Yesterday ZilyZily told me that the volunteer tree growing in my neighbor's backyard (fairly close to our property line) is a Black Walnut tree. It's grown to about 9 - 10 feet tall fairly quickly - just from a nut some squirrel buried. On the other side of our joint fence (my side) is a 25- year old orange tree which is about the same height as the Black Walnut tree. They are growing fairly close together - separated only by our joint back fence. Lately the orange tree leaves are turning yellow in spite of regular/normal watering by me. My neighbor is even alarmed because we share the oranges and she doesn't want my orange tree to die. I read on Wikipedia that Black Walnut tree roots emit some kind of toxic chemcal which gives them an advantage over other plants. Could this be killing my orange tree? If so, my neighbor has offered to cut down the Black Walnut and plant another kind of tree there on her side. I just want to know if these two trees can co-exist well into maturity. I know that the Black Walnut can get 130 feet high - especially those growing from seed. And eventually the shade from the large canopy may kill the orange tree if the toxic root chemical doesn't. Please let us know if these two trees can co-exist. I'm going to fertilize the orange tree to make sure that's not the problem. I've watched the orange tree growing for many years now and I've never seen the leaves look this yellow. Attached is a picture of my orange tree taken on 2/14/21 before the leaves started turning yellow. The Black Walnut tree is just to the left in the picture (no leaves since it's deciduous). It's grown even taller in the last 3 months. Maybe the root chemical is not active during its dormant winter period? The last picture shows the Walnut tree as it looks now (with leaves). Thanks in advance.
