Water, Water, Water!
Newly planted trees have not established the extensive root system needed to absorb enough water during our hot, dry, windy summers. Even trees two or three years old should receive special care.
The secret is getting that water to soak deeply into the soil, so it evaporates more slowly and is available longer to the tree's roots. Because of the large surface area of soil that needs water, soaker hoses may not work and regular sprinklers may create run-off. By building a berm with at least a 4 ft. diameter around the base of the tree, and maintaining this “bowl” thru the first year, allows the water to percolate down through the soil, instead of spreading out. Mulch will also help to maintain soil moisture and temperature.
Most of the fine feeder roots that are responsible for the uptake of water are located in the top 12 to 18 inches of soil. It’s that area that should be kept evenly moist, letting only the top three to four inches dry out before re-watering. If the soil in that top 12 to 18 inches becomes too dry, the small feeder roots will die, impairing the tree’s ability to absorb water when it becomes available again. Be sure to check the soil moisture to determine when water is needed. You do this with a trowel, shovel, or soil-sampling tool. Don’t rely on the appearance of the soil surface, dig down and feel the soil several inches below the surface.
Mulch – see planting illustration above. Key is to not pile the mulch against the trunk of the tree, leave several inches of space between.
Also, keep the depth of the mulch at 3 inches or below, this will keep the moisture and temperatures level while not encouraging the roots to grow up into the mulch.
For the most part trees don't need additional fertilizers, the exceptions being fruiting or flowering trees. Example: magnolia's in clay soils sometimes need additional magnesium.
So, IF you CAN'T USE the correct fertilizer,
YOU ARE BETTER OFF NOT USING FERTILIZER AT ALL!!!!!!
Most limiting factor for trees IS NOT nutrients,