Certified GKH Gardening Expert
You don't say what type of tree you have; different trees require different feeding. If it's a fruit tree, here is information about using food spikes. If it is not a fruit tree, search our database for the type of tree at https://www.gardeningknowhow.com. You can also ask your local extension agent who will be well versed on the trees in your area and how to best fertilize them.