Cool Season Grass Maintenance Guide

What is a cool season grass?

Cool season turf grass is a term applied to grass that grows well in the middle to northern half of the United States. Cool season grasses usually have two growing seasons; spring and fall. Some species go through a winter dormancy lasting between one and four months depending on location and severity of the winter. This turf tolerates cold weather very well.

See the seasonal Maintenance Guide below for maintenance tips if you have a cool season lawn.

Examples of Cool Season Grasses

Tall Fescue

Kentucky Bluegrass

Annual and Perennial Ryegrass



Spring

Winter is Over!

Spring Fertilization

Cool season grasses should be fertilized around the time that they emerge from winter dormancy and turn lush green again. Established lawns generally need only nitrogen (which is the first number on the fertilizer bag).

We recommend using a slow release fertilizer since it is both better for the environment, and will also feed your lawn for much longer than traditional fertilizer.

If crabgrass was a problem last year, you may consider putting down a crabgrass pre-emergent along with the fertilizer.

Use a fertilizer spreader to spread fertilizer. They can be obtained from any hardware or home improvement store and are relatively inexpensive. Make sure you follow the recommended rate on the bag. It is always a good idea to use a lower spreader setting than recommended and make several light passes. Selecting a spreader setting that is too high can cause too much product to be applied, which you will realize when your spreader is empty prematurely!

Get out the Mower

Mowing Recommendations

Tall Fescue and Kentucky Bluegrass will need to be mowed one to two times a week depending on growth between previous mowing. Use the following guidelines for cutting cool season grasses:

  • Ideal Mowing height: 2.5" - 3.5" inches
  • It is best to mulch clippings, which returns nutrients to the soil. Only bag clippings if they are piling up on top of the grass and cannot be removed otherwise.
  • Use a sharp mower blade, which puts less stress on the plant. This also helps to prevent fungus from damaging the grass in the summer.
  • Never remove more than 1/3 of the grass height. If your grass is too tall it should be mowed once at a high setting, and again at a lower setting a few days later.

Hold off on the hose

Watering

You will rarely find it necessary to water your lawn in the spring. Cooler temperatures and frequent rainfall will keep your soil from drying during these months.

Occasionally a spring drought may necessitate the use of irrigation, but this is rare in most of the northern part of the country.

That is the question

To overseed or to not overseed?

We recommend overseeding only if the turf requires it. Ideally, any overseeding should have been performed in the previous fall, and should now be maturing. If you did not overseed in the Fall, you should do so in the Spring. Also, if there are any dead patches or you can see the dirt in areas, it is a good idea to overseed.

Use the following guidelines:

  • Do not apply a pre-emergent herbicide. This will prevent your seed from growing, along with the weeds.
  • Overseed Tall Fescue at 3 lbs per 1000 square feet
  • Overseed Kentucky Bluegrass at 1 lb per 1000 square feet
  • You may need to water the seedlings regularly as their shallow roots are not well suited to dry soil

Summer

Less is more

Watering

Depending on conditions, you may or may not have to water your yard throughout the summer. This also depends on your expectations. If you would like to maintain a lush, perfect lawn throughout the heat of summer you are more than likely going to need to help mother nature out. However, if you can tolerate slight discoloration, both Tall Fescue and Kentucky Bluegrass can survive by turning dormant during extreme drought. Dormant grass will look yellow and "dead" but will turn green once rain returns.

It is best to water your lawn in the early hours of the day, anywhere from 4 am to 12 noon. The cooler night and morning temperatures reduce evaporative loss and reduce the amount of water needed. Additionally, following this schedule reduces the fungus pressure on your lawn by allowing the turf to dry in the afternoon. Read more about fungus below!

Not mushrooms

Fungus

The biggest concern with cool season turfgrass in the transition zone is fungal infections that strike when nighttime weather is warm (lows of 70s and above) and humid. Brown Patch in Tall Fescue and Summer Patch in Kentucky Bluegrass manifests itself as circular splotchy brown areas that slowly grow and spread. The fungus is an airborne spore that enters the plant through the tips of the blade. You can confirm a fungal infection by taking a close look at the blades. If the blade is green from the crown/base of the plant but then turns yellow and brown towards the tip, you have fungus. See more info on Brown Patch...

Luckily, following several cultural practices can prevent/ cure these summertime diseases:

  • Make sure watering is done in the morning, not the afternoon and evening. Moist grass at night sets the stage for infection!
  • Use sharp mower blades. Dull blades tear the grass, making it easier for the spores to enter the plant
  • Avoid applying fertilizer in the summer. Rapid growth actually weakens the plant temporarily and makes it more susceptible to fungus
  • Apply liquid fungicide as a preventative if the nighttime temps will be above 70 degrees. Most fungicides are inexpensive and will protect your lawn for 3-4 weeks per application

An ounce of prevention

Grub Control

Grubs can wreak havoc on any lawn, and this damage is most evident in spring and fall when the white grubs are feeding on the roots of your turf. July is usually the best time to apply chemical grub control, as this is when the beetles lay their eggs. Make sure you read the label of the the insecticide, as some must be watered into the soil after application. Grub control chemicals are not as effective in the cooler months of the year since the grubs are deeper in the soil and harder to reach with the chemical.

Fall

Do it labor day weekend

Aerate

Fall is the best time to renovate Cool Season lawns. Aeration relieves compaction and allows air to reach the roots of your lawn. It is best to use a core aerator which actually removes small cores from your lawn.

Before aerating, it is best to mow the lawn very low, which makes it easier for the machine to remove the cores. Make several passes with the aerator in different directions.

When you are finished aerating, follow the steps below for overseeding and fertilizing.

Make sure to use quality seed

Overseeding

Overseeding your lawn is best done after aerating in the fall. Overseeding will fill in any areas that may have died off during the previous year. Make sure to use quality seed that is recommended in your area. Follow this guidelines when seeding:

  • Overseed Tall Fescue at 3 lbs per 1000 square feet
  • Overseed Kentucky Bluegrass at 1 lb per 1000 square feet

You will see the seed germinate in about 7-12 days (Tall Fescue) or 14-30 days (Kentucky Bluegrass). Make sure you fertilize after seeding to ensure that the new grass has the nutrients they need to continue growing.

You lawn is hungry

Fall Fertilization

With the cooler weather here, your lawn will resume growing rapidly and need nutrients to do so. If you are overseeding, you may want to perform a soil test to see if you need to add phosphorous (the second number on the fertilizer bag). If you are not overseeding, nitrogen only (the first number on the fertilizer bag) will suffice!

Use a slow release fertilizer, as this provides a more consistent food source and is better for the environment.

Like in the Spring, make sure you follow the recommended rate on the bag. It is always a good idea to use a lower spreader setting and then go back over the area again with any extra. Selecting a spreader setting that is too high can cause to much product to be applied, which you will realize when your spreader is empty prematurely!

Rake the Leaves!

Leaf Removal

It is important to remove fallen leaves in a timely manner. A thick blanket of leaves will block required sunlight from your lawn. Don't let a layer of leaves remain on your lawn for more than a few days!

Winter

Merry Christmas

Winter Dormancy

As temperatures get colder, most cool season yards will enter a winter dormancy where they turn greenish yellow, and remain this way until spring. This is normal and is the plants' way of preserving energy.

The only thing to watch out for in the winter is an ice storm that coats the blades of grass with ice. This will not itself harm the grass but be careful not to walk on lawns covered in ice. The blades of grass encased in ice will be damage wherever you walk and you will see brown "footprints" for several months until warmer weather returns.