You should fertilize your trees based on what you are trying to accomplish. When growing my trees to get them as large as i can as fast as i can i use chemicals with a higher nitrogen amount during the growing season, but go down on nitrogen when it gets really hot, and then before winter. If i am just maintaining the trees, i use a balanced fertilizer that is slow release, like cakes. As far as brands, it doesnt really matter, just look at the numbers, and mix according to the directions. Good luck.