Schedule for Fertilizing Oak Trees in Florida

First Season

• Fertilize a newly planted oak four to six weeks after planting. If you've planted in early spring, a second application in October is recommended. For fall plantings, fertilize four to six weeks after setting the tree in the ground, and wait until the second year to begin feeding the tree again. In addition, it's important to keep your lawn's fertilizer schedule in mind if the oak is growing near maintained turf. Wait at least two weeks after fertilizing your lawn to apply fertilizer to the oak.

Years 2 to 5

• The University of Florida's Institute of Food and Agricultural Sciences recommends that young oak trees, along with other shade trees, be fertilized in early spring and in the fall. In Florida, this recommendation translates to a February and an October application of fertilizer. IFAS notes that in some cases a midsummer feeding may be called for. Specifically, a rainy summer season -- typical for Florida -- may leach nutrients from the soil. During wet summers, give oak trees a supplemental feeding in July or August. As with the oak's first season, don't apply fertilizer within two weeks of a lawn feeding.

Subsequent Years

• After your oak tree lives past its fifth summer, it is unlikely to need fertilizer. Older oaks develop root systems that enable them to tap into nutrients well beyond their above-ground locations. If your tree isn't situated near a maintained lawn or garden, however, it may begin to show signs of nutrient depletion. These symptoms include yellowing leaves, mottled leaves and stunted growth. In addition, nearby construction can damage the roots of older trees, in which case the phosphorus in standard fertilizers is especially welcome to rejuvenate the tree's underground parts.

Basic Fertilizer

• Nitrogen is the most important element in a fertilizer for an oak tree. In an NPK (nitrogen, phosphorus and potassium) fertilizer blend, you'll want one in which the ratio is 3-1-2 or 3-1-3, as with 15-5-15. For optimal oak tree growth at the sapling and young tree stages, use 2 to 4 pounds of "actual nitrogen" per 1,000 square feet. For a sapling, this generally translates into 2 pounds of 15-5-15 for a 10-by-10 area, which provides 0.3 pounds actual nitrogen. As the tree's root system spreads, you'll be using a larger amount of the NPK blend. To calculate the square footage you need to fertilize, multiply the area under the tree's branches by about 1.5, because roots extend beyond the tree's drip line. Slow-release formulations are best for oak trees.