Lawn Questions
When is the best time to apply crabgrass pre-emergent herbicides to lawns in west central Nebraska?
When should I power rake my lawn?
Can you give me some tips on seeding a lawn?
Must I be licensed to apply weed or insect killers to a lawn for pay?
How can I control dandelions in my lawn?
How much water does my Kentucky bluegrass lawn need?
How often should I water my Kentucky bluegrass lawn?
What is causing the grass to turn yellow or die in spots?
Do I need to pick up the clippings when I mow, to prevent thatch accumulation?
Can lawn pesticides be harmful?
When is the best time to apply crabgrass pre-emergent herbicides to lawns in west central Nebraska?
Generally the best time is the last week of April. This is early enough that the soil is too cool for crabgrass and other warm season grasses to germinate, but late enough to prevent most of the herbicide from breaking down prior to crabgrass emergence.
Periodically the weather in March and April is very warm, prompting residents to fear that crabgrass will germinate that early. However, if this were to occur, emerging crabgrass would be killed by hard frosts in March, April and May.
Some long-lasting herbicides, available to lawn care professionals, have longer residual control and can be applied earlier, but most products available to home owners do not last long in the soil.
Remember that herbicides will not begin to control weeds until the weeds begin to germinate. They do not kill dormant seeds.
If the lawn has had a crabgrass problem in the last couple of years, make two applications of crabgrass pre-emergent herbicide; one the last week of April and the second six to eight weeks later, to lengthen the control period (if permitted by the product labeling).
Read and follow pesticide labeling carefully. If the labeling conflicts with this information, follow the labeling.
When should I power rake my lawn?
Actually, a better question is, "Should I power rake my lawn?"
Routine, yearly power raking is seldom necessary and is not advisable. Power raking appears to pull up a lot of thatch, but really is not as effective as it appears. The real problem, though, is that it damages roots and stresses the grass.
So before power raking, determine that your lawn really needs it. Sample for thatch in several spots in the lawn. If the thatch layer is over half an inch thick, power raking may be advisable. If it is half an inch or thinner, do not power rake. The turf needs some thatch to provide protection from wear, and protection from temperature extremes.
While routine power raking is not recommended, routine core aerifying (plugging), if done properly, is usually a good idea. Plugging combats compaction and can reduce the tendancy of thatch to develop.
The best time of year to core aerify a Kentucky bluegrass lawn in Nebraska (or power rake, if necessary) is in September. The second best time is in April.
For more information go to IANR Publications--Horticulture and click on "Thatch Prevention and Control" (under "Turf"). Also refer to the other resources listed on the IANR Publications--Horticulture page.
One last thought: Do not use the "power rake" attachments meant to fit on the shaft of a rotary lawn mower (the regular type homeowners use) in place of the blade. They can cause serious damage to the turf.
Can you give me some tips on seeding a lawn?
Following are a few tips to help you be successful:
- Usually fall is a better time to seed a cool season lawn than is spring. The soil is warmer in September than in April, so the seed will germinate more quickly, and usually weed problems are much lower in the fall. In addition, spring seeded grass has a very shallow root system when hot summer weather arrives, so keeping it alive an healthy can be challenging.
- Remember to keep the soil moist until the grass emerges and has a couple of inches of growth, then gradually reduce watering frequency. If you plant a mixture of Kentucky bluegrass and perennial rye, remember that the perennial rye will emerge faster, so be patient for a little longer while waiting for the Kentucky bluegrass to emerge.
- You may be able to overseed instead of starting over. However, if your stand of grass is 50 percent, you have a lot of problems with diseases and need to change to newer, disease tolerant cultivars, or have serious weed problems, it is probably better to start over.
- Spread about 1.5 bales of clean straw over the newly seeded lawn for every 1000 square feet. Use enough straw to shade the ground, but not so much that you can't see the soil surface between strands of straw. The straw will reduce the frequency of watering required in establishing your lawn, by reducing evaporation. Excessive straw will pack down and prevent grass emergence and establishment.
- Avoid mixtures that contain annual rye. It emerges quickly but takes up space from the other grass, and it will die the first winter.
- Avoid mixtures that contain more than about 20 percent perennial rye. It emerges quickly and may be helpful in shading the soil while the Kentucky bluegrass emerges, but it will die within the first few years. In that time the Kentucky bluegrass should have filled in if it was the dominant grass.
Must I be licensed to apply weed or insect killers to a lawn for pay?
Yes - In order to apply any pesticide for pay, to a lawn or ornamental area, you must be at least 16 years old and licensed as a commmercial pesticide applicator. This is true regardless of whether the pesticide you are using is a restricted-use or a general-use product.
Pesticides include weed killers (herbicides), insect killers (insecticides), fungicides, rodenticides, etc. The law also applies to fertilizers that contain herbicides (crabgrass preventers, for example) and fertilizers that contain insecticides.
For more information contact your University of Nebraska Cooperative Extension office, or call the Nebraska Department of Agriculture Bureau of Plant Industry at (402)472-2394 or 1-877-800-4080.
How can I control dandelions in my lawn?
If you don't have too many dandelions, dig them. The forked dandelion diggers available in stores work well. Cut the root at least an inch and a half below the soil surface to prevent grow-back.
If you have too many to dig, go ahead and spray (following product labeling carefully), but don't expect extremely good control when spraying in the spring.
To understand that last statement, you need some background information:
Dandelions are tough perennial weeds. Although they are most obvious in April and May, when they bloom, they live throughout the year, and can continue to live and grow for several years. In spring their energy goes into flower and seed production, but in the fall a large part of their energy goes toward moving sugars and starches into the root for winter storage; so herbicides are carried to the root in the fall more effectively than at other times of the year.
Unfortunately, a lot of people forget about their dandelions in the fall. Don't be one of them. If you intend to control your dandelions with herbicides, spray in the fall. Your lawn will look much nicer the next spring. October is the prime time to zap dandelions.
One last bit of information: The "weed and feed" fertilizer granules are generally not as effective in controlling dandelions and other broadleaf weeds as the liquid sprays.
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How much water does my Kentucky bluegrass lawn need?
University of Nebraska specialists recommend an inch of water a week in spring and fall. That can be applied in the form of precipitation or irrigation. If it rains, great! You can put off watering. In summer the lawn will need about 1.5 inches per week due to higher evaporation rates.
How often should I water my Kentucky bluegrass lawn?
In spring and fall, Kentucky bluegrass has a deeper effective root system, so deep, infrequent watering is the best strategy. On a regular loam soil a reasonable practice is to water once a week, applying an inch each time (in absence of precipitation). If your soil is clayey and takes water very slowly, you may need to water a while, shut off the sprinkler for an hour, then water so more.
Couple these guidelines with common sense. For example, if we have a week of rainy weather, you may not need to water again for one to three weeks, especially if the grass grows slowly in the meantime.
In the heat of the summer, Kentucky bluegrass has a shallower effective root system, so apply your weekly 1.5 inches in two or three applications, applying half to three quarters of an inch each time. Again, take precipitation into account.
If your soil is very sandy you will need to water more often, applying less water each time.
How long should I run my sprinklers?
You will have to answer that one yourself. It depends on your water pressure and the type of sprinkler you have. Set some tuna or cat food cans out and collect water to determine how long it takes for your sprinklers to apply half an inch of water.
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What is causing the grass to turn yellow or die in spots?
Turf can yellow or die from many different reasons, ranging from compaction or animal urine to fungal diseases or insect infestations. Please refer to the "Turf Troubleshooting Reference" listed under "Publications" (along the narrow black bar directly above).
Do I need to pick up the clippings when I mow, to prevent thatch accumulation?
Not as long as you mow regularly and the grass does not become too tall between mowings. Grass leaf blades contribute little to thatch. Thatch consists of dead tissues, especially roots and stems. Generally, leaves decay rapidly rather than building up appreciably in the thatch layer.
Clippings left on the surface decay rapidly, returning nutrients to the soil.
The main exception is that the first mowing of the season is recommended to be short and the clippings removed at this mowing.
For more information go to IANR Publications--Horticulture and click on "Thatch Prevention and Control" (under "Turf"). Also refer to the other resources listed on the IANR Publications--Horticulture page.
Can lawn pesticides be harmful?
Yes!
Pesticides are sometimes applied at rates higher than the labeled rates, or used more often than allowed on the label. This not only is illegal, but can damage the lawn and adjacent flowers, trees and shrubs.
Pesticide spray drift is a common problem, resulting from application in windy weather. Some pesticides are prone to vapor drift, even when the air is relatively calm. This is especially so in hot weather.
Hackberry and linden trees are particularly sensitive to herbicide drift and herbicides in the soil. Other trees, shrubs and ornamental plants can also be damaged.
Overuse of pesticides can result in loss of important microorganisms, earthworms and other beneficial organisms from the soil. As a result, thatch can build up more rapidly and trees and shrubs may not grow as well.
Minimize the negative effects of pesticides in the following ways:
- Never apply a pesticide unless you know the identity of the weed, insect or other pest you desire to control. Otherwise you cannot make intelligent choices about which product to use, when to apply it, alternatives to pesticides, etc.
- Allow beneficial organisms to control your pests, if possible, instead of using pesticides: lady beetles, lacewings, ground beetles, beneficial mites and wasps, etc.
- Follow recommended practices to keep plants healthy: mulching, watering properly, etc. Healthy plants are less likely to be attacked by harmful insects and diseases.
- Apply pesticides at the correct time or the effort may be a waste of time and money at the expense of the environment.
- Avoid spraying dandelions in the spring. Spring applications are not very effective against dandelions anyway. To make matters worse, trees and shrubs are particularly sensitive to pesticides in spring.
Most older youth or adults in good health can dig up to 1,000 dandelions in a yard, 100 at a time, in several shifts over a few days. If you have some willing, able bodied helpers, you can takle larger projects! Be sure to cut the root at least 1.5 inches deep. A knife will work, but a pronged digger is better. Diggers are available at garden centers.
If you still have a dandelion problem in the fall, spraying a weed killer at that time can be very effective. This is the time the weeds are moving sugars and starches to their roots for winter storage, so this is the time herbicides will move into the roots most readily. Use a liquid product and spray in late September or in October.
- Follow pesticide labeling carefully. Never apply a pesticide that is not labeled for the plant and site. Always pay special attention to precautions regarding wind, hot weather, sensitive plants, etc.
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