I have 2 Black Walnut trees 3 years old and 6 feet high. Both are in sunlight most of the day. One is lush dark green and the other is vary light green almost yellow. What is causing this?

Hi and welcome Pictures would help us a lot to help you out here. If you can show both trees in one picture, plus a closer picture of the light green one that would be great.

It's most likely to be a difference in the soil pH causing the yellowish tree to become nutrient deficient. Is it closer to a concrete structure of some type, like a driveway or a sidewalk? The leachings from concrete can drastically affect the soil pH. That's the best I can think of off the top of my head. Please post some pictures!

This has affected me both personally AND professionally. I'll spare you the story and suggest you look up " Thousand Canker Disease ",a few years ago, I represented our local District in an emergency meet with the Co. Forestry Service. Pretty sad with what's happening. Hope this isn't it, but be vigilant.

Good Luck