Bluegrass Seed Heads

How to Care for Kentucky Bluegrass

Do you struggle to keep the Kentucky bluegrass in your lawn green in the summer months? Are you seeing what looks like lighter-colored, delicate little weeds growing in your lawn? If you answered yes to either of these questions, this post will help you learn more about your lawn and how to take care of it.

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Basic Structure and Care of Kentucky Bluegrassbluegrass anatomy chart

Grass plants are made up of the primary stem/blade, the tiller blades, the crown, the rhizome/stolon, and the root system. The tiller blades are the new blades that grow from the primary stem to replenish the older grass blades. The crown of the grass is right at the base of the plant. This is where all new grass blades and roots grow from. The rhizome and stolon are roots that extend horizontally from the crown of the grass to create new growth.

Like many other grasses, Kentucky bluegrass is a cool-season grass, so it prefers mild temperatures and generally thrives in cooler climates. For this reason, it often grows well in Utah’s spring and fall months, but struggles during hot, dry Utah summers.

To help combat this problem, you can plant a tough, disease-resistant ryegrass seed mixture along with your Kentucky bluegrass seed. This will help your grass stay healthy even during hot summer months.

Here are a few other ways you can ensure the survival of your grass during the summer:

  • Water the correct way!
  • Fertilize periodically throughout the year—especially in the fall.
  • Keep your lawn 2–3 inches long in the summer.
  • Aerate yearly and overseed when needed.
  • Pull up persistent weeds in the fall and reseed those areas.

Water the correct waymeasuring water in the lawn

In the summer, Kentucky bluegrass lawns need 2.5–3 inches of water a week. To determine how many inches of water your lawn is currently receiving from your sprinklers, try following these steps:

  1. Place clear containers on the lawn at regular intervals and run your sprinklers as normal.
  2. Use a ruler to measure the height of the water in each container.
  3. Multiply this number by the number of times you water each week to find the amount of water your lawn is currently getting each week.

To determine the most effective watering schedule for your lawn, keep the following in mind:

lawn sprinkler close-up

  1. Water less often for longer periods of time (watering 3 times a week for 30 minutes each time is generally better than 6 times a week for 15 minutes). Doing this will strengthen your lawn’s root system, which will keep your lawn healthy.
  2. Give special attention to dry spots. When checking how many inches of water your lawn is getting, place containers on dry spots specifically to see if the sprinklers are missing those spots. Then adjust your sprinklers as needed or water those areas by hand.

In the spring and fall, your lawn needs less water—about 1.5–2 inches a week, so adjust your sprinkler time accordingly.

Fertilize periodically throughout the year—especially in the fall

Fertilizing in the spring will help wake up your lawn, and fertilizing in the summer will help keep it green while it’s under the most stress.

Your lawn also needs fertilizer in the fall to prepare it for the next couple of seasons. Kentucky bluegrass will take in the fall fertilizer and use it to strengthen its roots. Developing a strong root zone this way will help it survive the harsh summer months, so fall is arguably the most important time to fertilize.

Most lawns do best with about 6 fertilizer treatments a year, spaced about 4 to 6 weeks apart. Start your first fertilization treatment in early to mid-spring and apply your last treatment of the year in mid-to-late fall, before it snows.

Keep your lawn 2–3 inches long in the summerlawn mower

If you keep your lawn longer in the summer, it will allow the bottom half of the grass to stay cooler, delaying the effects of drought stress. This is just one of the many benefits of keeping your grass longer in the summer. Longer lawns also help prevent grubs from laying their eggs near the soil where they can feed on the crowns and roots of the grass.

Keep your lawn long in the summer because long lawns do better than short lawns during the growing season, but in the late fall cut your lawn short for the winter months. Cutting the lawn short for the winter will help prevent it from becoming matted down, which will help prevent snow mold from growing.

Pull up persistent weeds in the fall and reseed those areas

Some weeds return every year and can’t be killed with regular lawn weed control sprays. Fall is a good time to pull them up and reseed where they once were. Doing this will allow your lawn to grow back thicker in those areas, hopefully choking out any weeds that try to grow back.

Additionally, you can prevent weeds from growing in the summer by applying a weed preventative spray (pre-emergent) to your lawn in early spring.

Kentucky Bluegrass Lifecycle

Kentucky bluegrass is a perennial grass, which means it grows from the same plant each year and simply goes dormant in the winter months. Anytime the temperature goes higher or lower than the sweet spot for this type of grass (50-75° F), it begins to go dormant. This is why it often struggles to stay active (and green) during Utah summers—and not just during the winter months.

The root system of the grass usually replaces itself about twice a year. Individual grass blades die off after about 40 days, but new blades (called tillers) are constantly growing. If the new blades grow and replenish faster than the old ones, the lawn will be thick and healthy.

Though Kentucky bluegrass will continue to grow from the same plant each year, in the spring it will also attempt to regenerate by sprouting little seed heads that are often mistaken for weeds.

Bluegrass Seed Heads: Not Actually a Weed

Bluegrass Seed Heads
Bluegrass Seed Heads

The thin, light green weeds growing in the bluegrass pictured here are actually not weeds at all. They’re bluegrass seed heads.

Seed heads will sprout in healthy lawns each spring as part of the natural growth cycle—this is the lawn’s attempt to reseed itself. However, it takes months for the seed heads to grow and dry out enough to re-seed the lawn, and most varieties of store-bought seed are sterile anyway.

Keep in mind that if the seed heads are left to grow, they may weaken the grass because nutrients will be allotted to the new growth rather than to strengthening the root system. Though the seed heads won’t do much to thicken your lawn, they are harmless and can easily be mowed down. Additionally, seed heads can be beneficial to the roots of the lawn when they’re mulched during mowing.


Aeration is helpful for lawns—especially lawns that have compacted soil and problems with necrotic ring fungus. Aeration opens up the soil, allowing vital nutrients and water to reach the root zone more effectively.

Many lawn experts recommend aerating once a year, but some lawns can go two or three years between aerations and still be healthy. The general rule is to aerate when the thatch layer is thicker than half an inch. When the thatch layer is thicker than this, it can prevent the lawn from intaking vital nutrients and can cause the lawn to thin out.

Diagnosing Lawn Issues

If you have yellow spots in your yard, you can diagnose what the problem is by trying these tests:

  1. Pull up on the yellow grass blades.
  2. Stick a screwdriver or soil probe into the yellow areas and note how easily it passes through the soil.
  3. Examine individual grass blades and check how much of the blade is yellowing.

Pull up on grass blades

bluegrass grub damage
Grub Damage

If the lawn pulls up as a carpet would, then the grass blades have been separated from the roots, which indicates a grub problem. Some types of grubs start eating grassroots in the spring, but more serious grub damage occurs in the summer and fall. Try to eliminate the grubs as soon as you recognize the signs because grubs can quickly destroy your lawn.

If individual blades of grass come loose when you pull on the grass blades, this can indicate that drought stress or a fungus is the problem. Drought stress will cause the grass blades to look grayish-blue before they turn yellow and brown. Lawn fungi, on the other hand, tend to create patterns in the grass. For example, necrotic ring fungus creates yellow circles in the grass.

Screwdriver test

If the soil is healthy, the screwdriver should pass through it easily. If it stops short or if it’s too difficult to push the screwdriver into the soil, then the soil is too dry and compacted. Grassroots have a very hard time growing through compact soil, but aeration can help break up compacted soil, and proper watering can help moisten it.

Check individual grass blades

grass blade with ascochyta

Closely examine a few of the grass blades to see how much of the grass is damaged. If just the top half of the blade is yellow, it’s probably a fungus called ascochyta. If the entire blade is yellow, it could either be fertilizer burn or drought damage.

Common Lawn Diseases

Two common fungal diseases that affect Kentucky bluegrass lawns in Utah are necrotic ring and ascochyta.

Ascochyta lives in the thatch layer of the lawn and usually flares up after fluctuations in temperature and moisture. Overwatering followed by warm, dry weather are perfect conditions for ascochyta. Ascochyta causes the lawn to turn yellow temporarily—it usually dissipates within a few weeks with proper care. Though there is no real cure for ascochyta, you can decrease the chance of spreading the fungus every year by aerating to help reduce the thatch layer (which is where this fungus lives).

necrotic ring spot
Necrotic Ring Spot

Necrotic ring fungus creates yellow rings in the lawn and thrives in wet conditions. Because the fungus lives in the soil, it cannot be removed. Necrotic ring dissipates over time (usually 3–5 years) with proper lawn care. To care for your lawn properly, you’ll need to aerate your lawn at least once a year, if not twice. Aerating will help open up the soil, allowing it to breathe and dry out. This is important for necrotic-ring-infested grass because the fungus needs plenty of moisture in order to survive.

You should also make sure you’re watering correctly and using a special type of fertilizer for ring spots to give the lawn a boost. You can also over-seed affected areas with disease-resistant ryegrass to help combat necrotic ring.


Need help caring for your Kentucky bluegrass lawn this year? Call or text Stewart’s lawn experts at 801-226-2261 for a free quote and more information today!