Experts and BHG readers answer.
fading leaf color on Beechnut tree
"Some cultivars of European beech (Fagus sylvatica) have a lighter, almost chartreuse colored leaf, so make sure that's not the cause. You should also do a pH test of your soil (you can get an inexpensive pH kit at the garden center) to make sure the soil is slightly acid (between 6 and 6.5), which is what beech trees prefer. You can change the pH and make it more acidic with coffee grounds, pine straw, sawdust (be sure to add nitrogen fertilizer at the same time to account for what will be drawn from the soil to breakdown the sawdust), sulfer, or iron chelate.
Luke Miller, editor
Garden Ideas & Outdoor Living magazine"