Fertilizing trees

What tips can y'all give for fertilizing sawtooth oaks that are about 15 years old? The main thing I need to do is clear out some junk that has grown up around them and I'll start working on that this weekend. When to fertilize? Would it help to try to get the fertilizer down into the soil below the grass/weed roots?

Also, there are a couple bags of 8-8-8 that have been sitting in the barn for years. Do you think it's still good for anything?

Dig some post holes a few feet deep during the growing seasons, March-September, put some fertilizer in, and cover back up.

I had an arborist come to my house a few months ago to look at a maple tree I want to nurse back to health. He said the "tree and shrub" fertilizer available at Lowes was about the best stuff you could use. He said buy it and follow the directions on the label.

Outstanding results using fertilizer stakes. Using fertilizer stakes allows tree to receive a slow release of food over a longer period of time. Makes a huge difference. Use a one inch lead pipe and a large hammer, drop fertilizer stake in hole and cover up. I do this two or three times a years. Site One sells boxes of 300 for about $80.00, use to be called John Deer Landscaoping and Lesco before that. Small trees less than inch in caliper use four stakes 18 inches from trunk, some of my larger trees I use 10 stakes at drip edge.

Be really careful - we killed to great producing persimmon trees several years ago by apparently applying too much fertilizer by this method.

I have several people tell me that you give your trees "candy" on the candy days...Valentines and Halloween.

Too much nitrogen causes fruit drop in persimmons.