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Turfgrass Management: Frequently Asked Questions
 Remember that these questions and answers are specific to the State of Alabama.  Many of these answers do not apply to other areas of the country, especially outside the Southeast.




Which grasses will grow in Alabama?


     Grasses used in Alabama can be divided in to two groups: warm season grasses and cool season grasses.  As their names imply, warm season grasses are adapted to hot weather and are usually native to tropical or sub-tropical environments.  They go dormant in the winter and turn brown.  Cool season grasses are better suited to cool weather and are usually native to temperate areas.  They remain green all winter long.

   Most of the grasses used for turf in Alabama are warm season grasses.  In north Alabama, some species of fescue (especially tall fescue) are used for permanent lawns.  Creeping bentgrass is used on golf courses for putting greens in the northern half of the state.  Ryegrass is used to overseed warm season grasses in the winter.  This provides a green color when the wearm season grass is dormant.

   One grass which is not suitable for use in Alabama is Kentucky bluegrass.  Although this is the most popular grass nationwide because of its great appearance, it does not have the heat resistance to stand up to Alabama summers.  

   In the summer of 2005, newer heat tolerant bluegrasses have come on the market for use in the Southeast.  These are the results of breeding Kentucky bluegrass with other bluegrasses, essentially incorporating heat tolerance into a grass that looks like Kentucky bluegrass.  They are usually sold as blends with tall fescue, and should be successful in areas where tall fescue can be grown.  They may not survive well, however, in southern Alabama.

Warm Season Grasses

Cool Season Grasses
Bahiagrass
Bermudagrass
Carpetgrass
Centipedegrass
St. Augustinegrass
Zoysiagrass
 Creeping bentgrass (golf courses only)
Creeping red fescue
Ryegrass
Tall fescue
Heat tolerant bluegrass

-David Han, Assistant Professor / Extension Specialist, Turfgrass Management

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Which turfgrasses like shade?


     The short answer is none.  All grasses are best adapted to high light levels - that means sunshine.  Although there are some grasses which can tolerate shade better than others, the key word here is tolerate.  All things being equal, grasses will do better in full sun than in shade.

     The best shade-tolerant warm-season grass is St. Augustinegrass.  But you will not see sod farmers planting trees or putting up shade tents on their fields of St. Augustinegrass; even it grows fastest in full sun.  Centipedegrass and zoysiagrass have less shade tolerance and bermudagrass still less.  Bermudagrass needs full sun for best quality; if there is any doubt about shade, use zoysia, centipede or St. Augustinegrass instead.  Of course, there are differences in the shade tolerance of different varieties of each species, but there hasn't yet been a bermudagrass variety as shade tolerant as any St. Augustinegrass, and I doubt there ever will be.

     Cool-season grasses are generally more shade tolerant that warm-season grasses.  However, the only cool-season grasses that will survive Alabama summers on a regular basis are tall fescue, fescue blends, and fescue / heat-tolerant bluegrass blends.  These are restricted to the northern half of the state as they have limited heat tolerance.  

     If you have an area that receives less than 50% sun, it may be time to consider some other ground cover than grass.  Mondograss, English ivy, mulch, gravel or pine straw are some alternative ground covers for shady areas.

-David Han, Assistant Professor / Extension Specialist, Turfgrass Management

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How often should I mow my lawn?


Mowing a lawn frequently enough is one of the simplest yet most effective ways to ensure its health.  People often forget that the lawnmower is one of the best weed control tools available.  A lawn that is mowed often enough - and with a sharp blade - not only looks better but is healthier.

     The rule of thumb for mowing is to mow often enough that you cut off no more than a third of the grass at any one time. For example, if your mower is set at 2 inches, mow before the grass gets above 3 inches tall, so you are only cutting off one inch, or a third of the total height.  This will ensure that the grass isn't shocked too much by mowing.  It also minimizes the potential for scalping and if you mow often enough, the clippings don't need to be caught under normal circumstances.Scalping can destroy the appearance of a lawn

     The interval between mowings depends on the height of cut and how fast the grass is growing.  The lower the mowing height, the more often you will have to mow.  As everybody knows, you will have to mow more often in the summer, when the grass is growing the fastest.  Different grasses have different growth rates.  Bermudagrass should be mowed much more frequently than zoysiagrass, for example.



-David Han, Assistant Professor / Extension Specialist, Turfgrass Management

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Scalping can make a beautiful lawn look ugly

How high should I cut my lawn?


   The optimum mowing height varies among the different species of turfgrass.  As noted above, the interval between mowings depends on several factors, mainly height of cut and the growth rate.  The lower you sut, the more often you will have to mow.  A lawn's growth rate is affected by many factors, including fertilization, rainfall or irrigation, and grass species.  Here are recommended mowing heights for the most commonly used lawn grasses in Alabama, along with a rough estimate of a typical interval between mowings:

Turfgrass

Optimum Mowing Height (inches)

Typical Mowing Frequency (days)

Mower Type
Bahiagrass
 2 to 4
 7 to 10
 Rotary
Common Bermudagrass 
 1 ½  to  2 ½
 5 to 7
 Rotary
Hybrid Bermudagrass
 1 to 1 ½
 3 to 5
 Rotary or Reel**
Centipedegrass
 1 to 1 ½
 7 to 14
 Rotary or Reel**
Ryegrass
 2 to 3
 7 to 14
 Rotary
St. Augustinegrass
 2 ½* to 4
 7 to 14
 Rotary
Tall Fescue
 2 to 3 ½
 7 to 14
 Rotary
Zoysiagrass
 1 to 2
 7 to 14
 Rotary or Reel**
* Dwarf St. Augustinegrass varieties only
** Reel mowers provide a better quality cut and are needed for heights below 1 ½ inches, but powered reel mowers can be much more expensive to buy and maintain than regular rotary lawn mowers.

-David Han, Assistant Professor / Extension Specialist, Turfgrass Management

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How should I fertilize my lawn?
 

   With so many climates and so many grasses used in Alabama, it is difficult to give blanket recommendations.  In order to properly fertilize your lawn, it is important to know what kind of grass you have (or wish to have).  If you need help identifiying the grass in your lawn, contact your local Extension office.

   There are some basic rules of thumb to fertilizing a lawn.  For warm season grasses (the majority of grassed grown statewide, including bermudagrass, centipedegrasss, St. Augustinegrass and zoysiagrass), the time to fertilize is in the summer.  One of the most common mistakes people make is fertilizing too early in the spring.  If there is a late frost, the new growth stimulated by an early fertilization can be killed, effectively wasting that fertilizer application.  For this reason, it is a good idea to wait until after all danger of frost is past before fertilizing your lawn.  In some areas of the state, this can be mid-April or later.  So to be conservative, I do not recommend fertilizing lawns until May.  Of course, if you are in a warmer part of the state, this may be adjusted by a few weeks.

   Cool-season grasses like tall fescue or winter ryegrass should be fertilized mainly in the fall.  For tall fescue lawns, a small spring fertlizer application may be made, but do not apply too much nitrogen in the spring.  Het-tolerant bluegrasses may require more fertilizer in the spring and fall than tall fescue.  Current reserach will dettermine optimal fertility for the new heat-tolerant bluegrasses.

   The following table gives recommended guidelines for nitrogen applications on home lawns.  For recommendations on phosphorus and potassium, you should have a soil testing laboratory analyze your lawn's soil.  Your local Extension office can tell you how to take samples for soil testing and send them to the lab for analysis.
Turfgrass Desired Qaulity
 Total Pounds of nitrogen per 1000 square feet per year
 Total pounds of nitrogen per 1000 square feet per month

Jan.
 Feb.
 Mar.
 Apr.
 May
 Jun.
 Jul.
 Aug.
 Sep.
 Oct.
 Nov.
 Dec.
Bahiagrass
 Low
High
 2
3



1
1

1
 1
1



Common Bermudagrass
 Low
High
 3
4



1
1
 1
1
1
 1
1



Hybrid Bermudagrass
 Low
High
 3
5



1
1
 1
1
1
 1
1
1


Centipedegrass
 Low
High
 0
1




1/2

1/2




Ryegrass*
 Either
 2
1/2






1
 1/2
 1/2
St. Augustinegrass
 Low
High
 3
4



1
1
 1
1
1
 1
1



Tall Fescue
 Low
High
 2
4

1/2
1





1
1
 1/2
1
1
Zoysiagrasss
 Low
High
 3
4



1
1
1
 1
1
 1
1



*Ryegrass is used as an overseed to provide green color in winter


-David Han, Assistant Professor / Extension Specialist, Turfgrass Management

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Should I catch my clippings?


     If you follow the mowing guidelines above and mow often enough, no.  Clippings will not contribute to thatch buildup, nor will they clump up and suffocate the grass underneath if you mow often enough.  

There are exceptions to this rule of thumb.  If you have to mow when the grass is wet - which we do not recommend - and the clippings clump up, you should remove them.  Also, you should catch your clippings if your lawn has a disease problem, such as dollar spot, rust or leaf spot, that could be spread by infested clippings.

-David Han, Assistant Professor / Extension Specialist, Turfgrass Management

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What is thatch?


     Thatch is the layer of dead and living plant parts in between the green canopy and the soil.  Thatch is mostly made up of stems, with some roots and very little leaf tissue.  One of the more common misconceptions about thatch is that it builds up when clippings are not removed during mowing.  In fact, it is the rhizomes and stolons that contribute the most to thatch.  

     Thatch builds up when new plant material is produced faster than old, dead material can be decomposed.  It is a bigger problem in very dense or fast-growing turf because stems and roots build up faster than in thin or slow-growing turf.  Thatch also is a bigger problem when the soil is compacted or poorly drained, because these soil conditions decrease activity of microbes that break down thatch.  Having some thatch is ok. It can cushion the lawn and help to moderate soil temperature and moisture changes.  However, too much thatch (more than 1/2 inch) causes many different problems.Photo of heavy thatch  

     If there is excessive thatch, the grass roots can start growing in the thatch instead of the soil.  This exposes them to cold air in the winter and has been shown to increase winter kill.  Thatch also does not hold as much water as the soil and grass with roots mostly in the thatch is not very drought tolerant.  Too much thatch is a good habitat for many disease and insect pests.  It can also impede the flow of water down into the soil.  If the lawn is too spongy from excessive thatch, the mower may sink into it and scalp while mowing.

     If you have too much thatch, there are several thatch management techniques that can help get it back to a desirable thickness.

-David Han, Assistant Professor / Extension Specialist, Turfgrass Management

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How do I manage thatch?


     The basic thing to remember when managing thatch is that too much thatch is the result of new plant material being produced faster than old stems are broken down by the soil microbes.  Preventing excessive thatch means reducing the rate of thatch production and also speeding the rate of thatch decomposition.

     You can reduce the rate of thatch accumulation by not fertilizing too much.  Follow the recommended fertilizer rates and timings for your particular lawn grass.  Irrigate lawns infrequently but deeply to encourage deep root growth.  Be sure to mow often enough.  

     You can speed the rate of thatch decomposition by making sure the soil is conducive for the growth of beneficial microorganisms.  Core aeration is often needed on home lawns to relieve soil compaction.  Maintain a near-neutral soil pH.  Light topdressing - adding a thin layer of soil or sand to the top of the lawn - can stimulate the growth of thatch-decomposing microbes.  The key word here is light.  The ideal topdressing is only 1/8 - 1/4 inch.  Adding more topdressing can wreck the soil by creating layers that block the movement of water down into the soil.

     If thatch has built up deeper than 1/2 inch, it is necessary to remove it mechanically.  Everything from hand raking it out to powered dethatching equipment will work.  Many rental centers rent dethatching equipment and many lawn care companies provide this service.  Dethatching is hard on the lawn - the thatch is physically torn out of the grass and it will take some time to recover.  For this reason, dethatch when the grass is growing rapidly and can recover.  For warm-season grasses, this means early summer is the best time to dethatch.

-David Han, Assistant Professor / Extension Specialist, Turfgrass Management

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