Lawn Care

A beautiful lawn begins with choosing a type of grass that is suitable for the climate. Many types and varieties of grasses are now available. For the western valleys of the Pacific Northwest, the best choice is perennial ryegrass for full sun and a mixture of perennial ryegrass and fescue for part-shade. New varieties of these grasses have a fine texture and good green color. One drawback to perennial ryegrass is that it has to be watered enough to keep it green during the growing season. Otherwise, it thins out until the lawn is dense clumps with bare spots in between. Perennial ryegrass will not spread to fill in the bare spots like most other grasses so bare spots need to be reseeded. A lawn that won’t be watered should be at least half fescue. Fescue is much more drought tolerant and will come back quickly when rainfall resumes.

Kentucky bluegrass is better for the area from the Cascades to New England and the higher elevations of the upper South. Buffalo grass is not as nice looking but it is requires much less water. Bent grass was very popular thirty years ago but it takes much more water and fertilizer to keep it green. Also, it is susceptible to every known lawn disease.

These are cool season grasses that grow the most in the spring and fall. For the South, warm season grasses are used such as Bermuda grass, Zoysiagrass, centipede grass and St. Augustine grass. Each has it strengths and weaknesses. Since they go dormant in the winter, annual ryegrass is often over seeded in the fall so the lawn will stay green all winter.

An alternative to grass is dwarf pennyroyal, which is a low growing mint. I used it in a small courtyard and it worked very well. It only needed mowing once a month and smelled wonderful. Also, it discourages fleas. However, it does not hold up to heavy foot traffic so I had to put stepping stones in the path I walked every day. I have also heard of a lawn of wild garlic in arid central Oregon, which stays green all year without any watering.

New lawns can be planted by seed or sod. For seed, the soil must be at least 55 degrees for the seed to germinate quickly. This is from mid-April to mid-October in western Oregon. Sod can be laid from March to November. Preparation is exactly the same. The biggest difference is cost. Sod costs around 25 cents per square foot and grass seed costs about 2 cents. However, sod is better if the ground slopes enough to cause erosion.

If a lawn has good soil but weedy grass, it can be renovated and replanted without tilling the soil. The steps are:
Spray the old grass with Roundup, and wait seven days.
Mow the grass as short as possible.
Use a thatcher, also called a power rake, to loosen the old grass and soil, then rake off the old grass.
Spread grass seed fertilizer and also lime if needed.
Spread grass seed evenly over the area.
Rake it in with a spring tooth rake or leaf rake.
Spread a thin layer of mulch over bare patches.
Water every day for three weeks.

If sod will be laid or the soil is poor or has high and low spots or needs to be re-graded, then it is better to till the soil and re-grade. See the article on Improving Soil for more information on poor soil. The steps are similar. Instead of using a dethatcher, spread lime and soil amendments, then rototill or spade as deep as possible, level the soil and roll it with a water filled roller and level again. Then continue with the grass seed fertilizer. Spread seed or lay sod beginning with the longest straight line. Walk on the sod, not the soil to avoid leaving depressions in the soil. Pull the sod tight together and stagger the cross seams. Then empty half of the water out of the water roller and go over the sod diagonally so the sod is tight to the soil.

A new lawn should be mowed as soon as it reaches regular mowing height. The mower should be sharp because a dull blade might rip young seedlings out of the soil. Then regular mowing, usually weekly, during the growing season is the main task in maintaining a lawn. It is a good idea to vary the mowing pattern. I mow a clockwise spiral one week, then north-south the next week, then a counterclockwise spiral, then east-west. This prevents ruts from running the mower wheels in the same track each time.

Mowing height is measured from the mower blade to the ground with the mower sitting on a flat surface. Mowing height for most grasses is 1.5 to 2 inches. For the summer, a mowing height of 2.5 to 3 inches will reduce water and fertilizer needs. Mowing at 1.5 inches during the rainy season reduces disease problems. Grass should be mowed as soon as it reaches one and a half times mowing height so only one third of the grass height it mowed off. If grass is allowed to get tall, then cut short, the soft, lush base of the grass will be exposed to hot sun and it will burn and turn brown. For tall grass, set the mowing height higher, then, a few days later, mow the lawn again at the regular height.

I recommend buying a mower that can either mulch or bag the clippings. Mulching the clippings back into the lawn builds up the soil and requires less fertilizer, but if the grass is tall or wet, the clippings may pile up and smother the grass. The grass clippings should be bagged if they start to pile up. Also, it is better to bag the clippings if kids or guests will be tracking grass clippings into the house.

Edging the lawn along sidewalks and driveways is optional but it gives the lawn a professionally manicured look. An electric or gasoline powered edger will cost about $100. Hand edgers can be purchased for about $20, but the half moon edger is not nearly as easy to use as the Lawn Shark edger which has a triangular blade with teeth on the long edge to cut through grass. A straight, sharp edge looks professional but a 3-inch wide trench looks amateurish.

Most grasses in most of the country need the equivalent of an inch of rainfall each week. More is needed during hot weather or in arid climates. If the grass has a dull appearance or it fails to stand back up after being stepped on, it is dry and needs watering immediately.

Clay or sandy soils usually need a half-inch of water two or three times a week. If the soil is loose and has lots of organic matter to hold water, an inch could be applied once a week. Watering every day prevents the grass from growing a deep root system and also causes tree roots to grow on the surface of the soil.

A handy way to measure how much water is applied is to scatter some tuna or pet food cans in different parts of the lawn. Whether hose end sprinklers or underground sprinklers are used, water should be applied evenly and slow enough that it soaks in and doesn’t run off. The best time to water is right after sunrise when it is cool so less water evaporates before it hits the ground.

Fertilizing a lawn regularly will give it healthy green color as well as help prevent disease and weed problems. If a lawn is well fed and growing rapidly, disease spots on the grass blades are mowed off before they become visible. A thick lawn will prevent weeds from getting started.

Lawns need mainly nitrogen, phosphorus and potassium or NPK. The numbers on every fertilizer bag are the percentages of N P and K found in the bag. Different lawn grasses need different amounts of nitrogen with bent grass and Improved Bermudagrass needing the most and fescue and centipede grass needing the least. A general recommendation that will do well with most grasses is 0.75 pounds of actual nitrogen per 1000 square feet every 6 weeks during the growing season. Divide 0.75 by the decimal form of the percentage of nitrogen to find how many pounds of fertilizer to apply each time. For example, a 15-5-10 would require 0.75 / 0.15 which equals 5 pounds of fertilizer per 1000 square feet every six weeks. A different approach for cool season grasses is to fertilize once in early spring and again in late summer. In that case, divide 1.50 by the decimal form of the percentage of nitrogen. This approach requires a slow release, non-burning fertilizer such as one containing blood meal as the nitrogen source.

Regarding which fertilizer to use, a turf research project at Oregon State University comparing many different lawn fertilizers and ingredients determined that every one tested worked equally well after one month. The only difference was that blood meal was still working after three months.

Fertilizer spreaders can be as simple as a hand crank Whirlybird for $12 or a wheel-driven spreader for $60. Wheel-driven drop spreaders are the most accurate but the wheel tracks have to be overlapped just the right amount to avoid gaps or double applications. Wheel-driven broadcast spreaders usually give the best results. The fertilizer tapers off at the edges so there is not a sharp line if the spreader is not overlapped enough.

Lawns in the Northwest are occasionally attacked by chinch bugs, bill bugs, and grubs but the most common insect is the European cranefly which looks like a giant mosquito. Cranefly eggs hatch into larvae in the fall. The larvae feed on grass roots from September through May then the larvae pupates and emerge as adults in late summer. There can be as many as thirteen larvae per square foot without causing any visible damage. Greater numbers cause dead patches of grass, which can be pulled right out of the ground because there are no roots. The easiest way to check for soil insects is to dig up a plug of lawn on the edge of a dead spot, put it in a plastic bag and see what crawls out of the soil. Almost all lawn insects can be controlled by applying beneficial nematodes which are microscopic worms which prey on many soil insects. Beneficial nematodes are effective at killing soil insects without affecting earthworms or mammals.

Weeds are either broadleaf, such as dandelions and chickweed, or grassy, such as crabgrass and annual bluegrass. Broadleaf weeds are easiest to control since many lawn weed killers will kill broadleaf weeds without harming grass. The active ingredient in most broadleaf weed killers is either 2,4-D or Trimec. Weed and feed fertilizers have to be applied evenly over the entire lawn even where there are no weeds. I prefer to use a plain fertilizer, then spot apply liquid weed killer only on the weeds.

Grassy weeds are harder to control since most grass killers will kill lawn grasses as well as weedy grasses. A grassy weed preventer, such as Halts or Team, can be applied in the spring when the first dandelion blooms to prevent crabgrass and around Labor Day to prevent annual bluegrass. Coarse grasses which grow taller than the lawn grasses can be controlled by using a paint brush to apply Roundup to the taller tips.

The best weed control is a thick healthy lawn that crowds out weeds. Weeds are a sign that the lawn is stressed, usually by poor soil, lack of regular watering, lack of fertilizer or mowing too short. I once visited a natural prairie area on the edge of a school yard. The school yard was so full of dandelions that they overlapped but there were no more than a handful of dandelions in the entire prairie. The dandelions ended right at the edge of the mowed area. Low mowing allows more sunlight to reach the soil which encourages weed seed growth while a higher mowing height causes the soil to be in deeper shade, which discourages weed seed growth.

Another common weed is moss. It is almost guaranteed to grow during the rainy season anywhere there is shade. By spring, moss will have killed out quite a bit of grass. It is better to use moss killer in early winter before moss smothers the grass.

Almost all moss killers for lawns contain iron sulphate. It will stain concrete so sidewalks, driveways and patios should be hosed off immediately after moss killer is applied.

Soils that get walked on or trampled will pack down until air can’t penetrate into the soil to keep the roots healthy. If a lawn has patches where grass won’t grow in spite of fertilizing and watering, it needs to be aerated. An aerator punches holes in the lawn ever few inches to allow air and water to penetrate into the soil faster and deeper. The easiest and best way to deal with the cores that are left on the surface is to mow over them and scatter the soil onto the lawn surface. This fresh soil brings up microbes which help break down thatch.

The frequency of aerating depends on the soil and the amount of traffic on the lawn. Athletic fields are aerated every few months. A yard on clay soil with active kids may need aerating every year. On the other hand, a yard with rich soil and lots of earthworms may never need aerating.

Thatch is a layer of dead stems and roots that can build up on the surface of the soil. If you dig into the lawn with your finger, it is fairly easy to tell the difference between the soft, light thatch and the hard, heavy soil. A quarter inch thick layer of thatch is of no concern. If thatch is an inch thick, disease problems are almost sure to occur. Also, a thick layer of thatch will make a lawn require more water and fertilizer to keep the lawn green.

There are several products available to reduce thatch. They contain microbes that will break down thatch quicker. If the thatch is an inch thick, then it is better to use a thatcher, also called a power rake, to quickly remove thatch before diseases develop. Before using a thatcher, mow the grass as low as possible to reduce the damage to the grass. Set the depth on the thatcher so the teeth just reach the mineral soil. Then run the thatcher over the lawn twice, going east-west one time and north-south the other. The loosened thatch then needs to be raked up and hauled away. Do not bother adding it to the compost pile since it is tough roots and stems which are very slow to break down.

Thatching usually leaves bare patches so it is a good idea to spread starter fertilizer and grass seed after thatching so the bare patches fill in before weeds get started. Therefore, thatching should be done from mid-April to mid-October.

The frequency of thatching depends on the type of grass. Bentgrass, Kentucky bluegrass and creeping fescue may need to be thatched every year or two. Perennial ryegrass and tall fescue may never need to be thatched.

More information can be found on my webpages:
Landscape Design | Improving Soil | Plant Nutrients | Planting in Clay Soil | Roses
Edible Landscaping | Fruit Tree Tips | Planting a Vegetable Garden | Lawn Care | Pest Control
Pruning for Shade, Flowers and Fruit | Seasonal Pruning Guide | Remove Trees Roots and All
Fall Planting | Water Wise Gardening | Winter Plant Protection | Oregon Invasive Plants
Oregon Native Landscape Plants | House Plants | Plant Propagation

Lawn Care Guide to lawn care, grasses and mowers.
The Grass Guide Lawn Management Information.

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