Lawn Care

by Rod Smith
Oregon Certified Nursery Professional

© 2001-2016 Rodney A. Smith
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A lush, green lawn really sets off a house and is usually the center of the landscape. While lawns do require weekly maintenance, it is simple and fairly easy. Lawn maintenance can be even easier if some thought and effort is put into establishing the lawn.

Choosing a grass

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. The best choices for the northern half of the US are cool season grasses, which grow the most in the spring and fall. 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 wonít 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.

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 a conventional lawn is an Eco-Lawn. Most Eco-lawns are a mixture of grasses, clovers, and flowering plants, such as, English Daisies, Roman Chamomile, Sweet Alyssum and Yarrow. Eco-Lawn seed mixes are available locally from Pro Time Lawn Seed. They will stay green all summer with only 1.5 inches of water once a month. They can be mowed three to five inches high every three weeks, or left un-mowed. However, they are not the same as a mowed lawn, and many people rip them out after a few years and plant conventional lawns.

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 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.

Establishing a lawn

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 35 cents per square foot and grass seed costs about 3 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 an inch high.
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, just enough to keep the soil moist.

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 first two steps are the same, but 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.

For seed, spread the seed and rake it in lightly with a leaf rake. Then cover the seed with peat moss, compost or grass clippings. Keep the soil moist for three weeks.

For sod, if the weather is sunny and hot, spray the soil with water to make it cool and moist before laying sod on it. Lay sod beginning with the longest straight line. Walk on the sod, not the soil, to avoid leaving depressions in the soil. Roll out the sod in the same directions so the beveled ends overlap. Pull the sides of the sod tight together and stagger the cross seams. When the sod is all laid and the edges trimmed, empty half of the water out of the water roller and go over the sod diagonally so the sod is tight to the soil. Keep the sod constantly moist for two weeks until the sod is rooted into the soil.

Mowing

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. If the wheel tracks are still visible from the last mowing, then 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. For riding mowers, I mow a different width on the second round, either one-third, two-thirds or full width. This varies the wheel tracks for the rest of the yard.

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 3.5 inches will reduce water and fertilizer needs. Mowing at 1.5-2 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 is 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. If the lawn gets too tall, set the mowing height higher, then, a few days later, mow the lawn again at the regular height. This is especially important during hot weather.

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

Edging the lawn along sidewalks and driveways is optional but it gives the lawn a professionally manicured look. A straight, sharp edge looks professional but a 3-inch wide trench looks amateurish. An electric or gasoline powered edger will cost about $100. String trimmers also can be used for edging, but they require more skill. Hand edgers can be purchased for about $20.

Watering

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 doesnít run off. The best time to water is right after sunrise when the air is cool so less water evaporates before it hits the ground.

Fertilizing

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. One containing blood meal as the nitrogen source is the best choice.

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 by the right amount.

Insect Control

Lawns in the Northwest are occasionally attacked by chinch bugs and grubs but the most damage is done by crane flies and billbugs. This summer brought the worst lawn damage I have ever seen, because two new insects have moved into the Portland area: common crane fly and billbug.

The common crane fly resembles the European crane fly, which has been in the area since the 1980ís. Both look like giant mosquitoes and both have larvae that feed on grass roots. Damaged grass can be pulled right out of the ground because there are no roots. The difference is that the common crane fly has two generations each year. European crane fly larvae stop feeding in June, but the second generation of common crane fly larvae feed in July and August when lawns are the most stressed. Lawns can tolerate up to thirty European crane fly larvae per square foot without causing any visible damage, but I saw lawn damage with only twelve to fifteen common crane fly larvae per square foot in August.

The surest way to tell if common crane flies are present is to watch for the adults. Both kinds of adult crane flies are present in late summer, but only common crane fly adults are present in the spring. Keeping the soil on the dry side in the fall reduces the survival rate of crane fly larva. So, cut watering way back, or stop completely if possible, after Labor Day.

Billbugs are not as widespread as crane fly, but a few will cause considerable damage. One or two larvae per square foot are enough to kill the grass. Billbugs have been a problem in northeast Oregon for years, but they were first found in Tualatin in 2012. In 2013, I found them, or heard reports of them, in Wilsonville, Newberg, Hillsboro, Beaverton, and northeast Portland. Young larvae feed inside grass roots. Older larvae feed on the crowns of grass. The grass turns brown and collapses so it lies flatter to the ground. Grass can be peeled off to reveal bare soil. Sometimes, larvae are visible on the surface of the bare soil, but they are usually a half inch deep in the soil. The oldest larvae are a 3/8 inch long white grub with a brown head. Adults are a weevil with a long, round snout.

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. A quicker way is to pull apart the plug of lawn and look for insects. Almost all lawn insects, except billbugs, can successfully 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. Bifenthrin, cyfluthrin and imidicloprid are effective chemical controls for most lawn insects, including billbugs.

Disease Control

The three most common lawn diseases in the Northwest are Leaf Spot, Rust and Red Thread. Leaf Spot produces purplish spots with straw-colored centers on the grass blades. Rust is orange powder on the blades. Red Thread has tiny red filaments that grow across the lawn. Cultural controls include: regular, balanced fertilizing and watering to keep the grass growing strong, although excessive fertilizer in the fall and winter promote leaf spot; a mowing height of 1.5-2 inches, which cuts off the diseased spots before they become noticeable; Red Thread can be spread by the mower, so mow diseased areas last, then thoroughly clean the mower. If cultural controls are not sufficient, then Daconil, Eagle, Heritage, Mancozeb or Spotrete F fungicides will control all three diseases.

Weed Control

Weeds are either broadleaf, such as dandelions and clover, or grassy, such as crabgrass and annual bluegrass. A complete list of common lawn weeds with pictures and a key to identify them is at http://www.ipm.ucdavis.edu/TOOLS/TURF/PESTS/weedkey.html. Broadleaf weeds are easiest to control since many lawn weed killers will kill broadleaf weeds without harming grass. The active ingredients in most broadleaf weed killers are 2,4-D and Dicamba. 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. Quinclorac is effective at killing crabgrass, clover and dandelions, and is safe to use on ryegrass and most fescues, but not all 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 a few days after mowing.

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, but 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 winter before moss smothers the grass. Almost all moss killers for lawns contain iron sulfate. It will stain concrete so sidewalks, driveways and patios should be blown or hosed off immediately after moss killer is applied.

Aerating

Soils that get walked on or trampled will pack down until air cannot penetrate into the soil to keep the roots healthy. If a lawn has patches where grass will not 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.

Thatching

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 and may be beneficial. 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 an inch tall 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.

Choosing the right grass is the most important step in keeping a lawn attractive with minimum labor and expense.


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