Lawn Problems

Keys for success

Maintain the right growing conditions needed for strong, healthy grasses. Healthy lawns resist moss, weeds, insects, and diseases.
Regular lawn maintenance methods include: mowing, weeding, fertilizing, overseeding, and watering. Dethatching and aerating also help.
Lawns change over time. After seed has been sown or sod laid down, a mixture of desired grasses and broadleaf weeds, grassy weeds, and moss will evolve.
Soil drainage, soil fertility, sunlight, water stress, and how the lawn is cared for and used will influence how your lawn looks over time.
Set realistic expectations for your lawn. Match the lawn standards you want to maintain with the right maintenance schedule.
If the quality of your lawn doesn’t match your standards, consider a lawn renovation.

Prevent lawn problems

See Prevent Lawn Problems to learn more about how to keep your lawn healthy. Healthy grasses in your lawn outcompete moss and weeds. They also resist damage from insect pests and plant diseases.

Moss on Roofs & Walkways

See How to Get Rid of Moss on Roofs & Walkways for more information about moss on hard surfaces.

Weeds & Moss in Lawns

Weston Miller, Oregon State University

Do you Have a Mix of Broadleaf Weeds in Your Lawn? Control for all these weeds is similar. See sections 4 and 5 for details.

Broadleaf plants have soft leaves with net-like veins.
One or more leaves grow from nodes on stems.
They often have showy flowers.
Common broadleaf weeds that grow in lawns are shown here

Joseph O'Brien, USDA Forest Service, Bugwood.org

Catsear (Hypochaeris radicata)

Catsear plants live more than two years (perennial).
It grows in lawns, landscapes, roadsides, and sidewalk cracks.
When mowed, its yellow flowers and texture stand out in lawns.
It dominates an area when left unmanaged.
Catsear benefits pollinators such as honey bees.

How to Identify Catsear / False dandelion

It grows long, slender, branching stems with yellow flowers 24-32 inches from the ground.
The leaves are less jagged and more textured than dandelion’s leaves.
Catsear forms seed head with floating seeds.

Bruce Ackley, The Ohio State University, Bugwood.org

White Clover (Trifolium repens)

White clover plants live more than two years (perennial).
It spreads aggressively by seeds and creeping stems. It forms dense patches.
When mowed, it mixes into the lawn grasses.
White clover dominates an area when left unmanaged.
These nitrogen-fixing plants grow in low nutrient soil conditions.
White clover benefits pollinators such as honey bees.

How to Identify White Clover

It grows as a dense, spreading clump.
White clover leaves have 3 crescent-shaped leaflets with a white watermark.
The white flowers attract bees.

Broadleaf Weeds in Lawns

Many species

Common broadleaf weeds (soft stems and leaves) in lawns include dandelion, clover, creeping buttercup, and many others. Minimize these weeds in your lawn by growing thick, robust grasses. Physically remove weeds as needed. Lawn-specific herbicides kill broadleaf weeds and don’t harm grasses when label instructions are followed. Follow up by reseeding areas where you have removed weeds.

Yesim Sahin, iStock

Ian_Redding, iStock

Weston Miller, Oregon State University

Grassy Weeds in Lawns

Many species

Common grassy weeds (which grow from their base and have parallel leaf veins) include crabgrass, annual bluegrass, creeping bentgrass, and quackgrass. Minimize grassy weeds in your lawn by growing a thick, robust lawn. Physically remove grassy weeds as needed. Herbicides effectively control grassy weeds when label instructions are followed. Follow up by reseeding areas where you have removed weeds.

Weston Miller, Oregon State University

mtreasure, iStock

Weston Miller, Oregon State University

Moss in Lawns

Several species in the Pacific Northwest

Moss in lawns stands out from grasses. It has a different color and texture. Scrape out moss to expose the soil and reseed grasses. Moss-killer products work to control moss in lawns. However, you still have to scrape it out and reseed. If you don’t change the conditions that favor moss, it will regrow.

Insect Pests & Diseases in Lawns

For insect pests and plant diseases in lawns, it’s helpful to determine which types of lawn grasses are growing in your lawn:

Different types of grasses that grow in lawns in the Pacific Northwest are susceptible to different insect pests and plant diseases.
See how to identify lawn grass species below.

"Leatherjacket" by Simon is licensed under CC BY-NC 2.0.

“Leatherjacket”by Simon is licensed under“CC BY-NC 2.0”.

Kansas Department of Agriculture, Bugwood.org

W.M. Hantsbarger, Bugwood.org

Insect Pests in Lawns

Many species

Learn to identify insect pests and their damage to lawns in the Pacific Northwest. Insect pests vary by the type of grass in your lawn and the climatic region (east and west of the Cascade Mountains). Growing a healthy lawn is the best way to minimize damage from insects. Find solutions for insect pests in your lawn.

"Microdochium patch" by John E Kaminski is marked with CC BY-NC-ND 2.0.

Bruce Watt, University of Maine, Bugwood.org (cropped)

Florida Division of Plant Industry , Florida Department of Agriculture and Consumer Services, Bugwood.org (cropped)

Plant Diseases in Lawns

Many species

Learn to identify plant diseases and their damage in lawns to the Pacific Northwest. Plant diseases vary by the type of grass in your lawn and climatic region (east and west of the Cascade Mountains). Growing a healthy lawn is the best way to minimize damage from plant diseases. Find solutions for plant diseases in your lawn.

Free Help Identifying Lawn Problems

Get expert pest management info and advice online from OSU's Ask Extension.

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Dog Urine Injury, Mushroom Fairy Rings & Earthworms in Lawns

fotoVoyager, iStock

Dog Urine Injury

Dog urine on lawns can burn grass leaves and form a yellow mark as shown in the photo (left). The grasses will regrow eventually. The dog urine fertilizes the grasses. If you can’t tolerate dog urine spots on your lawn, exclude dogs from your with a fence as shown in the photo (right).

"Hexenring in Freiberg" by unukorno is licensed under CC BY-SA 2.0.

A ring or semi-circle of mushrooms growing in a lawn is the most noticeable sign of a fairy ring.

"Fairy ring with jet plane" by Anders Sandberg is licensed under CC BY-NC 2.0

The fungus breaks down organic matter and produces nitrogen. This feeds the nearby grass, creating a dark green ring.

Mushroom fairy ring with green grass and bare area

"Turf fairy ring" by Scott Nelson is licensed under CC0 1.0

There may be an area of brown, dying grass inside the ring of dark green grass. Broadleaf weeds and grassy weeds may invade the damaged lawn area.

Mushroom Fairy Rings

Several species of fungi cause fairy rings

Mushroom fairy rings are caused by many species of fungi. They can grow in any type of grass. Rings of mushrooms appear in the spring or fall when the soil is moist. They feed on decaying organic matter like thatch, dead tree roots or bark mulch. This decay releases nitrogen. This causes the grass to grow dark green in a contrasting ring. Fairy rings can prevent water from penetrating to the roots of the grass, weakening or killing it. Broadleaf weeds and grassy weeds may invade the center of the ring. Fairy rings may disappear suddenly.

Joseph Berger, Bugwood.org

“Worm castings on lawn at Down House” by John Hawks is licensed under CC BY-NC 2.0 (cropped)

"Worm castings, Bwlch Mawr" by Natasha Ceridwen de Chroustchoff is licensed under CC BY-SA 2.0

Earthworms in Lawns

Lumbricus terrestris

Earthworms may disturb lawn grasses by digging under new grass seedlings. Their burrowing creates small mounds on the soil surface. Weeds may sprout and grow in bare soil.

Take Action?

Tolerate earthworms in lawns. They are a sign of healthy soil.
Rake earthworm casting piles to flatten them. Apply grass seed to fill in gaps.
There are no pesticides available for earthworm control.

How to Identify Pacific Northwest Lawn Grass Species

Perennial Ryegrass, Fine Fescues & Tall Fescue

The main types of planted grasses in the Pacific Northwest include:

Perennial ryegrass
Fine fescue (creeping, Chewings, hard, and sheep)
Tall fescue

These grass species grow as a bunchgrasses without spreading rhizomes (spreading roots) or stolons (spreading stems). Reseeding is necessary to maintain a dense stand.

Perrenial ryegrass stand with car keys for comparison

OSU Turfgrass Management Program

OSU Turfgrass Management Program

OSU Turfgrass Management Program

Perennial Ryegrass

Lolium perenne

Perennial ryegrass has a dark-green color and fine texture. The backside of leaves is shiny. Leaf blades are tapered.

Fine fescue stand with car key for comparison

OSU Turfgrass Management Program

OSU Turfgrass Management Program

Fine Fescue

Festuca spp.

Fine fescues include creeping, Chewings, Hard, and Sheep fescues. They have a gray-green to dark-green color with a very fine texture.

Tall fescue stand and key for comparison

OSU Turfgrass Management Program

OSU Turfgrass Management Program

Tall Fescue

Festuca arundinacea

Tall fescue has a dark-green color and a coarse texture.

Annual Bluegrass & Creeping Bentgrass

Also, many lawns contain grasses that grow on their own, including:

Annual bluegrass
Creeping bentgrass

Take action?

Both of these grasses stand out from lawns that contain mostly perennial ryergrass, fine fescues, and tall fescue grasses.
Determine whether you can tolerate annual bluegrass and creeping bentgrass in your lawn. They are difficult to control.
If you choose to take action for annual bluegrass and / or creeping bentgrass, see Grassy Weeds in Lawns.

Ian_Redding, iStock

OSU Turfgrass Management Program

Annual bluegrass

Poa annua

Annual bluegrass is yellow-green in color. It forms green to purple flowers (left photo) in the fall, winter, and spring. Annual bluegrass leaf tips are scooped up like the bow of a boat.

Ikbal Salehe, iStock

OSU Turfgrass Management Program

Creeping Bentgrass

Agrostis stolonifera

Creeping bentgrass is bright-green in color with a very fine texture (left photo). It is a low-growing grass with spreading stems (stolons) above the soil line.

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