The Book On KBG

grass1950August 1, 2013

Credit and appologies to Texas_Weed for plagerism and following his lead, but some concepts are just darn good ideas and some facts are, well, facts.

What follows is a generic calendar of recommended lawn care practices designed to help you care for a Kentucky Bluegrass (KBG) lawn. Please understand this is generic and time tables may have to be adjusted for you geographical location.

With the exception of "organic", the use of the term "fertilizer" means synthetic fertilizer, either slow or fast realeae will do with the excetion of the last fertilizer of the season= urea 46-0-0, which, to my knowledge, is only available as fast release and is applied with that property a priority.

March through May


Mow when it first turns green or when you first notice growth as the grass comes out of Winter dormancy with the mower set at 2 to 2 1/2 inches. Mowing at his height will encourage KBG's early prolific Spring rhizome and spreading ability.
Practice mulch mowing, aka grass re-cycling, which means simply leaving grass clippings on your lawn. Grass clippings decompose quickly and can provide 1 percent of the total weight of the clippings in additional nitrogen and potassium and another .4% of the clippings weight in phosphorus That can be 25% or more of the lawn's fertilizer needs. If prolonged rain or other factors prevent frequent mowing and clippings are too plentiful to leave on the lawn, they can be collected and used as mulch.


Apply 1 pound of nitrogen per thousand square feet around May 30- June 1st. This will supply nutirient needs of the grass into the heat of Summer and allow the grass to store carbs for survival during Summer dormancy. Use a complete nitrogen-phosphorus-potassium (N-P-K) turf-grade fertilizer with a 3-l-2, 4-1-2, triple 12 or triple 19 ratio (for example, 15-5-10, 20-5-10. 12-12-12, or 19-19-19). Let a soil test be your guide to select a proper ratio of NPK to adjust for any deficiencies.
To determine the amount of product needed to apply 1 pound of' nitrogen per thousand square feet, divide 100 by the first number in the fertilizer ratio. For example, for a 20-5-10 product, divide 100 by 20. The result is 5.0 pounds of product per thousand square feet.

Weed Control

Apply pre-emergence herbicides to control crabgrass, goose grass, foxtail, etc by the time the forsythia are in full bloom.


In many of the areas in which KBG grows best (temperature zones 4,5 and 6), Mother Nature will often take care of the irrigation needs of KBG in the Spring; however: water should be present to a soil depth of 4 to 6 inches. Probe with a screwdriver to determine moisture depth. KBG needs a weekly application of about 1 to 1 1/4 inches of water. On sandy soils it often requires more frequent watering, for example, 1/2 inch of water every third day. It may be necessary to irrigate an area for 3 to 5 hours to apply 1 inch of water. (It requires 640 gallons of water to deliver 1 inch of water per thousand square feet.) Because clay soils accept water slowly, irrigate just until runoff occurs, wait 1/2 hour until the water has been absorbed, and then continue irrigating until the desired depth or amount is obtained. Best watering frequency for conservation is determined by looking for temporary darkening- bluish gray color, foot printing, wilted, folded, or curled leaves indicate that it is time to water. Proper irrigation may prevent or reduce pest problems, environmental stress and drought/heat dormancy.

Thatch Removal

Even if proper water, mowing, and fertilizing techniques are followed thatch can be a problem with KBG. Before thatching, make sure you actually have a thatch problem. Thatch is not detrimental unless it exceeds 1/2 inch. Some thatch accumulation is beneficial as it insulates the roots from heat and helps retain moisture. If needed you may vertically mow or mechanically plug aerate in late March to early May to remove the thatch (layer of un-decayed grass) BEFORE applying a pre-emergent. It is advisable to wait to address thatch until late September- early October or, if overseeding, late August- early September and incorporate de-thatching/aerating with the overseeding. Weed preasure is dramatically less in the Fall and the subsequent Spring pre-emergent will help prevent weed seed germination. Aerating is not recommended if you have rhizotomous weeds like poa trivialis or quackgrass--at the very least, those areas should be avoided.

June through August


Increase mowing height. If you will be watering regularly (2-3 times a week as needed for 1-1 1/4" of water per week) , or in the event of, extended cool and rainy periods during the Summer , height shoud be 3-3 1/2", -the heighest height at which the grass blades will stay upright and allow airflow to prevent disease/fungus.Otherwise, mow at the mower's heighest level


If you are able and willing to irrigate throughout the Summer, you can apply 1/2 pound of N/k each month throughout the Summer.Use a fertilizer with an iron content when available. Whether or not you plan to irrigate, you can use organic fertilizers like Milorganite throughout the Summer months--Milorganite has iron content which will improve the color and photosynthisis ability of the grass.. Organics will not harm turf during drought and will provide nutrients when conditions are conducive.


Follow the March through May irrigation guidelines above. If you are not irrigating regularly and allowing the grass to go dormant, you should water 1/2 to 1" every 3 weeks to keep the grass crowns alive so the turf can recover once cooler temps and rain return.

Weed Control

Apply post-emergence herbicides through-out the gowing season as needed to control Summer annual and perennial weeds such as crabgrass, clover, knotweed, and spurge. Products like WeedBgone, WBG Max with Crabrass Control and WBG CCO. Similar products with the same AI herbicides usually control several different weeds in a lawn effectively. Be sure the product is labeled for use on KBG. Use Tenacity to control Bentgrass and Poa annua.
Apply post emergence herbicides only when weeds are present. Be sure to follow label instructions and note temperature limitations of product if used.
Mid August, if you are not overseeding in the Fall, apply a pre-emergent to prevent germination of weeds like poa annua and chickweed etc if they have been present in the yard.

Insect Control

KBG grass is is most susceptable to insect damage from white grubs and billbugs and to a lesser extent to web worms. Check for these insects and control them if necessary. (e.g. Bayer 24hr grub killer)

Disease Control

Modern cultivars have increased KBG resistance to disease. Proper blending of cultivars and proper cultivation techniques (mowing, fertilization and waterng) can dramatically reduce the incidence of disease and/or disease damage, Identify any signs of disease and immediately take appropriate remedial action. If disease has been a reoccuring problem, take appropriate preventative action as and when needed.

September through November


Once the dog days of August end and night tempuratues are consistently in the 60's, incrimentally lower the mowing height to 2-2 1/2" to encourage Fall rhizome growth and spreading and to help prevent Winter snow mold.


Once Summer temperatures have moderated and the turf has revived (Late August to September 1st) apply 1# of N per 1000 sq ft. of lawn. A balanced NPK is advised such as a triple 12 or 19 to help prepare the lawn for Winter dormancy.
A second application of N (1/2-1#/k) is recommended October 1st to insure the turf stays green and photosynthesis continues.
Once the turf has ceased or dramatically stopped top-growth (mowing is no longer or barely needed), apply 1# N per thousand sq ft. (k) of urea (46-0-0) for winter root growth, carb. storage, early Spring green-up, and Spring rhizome production
In addition you can apply lime, sulfur, gypsum, etc. if a soil test indicated a deficiency.


In zones where KBG does well, Fall weather should supply sufficiant rain. Otherwise, follow the March through May irrigation guidelines..

Thatch, Aerating and Overseeding

See March - May above.

December through February

Build a snowman and enjoy the holidays.

This post was edited by grass1950 on Thu, Aug 1, 13 at 18:58

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Great information! Thanks grass1950!

    Bookmark   August 2, 2013 at 11:35AM
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