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PESTICIDE-FREE LAWNS

Lawns without herbicides, insecticides & chemicals

By: Sandy Feather ©2011
Penn State Extension


Q. I've been reading more and more articles about the dangers of pesticides used to control weeds and bugs on home lawns. Can you recommend some practices that will allow me to have a decent lawn without using pesticides? I am especially worried about having all those chemicals around my pets and children.

A: Proper cultural management of your lawn will go a long way toward improving its health and appearance without using pesticides on a regular basis.


It begins with Mowing

Mowing practices greatly determine the quality of lawns. Allowing a lawn to grow too tall and then cutting it short is stressful to grass. It uses a tremendous amount of its stored energy reserves to push out new growth after such treatment. The general rule of thumb is not to remove more than one-third of the leaf blade at one time. Rather than mowing on a schedule – say, every Saturday – mow as the grass’s growth dictates. That may be twice a week during the cooler weather in spring and fall, or every few weeks during hot, dry summer weather (especially if you do not water).

Proper Mowing Height

Most species of turfgrass should be cut at a height of two-and-a-half to three inches. There is a direct relationship between the height of cut and the depth and extent of the root system. The longer the grass grows, the more extensive its root system; the shorter you cut it, the less root system it will have. Summer heat and drought are more stressful for our cool-season grass species than winter cold. Keeping the grass a little taller encourages an extensive root system that will make your lawn more drought-tolerant. It also shades the soil, moderating soil temperatures and helping to conserve soil moisture as well as shading out germinating weed seeds that try to become established.

lawn spreader and sprayer combined
Lawn care company applicator

Be sure to sharpen your mower blade regularly. A sharp mower blade makes a clean cut that the grass recovers from easily. Dull mower blades shred the grass, making jagged wounds that are harder to heal. They can serve as a point of entry for insect and disease problems. How often you sharpen your mower blade depends on the size of your lawn and the number of obstacles it is likely to encounter. Monthly sharpening for large lawns is not unreasonable; smaller lawns can get by with once a year.


2nd Most Important is Proper Fertilization

Next to proper mowing, appropriate fertilization is important to encourage a dense, well-rooted stand of lawn grass able to resist pests and environmental stress. Inadequate or excessive fertilization can make the lawn more susceptible to disease and insect problems and less tolerant of summer stress.

Soil Tests Eliminate Guessing

A soil test will help you design a fertilization program that provides what your lawn needs for optimum health and growth.  It will also tell you what you have to do to get your soil pH (acidity or alkalinity) into the optimum range of 6.5 to 7.0 that most lawn grasses prefer. Soil test kits are available from your local Penn State Extension office for a nominal fee. In Allegheny County, consumer soil test kits cost $12 each, and come with detailed instructions for taking a good soil sample and information to help you understand your soil test results. Customers ordering multiple kits at one time pay $9 each for the additional kits. Send a check made payable to Penn State Extension to Penn State Extension, 400 North Lexington Street, Pittsburgh, PA 15208. Write Attn. Soil Test Kit in the lower left corner of the envelope.


Fertilizer Timing

Typically, late spring (mid- to late May), late summer (late August to mid-September) and late fall (mid-November) are the best times to apply fertilizer.  Fertilizing in late spring supports the increased root and shoot growth typical in spring, while the late summer-early fall application helps the lawn recover from summer stress and supports increased root and shoot growth that will return with cooler weather and rain. Once the grass is no longer pushing top growth, but before the ground freezes, it is time for the final application. This last application supports root growth that will continue until soil temperatures fall below 40 degrees. All fertilizer applications should be made when there is adequate soil moisture. Since plants take up nutrients in water, there is no point in applying fertilizer to bone dry soil.

uneven fertilizer application
Uneven application resulted in "skunk stripes"

Liming is best done in fall. Limestone moves through the soil very slowly and takes time to effect the desired change in pH. If your soil test reveals that your lawn needs 100 pounds or more of limestone per thousand square feet, break it into two applications, fall and spring.


Lawn Irrigation

Watering your lawn when we get into hot, dry summer weather is a personal choice. It is fine to allow your lawn to go dormant. An otherwise healthy lawn can go about six weeks without rain; it will turn brown, but should recover when cooler temperatures and rain return. If you choose to water, make sure you do so properly in order for the lawn to benefit from it as much as possible.

 

Established lawns benefit most from deep, infrequent watering that encourages a deeper, more extensive root system. Conversely, frequent, shallow watering encourages a shallow root system. A shallow root system means a lawn that is under drought stress when the top inch of soil dries out. Use a sprinkler or an irrigation system to apply one inch of water weekly to your lawn when rain is minimal. This is best applied in one long, deep soaking session, rather than watering your lawn a little bit every day. Our clay soils can only absorb about one-half an inch of water an hour, so it should take two hours of watering to apply an inch of water. To determine how long you have to run your sprinkler or irrigation system, take a flat-bottomed container such as a coffee can and mark off half-inch increments. Place the can or cans where it will be hit by the water, and time how long it takes to gather one-half inch of water. Then run your sprinkler twice as long. You may need to apply water even slower to steep slopes to avoid wasting water to runoff.

When to Water your Lawn

It is best to water in the morning. If you water during the heat of the day, too much water is lost to evaporation. If you water at night, the grass stays wet too long, which can result in more disease problems.
 


Thatch Problems can become Serious

You should also check your lawn for thatch. Older lawns often suffer from a deep thatch layer. Thatch is nothing more than a layer of organic matter between the soil surface and the crowns of the grass plants. Dig up a small square of turf so you can look at the soil profile. The thatch layer is easily visible. Thatch is created when growing turfgrass sloughs off dead stems and roots. A thin layer of thatch - one-half inch or less - is desirable. It acts as a mulch, moderating soil temperature and maintaining soil moisture. More than that creates problems, though. A thick layer of thatch can keep water from reaching the soil, so your lawn is constantly drought-stressed. And that creates more thatch. Thatch can also be a breeding ground for insect and disease problems. Even worse, if your lawn does develop a problem with white grubs (soil dwelling-insects that feed on turf roots), a thick thatch layer can make it very difficult to get an insecticide down to where the grubs are feeding. The causes of thatch include:

  • The variety of grasses in your lawn. Bluegrass and creeping red fescue are the worst thatch formers of the cool season lawn grasses.

  • A soil pH lower than 6.5 immobilizes the microbes that break down thatch.

  • Over-fertilizing your lawn.

  • Frequent, shallow watering.

  • Allowing grass to grow too tall, and then cutting it short and not collecting the clippings.

A moderate layer of thatch - between one-half and one inch - can be removed by dethatching your lawn with a power dethatcher. Dethatching is very stressful and should only be done in fall. You can rent dethatchers, or hire a lawn service to do it for you. Run the dethatcher in one direction, and then go over you your lawn in the perpendicular direction. A good dethatching job should make you want to cry when you look at your lawn. Topdress the lawn with a thin layer (one-eighth to one-quarter inch) of good compost, then overseed with varieties of turfgrass that match your existing lawn to help it recover.

aeration core
Up to ˝-inch of thatch is OK

If you have over one inch of thatch, consider a total renovation - removing your existing lawn and starting over. The knives of most dethatchers will not go deep enough to get through the thatch and down to the soil, which is important for a good dethatching job. A good dethatching job is a lot of hard work, but will not be very effective if you have over an inch of thatch.


Aeration Helps A Lawn Breathe

If you do not have a thatch problem, but the soil is compacted, rent a core aerator. Again, they are available from many tool rental shops, or you can hire a lawn service to do the aerating for you. Core aerators pull three to four inch plugs of soil out of the ground and leave small holes behind. This helps aerate the soil and alleviate soil compaction. Fall is ideal for core aeration (just before applying limestone) but it can be done in the spring as well. If your lawn does not have a lot of activity on it, core aeration every three years or so will keep the soil aerated sufficiently. If all the neighborhood kids play in your yard, consider yearly core aeration in late fall to reduce soil compaction as much as possible. You can break up the cores with a rake or allow them to stay on the lawn where they will break up during winter’s freeze-thaw cycles. If they are creating too much of a muddy mess (when children and/or pets play on the lawn), you can rake them up and put them on the compost pile.

thick thatch layer on a lawn
Heavy thatch and grubs destroyed this home lawn

Topdressing with compost after core aeration is a good tool to slowly improve the quality of the soil under your lawn without tearing it up and starting over. A lawn is only as good as the underlying soil. A six to eight-inch base of topsoil that contains a moderate amount of organic matter is ideal, but few lawns have that luxury.

As a matter of fact, yearly topdressing with a thin layer of compost followed by overseeding is one of the most important tools to maintaining a healthy, attractive lawn without using pesticides. Keep a bag of grass seed on hand so you can fill in bare spots whenever they occur so that grass fills in, rather than weeds. Those spots will have to be kept moist until the seed germinates and the grass fills in, especially during hot summer months.

 MORE

Using pesticides

Integrated Pest Management

Iris Borer

 

    


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