Prevent Tree Fertilization Problems:
Stick with the higher ratio nitrogen fertilizers unless your tree is determined to be deficient in potassium or phosphorus (take a soil test). An N-P-K (nitrogen, potassium and phosphorus) ratio of 10-6-4 is a great choice and would be even better in a "slow release" formulation. Stay at less than .20 pounds of nitrogen per 100 square feet of root zone application area depending on tree species and size.
How You Can Over Fertilize a Tree:
You can actually kill a tree if you apply too much fertilizer. The most common ways to over-fertilize a tree is using an equal ratio of all three essential nutrients (nitrogen, potassium and phosphorus), applying more material than the standard recommended application rate suggests and using fertilizers that are designed to be "fast release". Combining any or all of these conditions will increase the chance of tree root damage. Too much fertilizer introduces toxic "salt" levels to the root system.
Treating an Over Fertilized Tree:
OK. So you realize you have over fertilized your tree. The tree may survive if you do a fairly simple, three part treatment as quickly as possible: (1) remove the dying or wilting leaves if you have any. (2) Water the fertilized portion of the soil to a "flushing" point - that means you need a source for a lot of water and (3) cover the critical root zone with a carbon based mulch - preferably composted leaves and
grass - and flush again.
