First of all, a word about timing. For grass establishment, It’s all about timing. The right timing can lead to success with ease and the wrong timing can result in a disaster. The first consideration is whether you are about to seed a cool-season or a warm-season grass (see Do I need a cool-season or a warm-season grass?). The best season for cool-season grasses is the late-summer to early fall. In the upper Midwest this will be approximately August 15 to October 15. The further south you are in the cool-season zone the later you can go and the further north you are, the earlier you will have to seed. The reason for this is primarily centered around weeds. The biggest problem in a cool-season lawn is the competition from warm-season weeds, like crabgrass and goosegrass. These weed species germinate in the spring and thrive through mid-summer. They are annuals, so they simply die in the fall and germinate again from seed in the spring. Cool-season grasses are the opposite. They thrive in the cooler temperatures of fall and spring and struggle in the summer. Seeding cool-season grasses in the spring will result in warm-season weeds taking over. You will not even see your cool-season grasses until fall. The warm-season weeds do not germinate later in the year and they are not a problem in a fall seeding. This gives the cool-season grasses all fall to fill in. They also start growing in the spring before warm-season weeds germinate, giving them another advantage over the weeds. This doesn’t mean that you cannot seed cool-season grasses in the spring or summer, but the success rate will be much lower than seeding them at the right time.

Warm-season turfgrasses are best seeded in the spring, just before their ideal growing season in mid-summer. Depending on how far south you are, this will usually begin in late May and will go well into July. It will not work to seed warm-season turf in the fall. Most of the seed will not germinate until spring and what does germinate will have a very short growing season in late summer.

The process needed to prepare the seed bed will depend on the initial condition of the site. If there are low areas, where water can gather, some rough grading will be necessary to assure proper surface drainage. On new construction around homes, be sure that the site does not slope toward the foundation of the house. This can result in long-term problems with water around the foundation. Another problem with new construction can be poor quality soil on the surface. If sub-surface clay soil from the basement is on top, the grass will not do well. In that case, placing 4 to 6 inches of topsoil on the site may be necessary. If the site has suitable soil, but is compacted by construction equipment, rototilling the site to a 4 to 6 inch depth will be necessary to loosen the soil for proper plant growth.

Never bury construction debris like rocks or pieces of wood in the seed bed. This is a common mistake. Later, when the grass comes up, the root system will be shallow over the buried objects and the grass above it will not do well, particularly in drought conditions.

Once proper slopes and surface drainage have been established, the site will need to be smoothed just before seeding. This can be done with a garden rake on smaller sites or with a drag mat on larger areas. Make sure the final seed bed is as smooth as possible.

This is the time to apply the starter fertilizer. This will be a special fertilizer high in phosphorus. See (What is a starter fertilizer?) in this series. It should be left on the surface and lightly worked in with the seed.

If time permits, a chemical soil test will be useful. This service may be available through your local county extension service. If not, there are private soil testing labs in many parts of the country. The results of the soil test will tell you a lot about the nutritional status of the soil and will be useful in determining whether lime, or some other additive may be required. The other information from the test will also be useful in determining fertilizer needs later for the mature turf.

When seeding, concentrate on seed-soil contact. This is best done by applying the seed to the soil surface and then raking or dragging it in lightly. Seed can be applied in several ways. Simply spreading it by hand can be effective for small areas. Try to spread it as uniformly as possible. For large areas, there are both broadcast and drop spreaders. They can both be effective, although the drop spreader, where the seed is released from the bottom of the hopper close to soil surface, generally provides the best results. Lighter seed particularly will tend to be blown by wind when released from the broadcast spreader and may not provide the uniformity desired. For very large areas, there are tractor drawn drill seeders that can effectively apply seed uniformly, at the desired depth.

The depth from which seedlings can emerge will vary by species. The smaller the seed, the closer it needs to be to the soil surface. Large seed can be buried by an inch or more of soil and still emerge. Kentucky bluegrass has a small seed and is generally lightly raked into the surface, whereas tall fescue has a much larger seed and can be buried by an inch or more of soil and still emerge as it germinates. Check with your seed dealer if you are not sure about the depth of seeding for your particular species.

Grass seed of various species will vary a lot in the amount of seed that is needed per unit area. The two primary considerations are the size of the seed and the growth habit of the grass. Grasses with small seed have many more seeds per pound than larger seeded grasses. Kentucky bluegrass has 1.6 to 2 million seeds in a pound, whereas a larger seeded species like tall fescue may have only 178,000 to 234,000 seeds per pound. Each seed will produce a plant, and small seeded species can be seeded at lower rates.

The growth habit refers to whether the grass has rhizomes or stolons to spread the grass after it has emerged, or whether it is a bunch-grass and will spread very slowly by the growth of plant parts. A rhizomatous grass like Kentucky bluegrass spreads rapidly once it matures and can be seeded at lower seeding rates. A bunch-grass like perennial ryegrass has to be seeded at much higher seeding rates than bluegrass because of the lack of spreading plant structures.

Follow the recommended seeding rate for the grass that you will be applying to the area. There is no reason to apply too much seed. It wastes money and the results will not be as good as seeding with the proper amount. You also want to be sure that you have enough seed to successfully establish the grass. Some seeding rates for common turf species include: Kentucky bluegrass 1 to 1.5 lbs/1000 sq. ft., perennial ryegrass 7 to 9 lbs/1000 sq. ft., fine fescues 3.5 to 4.5 lbs/1000 sq. ft., tall fescue 7 to 9 lbs/1000 sq. ft., bermudagrass 1 to 1.5 lbs/1000 sq. ft., and buffalograss 2 to 3 lbs of burs/1000 sq. ft.

For more information on seeding new areas, see (https://www.extension.iastate.edu/turfgrass/establishing-lawn-seed)

Nick Christians, University Professor of Horticulture, Emeritus, Iowa State University

books: http://www.amazon.com/Nick-Edward-Christians/e/B001H6SB7A/ref=ntt_dp_epwbk_0

turf blog: http://www.iaturf.blogspot.com/

Fundamentals of Turfgrass Mgt. 5^th ed http://www.wiley.com/WileyCDA/WileyTitle/productCd-1119204631.html

Web site: https://www.hort.iastate.edu/directory/nick-christians/

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