Weekly Express-News Article

By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist

Saturday, September 20, 2008

“Fall Lawn Tasks”

             It is time to fertilize the lawn for autumn.  Fall fertilization contributes to cold survival and fast green-up in the spring.  The nutrients are taken up by the grass plant and organized for both use.

 

            Seek out a fertilizer that is labeled “Winterizer.”  The title indicates that it has a high level of available nitrogen and potassium.  Phosphorous is less necessary in our soils, but some “winterizers” do include phosphorous.

 

            The formula is often in a 3-1-2 or 3-0-2 ratio such as 18-6-12, 15-5-10, or 10-0-5.

 

            The first number is the percentage of nitrogen in the bag.  It is the key nutrient and what you pay for.  If alternate fertilizers are available, select the one that is the best value for available nitrogen.  Multiply the percentage times the weight of the bag and divide that number into the cost.  For example, a 40 lb., bag of 10-0-5 fertilizer would have 4 lbs., of nitrogen.  If the bag was $16, the nitrogen would cost $4/lb.  If the 40 lb., bag was 15-5-10, and it was $40 for the bag, the cost would be $5 per lb., of nitrogen (15% x 40 = 6 lbs., $30 ÷ 6 lbs., = $5/lb.).  The 10-0-5 would be the best bargain.

 

            Most recommendations call for 1 lb., of nitrogen per $1,000 square feet of lawn.  The 10-0-5 fertilizer would require 10 lbs., of the material to apply 1 lb., of nitrogen.  It would take 7.5 lb., of the 15-5-10 fertilizer.  In most cases, the lowest recommended rate in the bag is 1 lb./1,000 feet of nitrogen. 

 

            It is not too late to apply a pre-emergent herbicide to prevent winter weeds.  Use XL or Amaze to prevent annual blue grass, rescue grass, and rye.  For dandelions, bedstraw, thistles, and henbit, apply a product that lists the weeds you want to control.  The pre-emergent needs to be applied as soon as possible because those weeds germinate with the first cool weather that arrives.  Follow the instructions on the bag precisely for the most effective results.

 

            With the dry weather we have experienced drought damaged areas on the lawn in the hottest areas.  They will be in full sun along driveways or sidewalks. 

 

            Dry areas can also occur under trees and at areas where soil depth is reduced because of compaction  or a boulder underlies the grass. 

 

            The trees compete with the lawn for water and in shallow soils the lawn may suffer.  Boulders or compacted areas in the soil limit root growth and water storage in the soil, so the affected lawn dries out faster.        

 

To address these “hot spots,” give them some extra water.  Hand-watering after work a couple of evenings per week may help you unwind and it will green-up the dry spots in the lawn.  For those long strips of dry areas along driveways or sidewalks, consider laying a leaky hose.  The hose can be removed and special watering ended when we escape our 90° F temperatures.

 

            If the dry areas do not respond to the special watering your lawn may have chinch bugs.  The tiny sucking insects feed on grass blades in the hottest part of the lawn.  To kill chinch bugs, apply one of the soil insecticides.  They are available in granular form  at your favorite nursery. 

 

            The same granules kill grubs.  Now is not the best time to kill grubs, but you can save the remaining granules for application next May if your lawn is infected with grubs.