Sharpe's Point

Kenny Sharpe

Trees are still on the list of tasks to accomplish during the winter months.

Trees are basically maintenance-free — except for raking leaves and picking up fallen limbs — but one helpful chore would be fertilizing those that need it.

Mature trees don’t need to be fertilized every year and are usually only fertilized every three years if you aren’t trying to increase size. Those trees that are still growing will benefit from an annual fertilizer application. Young trees that are properly fertilized can add as much as 20 percent to their growth in just one year.

February is the best time to fertilize healthy trees. If your trees are stressed, there is information that indicates you are better off waiting until after they put on their leaves before fertilizing them.

But first things first, what is a stressed tree?

Stressed trees would be those in a new subdivision development that are suffering from soil compaction and other construction damage; or trees that have been struck by lightning; or trees whose roots have been damaged by the new swimming pool, new driveway, or new house.

We do not want to over-fertilize stressed trees early because they already have limited root systems, and you don’t want to flush the excess foliage that the limited roots have to support.

For healthy trees, I like to place the fertilizer in holes under the canopy of the trees. This will allow trees to get the benefit of the fertilizer, which won’t get overtaken by the grasses and weeds or washed off with rains.

You can use a drill bit and auger or large drill to make holes about ¾-1¼ inch in diameter and about 8 inches deep. For this task, I personally like to use a bean pole sticker (If you are unfamiliar with that term, it is a heavy bar or pipe that is thrust into the ground to make a hole). Do not use a shovel or post hole digger — those holes are too big and will damage the tree’s root system.

Imagine you’re putting spokes in a bicycle wheel. Start your first hole 2-4 feet from the base of the tree and add a hole about every 18-24 inches until you get 10 feet past the drip line (branch ends). Once you get that spoke complete, go back and add as many spokes as necessary to symmetrically cover the area under the canopy with the amount of fertilizer needed. Then fill each hole with fertilizer.

There are two methods to calculate the amount of fertilizer needed per tree. One is mathematical in nature. You can put down 5 pounds of complete fertilizer such as 8-8-8 or 8-24-24 per 100 square feet of area under the canopy of the tree. This method of fertilization assumes that you do not have grass sod under the tree canopy, which is not what I usually see.

Now, if math is not your strong suit or if you have grass under your tree limbs, you can use the old method: Apply 2 pounds of 8-8-8 or 8-24-24 fertilizer per inch diameter of tree trunk, and measure the trunk at 4 feet above the soil line.

Winter is the best — and coolest — time to fertilize trees.

For more information on these or related topics, contact Kenny at (225) 686-3020 or visit our website,

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