I have a few really old oaks and hickories that seemed like they were getting tired. Out by the road, the Road Commission has been putting salt down and that's not helped, either. I bought some tree fertilizer stakes from a lawn & garden place and pounded them into the root areas as per the instructions. (I seem to remember a few per tree at a distance 10 - 15 ft from the trunk.
Well now the trees look terrific. They even have started new growth from some of the lower limbs that I was about to trim off. I saw a huge increase in nut production, too, which the squirrels have taken note of.
Not sure if this is relevant, but at the same time I got a few honeybee hives. That has resulted in an increase in wildflower populations, but all the trees seem to be in better shape, including maples, pines, ash and some new birches. The bees cover a huge amount of territory, even the neighbors have noticed the increased bee presence.
Anyways, the fertilizer stakes plus the bees seem to have produced a "feel good" appearence as far as the large trees are concerned. You can see it in the Spring when viewing them and bushes using 'blue blocker' sunglasses. The healthy growth is a rich green while the ill trees are a lighter color. Mine now look great. Down the road, they look like they are slowly dying.
