Practical Lawn Establishment and Renovation

Planting a new lawn or renovating an old one can be very frustrating experience if you’ve never done it before. The key to avoiding frustration is to understand the process well enough to be able to make the right decision. This publication will take you through the steps needed to successfully plant a new lawn or renovate an old one. If you follow these steps, you will get it right the first time!

Seasonal timing

In general, the best time to plant a lawn from seed is when temperatures are favorable for rapid seed germination and grass growth. In the northern part of the United States, grass seed germination is optimum when the air temperature is between 60 and 85F. Try to time your planting so there will be 6 to 8 weeks of good growing weather after seeding.

With that in mind, the period from mid August to mid-September is almost perfect. Days are warm, nights are getting cooler, sunlight is plentiful, and day length is declining. Lawns planted during this period germinate and grow rapidly. You generally can expect to see green grass in a week, followed by the first mowing about 3 weeks after planting. By mid-October, the lawn is dense, and the soil has firmed up, so the possibility of severe rutting or footprinting is reduced.

Late-fall planting are prone to rapid encroachment by wild grasses and broadleaf weeds. If your goal is to produce a dense, clean, pure grass turf, don’t take chances on late-fall plantings. If you have no other choice, see “Tips for Beating the Calendar” for some tricks that can improve your chances of success.

There are other times when successful seeding can be done. In many parts of Oregon, the period from early May to approximately mid-June is a pretty good time to plant. Earlier plantings germinate and develop slowly, so there rarely is any advantage to planting early.

Planting later is summer causes many problems. With longer days and high temperatures, it is difficult to keep new plantings wet enough to ensure uniform germination. If you water too much, you might encourage warm-weather disease such as pythium. Once seed germinates, temperatures often are above the range for healthy root growth. The result is grass that requires constant attention all summer. Summer seedings on imported soil often suffer from excess competition from warm-season summer annual grasses, such as barnyardgrass, that arrive as seeds with the soil.

If you really must plant in summer or late fall, see the box at the left for some tips to enhance your chances for success.

What is you decide to plant sod? Sod has the same optimum planting times as seed, but because the grass is mature and has part of its root system, you can get away from planting over a much broader time period. Provided you have a well-prepared sod bed, sod can be planted anytime from about mid-March through mid-November in western Oregon. It can be planted year-round on the coast, and from about April through October in much of central and eastern Oregon, provided irrigation water is available.

Planting lawns in summer

* Don’t, if you can avoid it!

* Plant seed treated with a fungicide to prevent damping-off.

* Use the lowest seed rate in the optimum range.

* Use a light-colored mulch at a low rate or no mulch at all.

* Water very carefully to avoid drought and saturation.

* Water fertilizer in to avoid burning grass.

* Be patient and wait for fall for better growing weather.

* Hope for a cool summer!

Soil preparation

Most people think their soil is terrible. In their minds, it is either too heavy (clay) or too light (sandy). In western Oregon, most people assume their soil is too acid and infertile to grow healthy turf. East of the mountains, people believe their soil is too sandy or too alkaline to grow good turf. Many people assume they must amend their soil with organic matter or haul in new soil to provide a good root zone. It almost sounds like an impossible situation!

Although bringing in topsoil is one solution, it is not always necessary. Most native soils in Oregon have adequate fertility and pH to support turf without doing anything special. A good goal is to use the existing soil whenever possible. See the recommendations for specific regions in the box below.

Recommendations that tell you to apply lime before planting are making assumptions that are not necessarily correct. It is a safe recommendations simply because lime at the rates normally used won’t hurt (or help) anything.

Should you have a soil test done before you plant? A soil test is a good idea, but few people bother. Among other things, it takes time to get the soil test report, and then you must interpret it. It probably is wiser to spend your money in fertilizer, unless you have reason to suspect your soil is deficient in one or more elements or has a low pH.

There is more reason for concern with imported soils or when topsoil has been stripped from the site, leaving only subsoil and excavation spoils. Purchased “topsoil” might be real topsoil, river silt, clean fill from a deep pit, or someone’s idea of sandy loam. It also could be a synthesized soil made up os sand, organic matter, and soil. Most likely it is clean fill, river silt, or synthetic soil.

Clean fill usually is quite sandy and is easy to spread and grade even in rainy weather. Soil taken from deep pits might not have adequate fertility and can have a higher or lower pH than soil closer to the original surface. On the plus side, it might be relatively free of weed seed. Since it is hard to generalize about purchased soils, the only way to really know their fertility level is to have a soil test done.

If the construction process has left you with subsoil and excavation spoils, there is no way to know the soil’s fertility status. Either get a soil test or bring in new soil.

If you really can’t work with existing soils, bring in new soil that is as close as possible in texture to the original soil. This allows for continuity in water movement and rooting once the soil is in place. If you bring in sandy soil, place it over the existing soil as a layer rather than tilling it into the existing soil. A layer of sandy soil should be at least 6 inches deep, after compaction, to provide an adequate root zone. Do not till sand into clay soils in an effort to loosen up the soil or improve drainage. Research shows that adding sand reduces soil porosity and increases susceptibility to compaction until the sand content reaches approximately 80 percent by volume. Practically speaking, that means you are better off layering sandy soil on top.

Tilling organic matter into existing soil is a common recommendation. Thoroughly composted organic matter can reduce bulk density of clay soils and increase water- and nutrient-holding capacity of sandy soils. In general, you can expect a short-term improvement in tilth. Some composted materials have significant fertilizer value and will increase soil fertility for several months after incorporation.

In gardens, you can add organic matter annually to maintain the light, fluffy qualities associated with good garden soil. Organic matter added to turf soils probably is less valuable because you can add it only once. After turf is planted, the added organic matter begins to decompose further, and surface soil compaction begins. Two years after planting, it might be difficult to tell that any organic matter was added. Thus, at best, adding organic matter to turf soils has only temporary benefits.

Fresh or noncomposted organic matter can be undesirable. it generally breaks downs rapidly and in the process ties up much of the soil nitrogen that otherwise would be available for the grass. Tilling in fresh sawdust or wood chips generally results in weak, yellow grass.

Another problem with adding organic matter to soil is that if the quantity is greater than 15 percent by volume you might see considerable settlings once the organic matter decomposes. This will leave you with an uneven, bumpy lawn. Lawns where organic matter has been incorporated prior to planting also are often plagued with mushrooms.

Continued Next Week