Buying and Installing Certified Sod

Revision Date: 10/1/1995
Susan Barton, Ornamental Horticultural
Specialist III

A beautiful lawn provides the perfect background for a home. It can be functional as well as attractive, and if well cared for, it will last for decades. The initial cost can be spread over many years so the annual expense is surprisingly low. New production and harvesting practices have made it possible for commercial sod growers to supply lawn and garden centers with high- quality sod while at the same time holding the line on prices. This is reflected in the attractive offers that are now being made by retail suppliers.

Like a house built on sand, your beautiful sod can be destroyed in hours by improper care at the outset. Its roots have been severed in the harvesting process and this makes it totally dependent on your tender, loving care for at least the first three weeks of its new life.

Before making an investment in sod, there are a number of things to consider. The most important is: How do you know you are buying good-quality sod? Once purchased, how should it be cared for, especially during those first critical days? These and other questions will be covered in the following paragraphs.

What is cultivated-certified sod? Grass which is grown by turfgrass specialists for the purpose of lifting as Turfgrass sod is referred to as cultivated sod. In Delaware, it usually takes about 18 months, to produce high-quality turfgrass sod that is ready for lifting. Certified sod can be only cultivated sod that is produced from certified grass seed. The seed must be examined and tested before it can be planted. Even the soil itself must be examined prior to planting to make certain it contains no noxious weeds or harmful pests. The sod must be inspected prior to harvest to check on off-type grasses, weeds, insects, and diseases. If problems are found, they must be corrected before sale as certified sod is permitted.

Why is cultivated-certified sod the best buy? Certified sod is marked with a blue tag, which signifies that it was grown from certified seed of adapted turfgrasses and that the sod fields have been inspected and found to meet published standards for certified sod. The certification tag or sticker on the invoice is the best assurance you can have that the sod being purchased is of known variety or varieties and is essentially pest-free.

Who is responsible for certification of sod in Delaware? Certification in Delaware is a joint responsibility of the Delaware Crop Improvement Association,. a non-profit Delaware organization designated the official certifying agency by the Delaware Department of Agriculture, and the College of .Agricultural Sciences at the University of Delaware.

What is meant by pasture sod? Sod is sometimes lifted from pastures, hay fields, abandoned cemeteries and areas soon to be used for construction. Sometimes this so-called pasture sod will satisfy a need. More often it introduces a new set of problems. The grasses are usually a mixture of unimproved strains. Weeds such as nutsedge and garlic are often present in a dormant state and will surprise you a few months later when conditions are favorable for their growth.

Isn't sodding more expensive than lawn seeding? Given optimum conditions for both seeding and sodding, it is less costly to seed. If conditions don't favor seeding, then reseeding costs, poor stands and other less tangible losses can make sod the best buy when the following conditions exist: on sloping land where erosion is a problem, when lawns must be established at times unfavorable for seeding and where an attractive, functional lawn is needed right away. There is no good substitute for sod.

How should the soil be prepared for sodding? The soil should be prepared as it would be for a grass seeding. It is not necessary to cultivate or work the soil deeply, but all vegetation should be killed and the sod piece placed in contact with base soil. If mushroom soil is added prior to sodding mix it with the underlying soil to a depth of 2 inches to avoid distinct layering. Textural layers tend to obstruct the normal development of roots.

Are lime and fertilizer necessary for sodding? Yes! A light application of lime and fertilizer will often make the difference between success and failure in sodding. The cost of materials is small in relation to the total cost of sodding. Apply 10-15 pounds. of a complete fertilizer, such as 10-10-10, per 1,000 square feet of lawn. Follow this with 50-75 pounds. of ground limestone per 1,000 square feet. Mix these with 1-2 inches of soil when preparing the area for sodding. Certified sod is grown on well-limed and fertilized soil, but don't be tempted to skip this additional application as part of the sodding operation.

When during the year can sod be installed in Delaware? Anytime that it can be harvested at the sod farm. Of course it can't be harvested when the ground is frozen, but sometimes in Delaware it can be harvested and installed during every month of the year. Sod that is harvested during the winter months will be less attractive because of the discoloration which occurs during winter dormancy. Sod installed during cold weather, however, requires less care than sod installed during hot summer months.

What is the best thickness for sod? No single cutting depth is "best." This will vary depending on age and type of sod. First priority must be given to sod strength. The sod piece must hold together when it is being handled, shipped and installed. Sometimes a slightly thicker sod will increase the sod strength. As a general rule, the thinner the sod piece, the faster it will root into or bond with the underlying soil. A 3/4" sod depth is perhaps the most frequently used. This is usually composed of about 1/4 inches of soil and l/2 inches of grass roots, thatch, etc.









Is it necessary to roll the sod after installation? It's important to establish good contact between the new sod piece and the underlying soil If the soil is not smooth and well-prepared, rolling can serve to achieve the soil contact that is essential for rapid knitting. On a well prepared soil, this can be accomplished by generous use of water.









How important is watering? Watering is so important that you shouldn't purchase sod until you have your watering or irrigation system in place and ready to operate. Sod can be frozen and mishandled in many ways without serious damage. But if sod heats in a roll or on a pallet or dries out before or after installation, it will die. There should be a clear understanding between the supplier and buyer on the subject of watering. The higher the temperature, the greater the need for water. In some cases it is advisable to wet the soil thoroughly prior to installing sod. This should be done a few hours before installation of the sod so the soil will be firm and not difficult to walk on. Sod will normally knit with the underlying soil in about two weeks but it will take a month before the roots have extended deep enough for the grass to survive any extended period without water. You can survive some mistakes in sod handling, installation and growing, but if sod heats up before installation or drys out after it will die.

Do weed, insect and disease problems ever occur in certified sod? Yes! Weed seeds can lie dormant in the soil for many years. When favorable conditions develop such as high acidity, low fertility, excessive moisture, compaction or light intensity at the soil surface, seeds can germinate. Most soils contain many kinds of dormant weed seeds. The same can be said of insects and disease organisms. Sod producers try to maintain an environment that prevents the development of these pests. Sometimes they resorts to the use of pesticides to achieve this. In many cases the certified sod you purchase has already been treated for crabgrass control for the year of purchase.

What grass varieties or mixtures are best for sod? The same grasses which make a good seeded lawn will of course be best for a sodded lawn. Certified sod in Delaware will contain two or three varieties of Kentucky bluegrass plus a small amount of red fescue. These are available as 40-40-20 or 30-30-30-10 mixtures based on the percent of each grass in the seed mixture expressed in a weight basis. The Kentucky. bluegrasses are chosen to compliment each other. The red fescue, at 10-20 percent of the seeding mixture, is sufficient to satisfy shade requirements of a maturing landscape. Tall fescue - -Kentucky. bluegrass mixtures (80- 20 or 90-10) are available for use in activity or heavy-wear areas. This is also a relatively drought tolerant mixture which does well on sandy soils.

Things to look for when buying sod: Buying is simplified when dealing with certified sod. Public agencies have already established the genetic purity of the grass and its relative freedom from weeds, insects and diseases. At point of sale it must meet additional minimum standards for density, color and general appearance established by the Delaware Crop Improvement Association. If these standards are not met by the grower or retailer, the certification tag or seal is removed from the sod.






You should examine all types of sod, however, for weeds, off-type grasses, diseased areas and presence of damaging insects. Ask if the sod has been treated with pesticide for insect control or with a systemic fungicide for disease control. If the sod has heated in a roll or on a pallet and has a greenish-yellow appearance, don't accept it. Sod that is very dry and has a bluish-green cast should be examined critically. This is especially true if the temperature is high. It may have suffered a moisture stress that even good watering will not overcome. Don't buy it! A 3-4 foot strip of sod should hold together when suspended. If it doesn't it will be difficult to handle when installed. Sod grown on uneven soil will often have holes and when installed, their openings invite weed growth from the exposed underlying soil. Reject those pieces and ask that they be replaced with good sod.

If problems develop after the sod is in-stalled and established, who is responsible? The buyer. Garlic and nutsedge can germinate at depths of 4 to 5 inch and emerge through your new sod. If the sod is dense and healthy, this will not usually happen for at least a year or two after installation. However, it is possible and it is in no way the responsibility of the supplier. Weed seeds are constantly moving from lawn to lawn as are lawn insects. There is a certain level of disease organisms in every lawn. It is only when the balance is upset that the combined stresses overcome the grass and easily visible disease symptoms appear. This can happen anywhere, anytime, and is not the responsibility of the supplier.

Is a written agreement necessary when buying sod? No. To avoid misunderstandings, however, it is well to negotiate some kind of a written agreement. This is especially important if a large area is being installed by the supplier. The agreement should cover items such as:

  • Quantity, type of sod and price per unit or job.
  • Time, place or manner concerning acceptance or rejection of sod.
  • Preparation of land and application of lime and fertilizer.
  • Application of water prior to and following installation.
  • Settlement date at which time all responsibility reverts to buyer.


Original author: W.H. Mitchell

Original Publication Date:

Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State University and the United States Department of Agriculture cooperating. Distributed in furtherance of Acts of Congress of May 8 and June 30, 1914. It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, color, sex, disability, age, or national origin.

Disclaimer: Reference to commercial products or trade names does not imply endorsement by University of Delaware Cooperative Extension or bias against those not mentioned.

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