Curtis Swift

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October 18, 2012
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SWIFT: Last-season fertilization beneficial to turf health

David blew out my sprinkler system on Tuesday. If I had been more on the ball I would have made one last application of fertilizer to my lawn before he accomplished that task. Now I'm going to have to drag a hose to water the fertilizer in.

I'm not blaming David because I was certainly provided sufficient warning he would be by to winterize my irrigation system. I'm irritated at myself for not getting the fertilizer applied before he pulled up with his air compressor to do the job I had asked him to do.

For those of you who haven't yet had your sprinkler systems winterized for the season, I would encourage you to remember to have that done. If you are on domestic/potable water you may have already had your system winterized. Most of the Grand Valley Irrigation water providers will be turning the water out of the ditch on Oct. 23 so you may not have your system winterized until after that date. Try to fertilizer your lawn before irrigation water is no longer available otherwise you will need to drag a hose. That's what I'm going to do. The fertilizer needs to be watered. A quarter- to half-inch of water is sufficient.

Up to two pounds of a fast-release nitrogen product should be applied per one-thousand square foot of your lawn. I'll be using ammonium sulfate. This is 21% percent nitrogen, so I will be applying 9.5 pounds of ammonium sulfate per 1,000 square foot area of my lawn. If you are using organic products, this late-season fertilizer program will not work for you as you need a fast-acting product like ammonium sulfate. A recent caller argued that to apply this amount of fertilizer this late in the season was wrong. "They don't do this back East so it isn't necessary in Colorado" was the gist of his argument. I don't know what he meant by back East but university researchers in Ohio, New England, the Midwest, the mid-Atlantic region, and the Pacific Northwest have shown late-season fertilization is beneficial to turf health.

In addition to the fall fertilization of your lawns, problems with trees and shrubs could be identified and possibly corrected this fall. Dead branches and hazardous and diseased trees should be identified, marked, and pruned or removed to prevent them from breaking and falling this winter. Insect problems could be identified and possibly even treated to protect plants from the damage they will be causing next year. The black vine weevil, the hackberry nipple psyllid, and various honey locust leaf insects are examples of some of the insects that benefit from a fall treatment. Waiting until spring when your plants are exhibiting the damage caused by these and other pests is too late. The black vine weevil is a pest identified by the notching of the leaves by the adults. The major damage, however, is to the roots due to the feeding of the grubs. The root damage creates opening through which pathogens can invade and cause stem and root rot. Treatments made now will help control these grubs and reduce the chance of attack by these pathogens. Black vine weevil-free plants have a greater chance to develop roots in early spring increasing their chance of a full recovery. Other insect pests can also be controlled by a fall application of an insecticide.

Identifying weed problems in the fall will provide you more control options. Some weeds are best controlled in the fall while others prefer spring treatments. Without knowing what the weeds are, you won't be able to develop a plan of action for their control.

We all know the height of cut of our lawns going into the winter directly affects the health of next year's lawn. Too high and we end up with disease problems; too low and the roots and crowns suffer from dehydration. How your lawn is edged also affects the health of the lawn and weed infestations you will have to deal with next year. This past Tuesday I drove by a lawn that was being edged using a string trimmer. The angle of the cut used to trim the grass was incorrect and is going to result in a weak grass, increased disease problems, and increased weed development along the sidewalk. The resulting weeds and diseases will likely spread into the lawn causing further problems for the property owner. A simple change in the angle of the string would have prevented this disease and weed infestation.

Fall is a great time to develop a plan to protect your lawn and gardens from insects, diseases and weed infestations. Take the time to walk your property and identify as many of the problems as you can. Your next task is to come up with a plan that takes into account all the problems you were able to locate. Once you have the plan put together, you will be much closer to having problem-free lawns and gardens in 2013.

Dr. Curtis E. Swift is a retired horticulture agent with the CSU Extension. Reach him at or check out his blog at He owns Swift Horticultural Consulting and High Altitude Lavender.

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The Post Independent Updated Oct 18, 2012 03:29PM Published Oct 18, 2012 03:27PM Copyright 2012 The Post Independent. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.