Tree Fertilizing

Karen Cambre, Sharpe, Kenneth W.  |  5/9/2018 4:05:53 PM

News article for February 5, 2018

Well Punxsutawney Phil, the winter forecasting groundhog, saw his shadow and has predicted 6 more weeks of winter. I was not surprised by his prediction, but not sure you can really take a groundhog seriously.

There are still winter chores to complete and now you have more time (maybe). There are a couple of plants besides citrus that seem to have taken a punch from our recent mid-teen weather. Agapanthus is one. You know it as Lily of the Nile or African lily. It is a native of South Africa and widely planted in the lower south. The plants I have seen have melted from freeze damage and the leaves have turned mushy. I think they will come back; usually they will survive down to between 10 and 15 degrees. I would go ahead and remove the damaged foliage to allow new growth a pathway toward sunlight.

damaged sago palmsjpg

I have also had a number of inquiries about Sago palms. Almost all of the ones I have seen, including my own, have damaged leaves that have turned tan. I would cut those damaged leaves off in early spring and you should get new growth from the center of the plant after the weather warms up.

February is the time of year to fertilize trees. It is especially helpful for young shade trees. The quicker you can get them up to size to provide shade, the better. Mature trees do not require annual fertilizing, but we recommend that you fertilize them every 3 years for maintenance purposes.

I have heard lots of ways to fertilize trees, but by far the simplest method is to broadcast fertilizer under the canopy of the tree while the grass is dormant. If you can time this application just before a slow rain or water it in, you will not have fertilizer run off and the dormant grasses will not pick up the fertilizer.

The rate of fertilizer can be calculated several ways, but I like to use the rate of 2 pounds of 8-8-8 fertilizer per inch diameter of the tree, measured at 4 feet of height. You then broadcast that amount of fertilizer under the tree canopy. The tree canopy is the sprawl of the limbs. So, if you measure a tree and it has a 14 inch trunk at 4 feet of height, that tree would require 28 pounds of 8-8-8 fertilizer spread out evenly under the tree. I would go out about 5 to 10 feet further out than the limbs and start my application about 2 feet from the trunk of the tree.

Some people want to dig holes and apply fertilizer in the holes, but I would recommend you not do that. Digging cuts roots and damages the tree. If you want to put the fertilizer in the ground, then use a rod (bean pole sticker) no larger than 1¼ inch in diameter to punch holes 8 inches deep. Another method is to use a 1¼ inch auger or long drill bit. These small holes will not damage the roots of a posthole digger or shovel. Make holes about every 15-18 inches apart and punch as many holes as needed for the volume of fertilizer to be applied. Again, make your holes symmetrical under the tree canopy to get even fertilizer distribution. I would use a hole pattern like spokes in a bicycle wheel. Place the first 4 spokes so you quarter the area under the tree, and then add your eighths, sixteenths, etc. until you get enough holes to accommodate all of your fertilizer.

The cooler weather of winter makes all this work easier and the wetter weather makes the ground softer if you want to make that many holes.

For more information on these or related topics contact Kenny at 225-686-3020 or visit our website at www.lsuagcenter.com.

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