise.
On the other hand I have an AP 'Hogyoku', and an AJ 'Aconitifolium' right under the canopy of this old beast. It rained down those messy fruits in the fall, etc., and has not had any effect on them (of course I removed the fruits whenever they fell nearby). Thankfully, despite my ignorance, I found out that Acer Palmatums are immune to Juglone.
What is odd is that the Scotch is in the backyard seemingly far from its canopy but it seems extra sensitive, and the APs are under the canopy and they are fine.