Gardening

Gardeners' Q&As From The Galveston Home & Garden Show

by William M. Johnson
March 10, 2005

A "Tip of the Trowel" is extended to Master Gardeners who answered visitors' questions at the recent Galveston Home and Garden Show. Shown (left to right) are Joan Rossano, Shan Revak, Bob McPherson, Suzi Hayes, Patricia Smith, Wayne Elliott, and Nancy Lee Peterson. Not pictured are Herman Auer, Raford Brister, Ronnie DeVasier, Lynne Green, Carol Jean Hebert and Clarence Paul. Photo credit: Herman Auer

The 17th Galveston Home and Garden Show was recently held at the Galveston Island Convention Center. Thirteen Texas Master Gardeners with the Galveston County Extension Office had two informational booths. They distributed publications and plenty of visitors came by to ask plenty of gardening questions.

The Master Gardeners provide considerable assistance to the Galveston County Extension Office in providing educational programs on horticulture. The next time you meet a Master Gardener, please give them a thank you for their service to our community residents.

The following is a sampling of the questions we received.

Question: I recently moved here from the Midwest and have always heard that lightning helps provide nitrogen to the soil. Is there any truth to this?

Lightning is an intriguing occurrence-it frightens us on some occasions and it captivates us on other occasions. Over the continental 48 states, an average of 20,000,000 cloud-to-ground flashes has been detected every year since a lightning detection network was established in 1989 to monitor all of the continental US. In addition to cloud-to-ground type flashes, there are roughly 5-to-10 times as many cloud-to-cloud flashes.

Gardeners know that nitrogen is one of the most important things you can give your plants to keep them happy and healthy. There's actually lots of nitrogen in the air as our earth's atmosphere consists of slightly more than 75% nitrogen.

Unfortunately for the plants in your landscape, most of that nitrogen is not in a usable form. So how can it help your plants if the nitrogen is stuck in the atmosphere in an unusable form? This is where the lightning comes in. Most gardeners and folks in general are surprised to learn that some of the nitrogen in the soil comes to your plants courtesy of lightning.

When lightning bolts discharge, intense heat is produced and this process (known as ionization, for those of us still suffering post traumatic stress syndrome after taking Chemistry 101 classes) forces the nitrogen in the air to bond with oxygen. This makes something called nitrogen oxides. Nitrogen oxide is a common ingredient in nitrogen-containing fertilizers.

These nitrogen oxides are produced and mixed in the air and when these compounds eventually settle out of the sky or fall out with the rain and thus provide nitrogen to the soil that is in a form that can be utilized by plants. Hey, this is a win-win proposition-the plants are happy and you're happy.

Is there really enough lightning out there to make a difference? Actually, the amount of nitrogen returned to soil is relatively small. Estimates range from 7-10 pounds of nitrogen per acre depending on the region of the country and lightning activity. Compare this to the 100 plus pounds of nitrogen on a per acre basis that is typically applied to maintain a lawn. So no matter how much lightning occurs during the year, you will likely need to buy some type of fertilizer for whatever you want to grow.

Question: I have seen a fertilizer that I am not familiar with called urea. I was told it was a slow release organic fertilizer and better to use than ammonium sulfate (21-0-0). Should I give this fertilizer a try?

Answer: Urea has been around a long time but it is not an organic fertilizer. It is more commonly used for pastures and field crop production and only a few garden supply stores in this area stock urea. While it is available in a slow release form, not all formulations are slow release.

Its fertilizer grade is typically 45-0-0 or 46-0-0. Urea is an excellent fertilizer and contains more nitrogen per bag (45% to 46%) than any other fertilizer available to the home gardener. One drawback is that urea will convert to ammonia very quickly when applied to the soil surface or a grass cover under hot weather conditions. This rapid conversion causes ammonia to be released to the air and not the plant. If you want to try urea, lightly work it into the soil soon after application or apply just before a rain or water in immediately.

Question: We planted an entire new landscape last year that included trees and shrubs. We did not fertilize those plants last year since they where not established. We would like to fertilize this spring. However, we have been told we must rake all the mulch back and put the fertilizer on the bare dirt. Is this true?

Answer: This is the time of the year to fertilize young shrubs and trees. Actually, there is no point in raking the mulch away from the plant to distribute fertilizer whether it is pine straw, hardwood bark, or even brick chips. The fertilizer will dissolve with the first rain or irrigation and move with the water through the mulch and enter the soil.

You may see what appears to be remnants of the fertilizer still on the mulch after several rains. This is filler or carrier material that is mixed with the fertilizer to add bulk. In a 50-pound bag of 13-13-13, only 19.5 pounds of it is actual fertilizer. The remaining 35.5 pounds consists of fillers such clay, fine gravel, etc. Be sure to distribute your fertilizer evenly around the edges of the plant's limbs or what we call the drip line.

Dr. Johnson is a horticulturist with the Galveston County
Extension Office of Texas Cooperative Extension, Texas A&M University. Visit his web site at http://aggie-horticulture.tamu.edu/galveston/index.htm

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