Cool Season Grasses

N.J. Ehlke1, and D.J. Undersander2

1Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108. 2Department of Agronomy, College of Agricultural and Life Sciences and Cooperative Extension Service, University of Wisconsin-Madison, WI 53706.
September, 1990.

I. History:

When the United States was settled, the Europeans brought with them seed from the pastures and hay fields of their homeland. As settlers moved west, the grass prairies appeared inexhaustible to the farmers and ranchers who grazed their livestock on the native stands. This was followed by extensive farming operations with little respect for soil and water conservation of the grasslands leading to the destruction of the native prairies and huge losses of valuable topsoil. The production of grass seed did not become an important agricultural crop until after the destructive 1930's Dust Bowl days when the importance of grasslands for conservation was realized. Since that time, grass seed production has become an important agricultural crop primarily in the Pacific Northwest followed by Minnesota and other north central states.

II. Uses:

Cool-season grasses have played an important role in agricultural and horticultural settings. The forage grasses provide pasture and hay for the livestock industry, help prevent soil erosion on land which is unsuited for row crops, provide wildlife habitat and contribute to land reclamation. Turf grasses have long been a major landscape surface in the urban and suburban environment. Home lawns, golf courses, school grounds, cemeteries, athletic fields and parks are some of the major uses of turf grass seed.

III. Growth Habit:

The growth habits of cool-season perennial grasses are similar to annual cereals. There are two types of growth habits associated with cool-season grasses; bunch or rhizomatous. The bunch grasses tend to produce erect tillers which develop and grow upwards within the leaf sheath. The rhizomatous or sod-forming grasses tend to produce procumbent shoots or tillers which break through the leaf sheath and form either rhizomes, stolons or shoots. Most cool-season grasses require vernalization to flower the following year. In most species, this is a combined requirement of cool temperatures and short daylengths. In the fall, perennial grasses produce buds and tillers that overwinter. In the early spring, basal buds at the crown develop into new shoots consisting of unelongated internodes and leaves.

The young shoot, if it has been properly vernalized, will begin to differentiate into an inflorescence. The shoot then elongates to elevate and expose the newly formed inflorescence. The shoot will then flower and be fertilized by wind dispersed pollen, and produce seed.

IV. Environment Requirements:

A. Climate:

Cool-season grass seed production can be a viable alternative to the production of other agricultural crops throughout the north central and midwestern states. However, certain species and varieties have narrow regions of adaption. Climatic conditions such as moisture availability, winter conditions and day length requirements should be considered when selecting the grass species and varieties. Consult your county extension agent about species and varieties adapted to your location.

B. Soil:

For high seed production potential, select an easily worked, well drained soil such as a sandy loam, loam or silt loam soil. Production of Kentucky bluegrass seed has been successful on organic soils.

V. Cultural Practices:

A. Seedbed Preparation:

The factors to consider when selecting a field for producing grass seed include: cropping history; isolation distance from other grass fields, ditches, waterways, and native stands; soil erosion potential; time constraints for land usage; and weed infestations. Soil erosion can be a serious problem when establishing grass seed production fields or when producing grass seed in wide row spacings. Initial seedling growth is often slow which leaves soil bare in the early spring. Land that is subject to surface runoff water during spring snow melts or heavy rains may have serious weed and cross species contamination due to seed being carried into the field by runoff water.

All perennial weeds and annual grass weeds are difficult to control in grass seed fields. Perennial weeds such as quackgrass and Canada thistle should be controlled prior to seeding the grass seed production field. It is also important to control grass weeds, since perennial grass and weed seed are often impossible to be cleaned out of seed lots of other grass species which makes the seed less valuable or even unsalable. Fields with a history of grassy weeds should also be avoided because they provide heavy competition for the newly seeded grass plants.

A firm, well packed seedbed on a level, moderately well-drained soil is desirable. The seedbed should be firm enough that a footprint goes no deeper than 3 in. It is often necessary to use a cultipacker or harrow after the seed is planted to ensure good stand establishment of the small seeded grasses.

B. Seeding Date:

It is important to have adequate soil moisture and soil temperatures for germination and establishment. Cool-season grasses may be planted either in the spring or late summer. If planting cool-season grasses in the spring, seed when the soil temperatures are 40 to 45o F and the fields can be worked resulting in a firm seedbed. If weed competition is anticipated, seed in late summer and control weeds by tillage and/or chemical methods prior to seeding. Problems with late summer and fall seedings may be a lack of sufficient soil moisture and time for adequate growth before frost to properly establish a stand. Seeding in late summer may also reduce or prevent harvesting a seed crop the year after establishment for some grass species.

C. Method and Rate of Seeding:

Cool-season grasses can be established with a companion crop or direct seeded with herbicides. The use of a companion crop is species and grower dependent, and has both advantages and disadvantages. Companion crops will provide soil cover faster than grass crops to protect against soil erosion. Companion crops will compete with the grass seedlings for light, moisture and nutrients, however some grass species are more sensitive to competition from the companion crops while other species may require the extra protection from the companion crop stubble to successfully overwinter (Table 1).

Table 1: Cool-season grass species, seeding rate, seeding method, and special problems or processing  techniques related to seed production potential.
Species Seeding
Suggested Seeding
Special Problems or
Processing Techniques
Kentucky bluegrass 0.5-2.0 CC/DS seed must be debearded
Smooth bromegrass 4.5-6.0 CC/DS no problems
Reed canarygrass 2.0-4.0 CC/DS seed shatters at maturity
Timothy 1.0-3.0 CC/DS no problems
Orchardgrass 3.0-5.0 CC/DS winterhardiness problems
Perennial ryegrass 4.5-6.0 CC winterhardiness problems
Tall fescue 4.5-6.0 DS winterhardiness problems
Fine-leaved fescues 2.5-5.0 CC/DS natural tolerance to sethoxydim (Poast)
1Use higher rates within seeding rate range for broadcast seedings, lower rates within rate range for wide row spacings.
2CC=establish with companion crop; DS=direct seeding.

The choice of a companion crop species also depends upon the grass species seeded and the marketability of the harvested companion crop. Small grains are more competitive than flax with grass seedlings, but the market or farm value of the small grain may make it the better choice. Companion crops allow producers to harvest a crop during the establishment year. However, companion crop competition can reduce potential seed yield of the grass during the first production year. If using a companion crop, the seeding rate should be reduced to minimize competition.

Herbicide and/or cultural control of weeds prior to seeding without a companion crop usually produces a larger seed crop the first production year. Consult your county agricultural agent or chemical representative for herbicide recommendations.

Most grass species are small-seeded requiring a shallow seeding depth, from 3 to 3/4 in. deep. Planting equipment with double disc openers, depth bands and packer wheels usually provides excellent results. Seeding rate is dependent upon the species being seeded and the method of seeding. Grass seed fields may be seeded broadcast or in rows dependent upon available equipment, moisture availability and species. If moisture is limiting in your environment, seeding some species into wide rows should produce a better yield response. The highest seeding rates are required for broadcast seedings and the lowest seeding rates for wide row spacings (Table 1).

D. Fertility and Lime Requirements:

Prior to establishing the grass seed production field, soil test the field to determine fertility levels. It is necessary to maintain adequate levels of P and K according to soil test. Soils should be limed to a minimum soil pH of 5.5. If soil tests or past cropping history indicate a low level of N, apply 10 to 15 lb/acre N prior to planting or in a band when planting. At the 2 to 3 leaf stage, application of an additional 20 to 30 lb/acre N may be necessary. High rates of nitrogen are not recommended because the new grass seedlings are less able to utilize the nitrogen than the competing weed species. On organic soils, no additional N is necessary at establishment.

Cool-season grasses require fertilization to maximize seed yields. Nitrogen fertilization is critical to performance and seed yield of cool-season grasses. On established fields, fall application of nitrogen is recommended in most areas for a number of reasons. Cool-season grasses initiate seed heads in the fall of the year. Proper nutrition will promote seed head development producing higher yields in the succeeding production year. In addition, cool-season grasses often initiate growth early in the spring before fertilizer applications can be made. Fall fertilization also helps distribute the work load on the farm. Fertilizer requirements will vary with the grass species and variety under production. On mineral soils, 75 to 125 lb/acre N are required for optimum seed production. On organic soils, lower rates of N are generally required for seed production, usually 20 to 40 lb/acre N. Previous experience with organic soils is invaluable when deciding on nitrogen fertility rates. Limited research and experience in Minnesota on sandy soils receiving irrigation suggests that split applications of nitrogen may be necessary to obtain optimum growth and seed production. On established seed production stands, there is no experimental evidence showing that seed yields can be increased profitably in northern Minnesota by fertilizing with sulfur or other micronutrients. Boron levels should be monitored carefully however, as B is particularly important for seed production.

E. Variety Selection:

The seed producer should set a goal of optimizing production. The important first step is to select a grass species which is well adapted to the environment, especially the soil type, winterhardiness requirements and moisture conditions. In addition, be sure to consider establishment and production costs; potential yields; seed harvesting, cleaning and conditioning needs; market potential and contract availability. Many different cool-season grasses are adapted to Minnesota and Wisconsin, but potential seed yields and marketability of the seed crops differ significantly. Variety selection is critical if the producer is to profit as a seed grower.

F. Weed Control:

1. Mechanical:

Weed control while establishing seed production fields is critical to obtain a high yielding stand. There are three mechanical options available for controlling weeds in newly seeded fields. Cultivation is applicable only when the seed production field was established in rows. Cultivate when the weed seedlings are small. Shallow cultivation is recommended to prevent damage to the newly seeded grass roots. Be careful to avoid soil ridging when cultivating because it will make harvesting difficult. It may be necessary to cultivate three to five times to control annual grasses and broadleaf weeds. Cultivation in an established stand can help control seedling volunteer grasses and help prevent the stand from becoming sod-bound. Cultivation should be shallow, 1.0 to 1.5 in. to prevent damage to the feeder roots in the established stand.

The second mechanical weed control option is mowing to control annual weeds. Mowing is an excellent option and provides good weed control when done in a timely manner. Mowing also promotes newly seeded grass plants to tiller and produce sturdier plants. Both mowing and cultivation are economical and environmentally sound options for many producers concerned about minimizing chemical inputs.

The last mechanical option open to the producer is hand roguing the field. This option is viable if the seed production field has small areas of high perennial weed infestations. The grower would be advised to rogue out those areas of the field with herbicides or hand labor to prevent weed seed contamination in the seed harvested in succeeding years.

2. Chemical:

There are a few herbicide options for controlling grassy weed species in new and established grass seed production fields. The choice of herbicides is limited and depends upon the grass species seeded, the weed species and the presence of a companion crop.

In established stands, herbicides such as 2,4-D or dicamba (Banvel) can be used to control broadleaf weeds. Apply herbicides according to label recommendations. Generally herbicides should be applied in the fall to prevent potential seed yield losses. Check with your county agricultural extension agent or crop consultant for labeled herbicides to control the weed species in the field.

G. Diseases and Their Control:

Few economically important diseases limit seed production in the north central states. Powdery mildew is the most important disease on Kentucky bluegrass which can cause severe seed yield depression in the north central states. Kentucky bluegrass varieties differ in their level of resistance to powdery mildew. Kentucky bluegrass stand age also influences the incidence and severity of the disease with first year seed production fields suffering the most severe infections. Other foliar diseases of grasses generally do not limit seed production because the symptoms of the diseases such as leaf rust do not appear until later in the growing season on the vegetative regrowth after the seed has been harvested. Smut and ergot diseases have limited production of some cultivars in the west and could do the same in the Upper Midwest.

H. Insects and Other Predators and Their Control:

Insects are usually not a problem in the production of grass seed. However, the capsus bug causes silvertop on all varieties of Kentucky bluegrass and is the major insect pest in grass seed fields in Minnesota. The insect emerges and matures at the same time as the panicles of Kentucky bluegrass. The capsus bug punctures the culm to lay its eggs causing the upper portion of the culm and panicle to die resulting in the silvery appearance of the panicle. The eggs overwinter in the culm and hatch the following year to produce the next generation. Control of the capsus bug is most effectively and economically achieved by burning the field in July. If open field burning is not permitted or the field burned poorly, labeled insecticides can be applied when symptoms of silvertop first appear. Under extreme infestations and favorable conditions, a second application of insecticide may be necessary.

The bromegrass seed midge has been identified in areas of smooth bromegrass seed production, primarily in Nebraska and other midwestern states. To date, the only known host of the midge is smooth bromegrass, and the damage can be devastating to smooth bromegrass seed production. If insects such as the bromegrass seed midge, thrips or grasshoppers are found in economically significant numbers in the grass seed production field, the field should be treated with an appropriate insecticide. Consult your local county extension office for appropriate recommendations to control specific insect problems.

I. Harvesting:

1. Time of Harvest:

Grasses generally do not mature uniformly. Seed ripening begins at the panicle tip and moves downward. The recommended stage of harvest is at the medium to hard dough stage. This is the stage where moderate to hard pressure with a thumbnail will make a mark on the seed. There often needs to be a compromise between maturity and shattering losses when making the decision to harvest to maximize yield.

2. Method of Harvesting:

There are three methods of harvesting grass seed: direct combining, swathing and combining, and seed stripping. The advantages of direct combining are the seed is more mature when harvested and less time and labor are required for harvest. However, the disadvantages of direct combining a crop are the seed moisture content is high requiring the seed to be dried down prior to storage; the crop is more vulnerable to weather because it stands longer in the field; the combining is slower because more green material is run through the combine; and the quality and germination of the seed may be reduced. Swathing and combining the field is the most common method of harvesting grass seed. Swathing and combining has the advantages of faster combining of the field-cured foliage; earlier harvesting because seed cures in the windrow; less seed loss through shattering; and the harvested seed is usually dry and safe to store directly. The disadvantages to swathing and combining are swaths may be scattered or lost by high winds; rains may delay combining causing substantial shattering and potentially lowering seed quality; and more weed seed contamination will be in the grass seed. Seed stripping methods are generally not used with cool-season grasses. The best use of seed strippers is with native prairie grasses. Seed strippers generally produce higher yields and seed quality with less chaff in the seed. Only mature seed is harvested leaving immature seed for a second harvest. The disadvantages are increased harvest and machinery costs, often more soil compaction from the machinery on the field, and high seed moisture content at harvest requiring drying before storage.

For direct combining or swathing and combining harvest methods, a standard grain combine properly adjusted will do an excellent job of harvesting grass seed. The air intake should be adjusted based on seed weight. For light, chaffy seeds, shut down the air allowing only a small amount through the combine. For heavier seeds, slightly increase the air through the combine. The cylinder speed should run about 5000 ft per minute [ft per minute=rpm x cylinder diameter (ft) x 3.14]. The cylinder spacing should be based on seed size. For most grasses, use a 3 in. conclave clearance but for small-seeded grasses such as Kentucky bluegrass, a 1/8 in. conclave clearance is recommended. Make sure the sieves are properly adjusted. If direct combining, adjust the sickle position to cut at least 90% of the panicles while avoiding most of the green foliage. Check the tailings and material from the grain spout often for cleanliness and damage during combining.

3. Residue Management:

Crop residue should be removed following seed harvest to maintain high seed yields. Residue management is critical for maintaining high seed production because sunlight penetration to the crown is critical to grass plants recovering from harvest. For cool-season grasses, three methods are available for removing the residue. The residue can be clipped, raked and baled. Forage quality and feeding value of the residue is low, however it may be satisfactory feed for dry dairy or beef cows. The residue may be burned if burning is allowed by local regulations. If you do burn the residue, be careful to burn on a day when the winds are light so the smoke will rise from the field and not drift into neighboring communities or across highways causing a safety hazard. The residue may also be removed by grazing the seed production field. This practice is risky because grazing does not provide a uniform removal of the residue and livestock may graze the higher quality new growth selectively damaging the stand.

J. Drying and Storage:

Condition the grass seed at a properly equipped processing plant to remove damaged seed, contaminants, and other field trash. Because of the seed size of many grasses, specialized equipment is necessary to clean seed properly. Major marketing decisions should have been made prior to field establishment. It is desirable to have contract arrangements for your seed guaranteeing the marketability of the variety produced.

VI. Yield Potential and Performance Result:

The yield potential of cool-season grasses is dependent upon a number of different factors. The producer should make an informed decision about the species and variety to produce. After choosing a well adapted and high yielding variety, climatic conditions can greatly influence seed yield with moisture being the limiting factor in most north central states. Table 2 contains some performance data on selected cool-season grass species and varieties tested in Roseau, MN between 1980 and 1989. In Wisconsin trials conducted in 1986 and 1987, yields of named smooth bromegrass cultivars ranged from 122 to 575 lb/acre in tests at three locations.

Table 2: Yield performance of selected cool-season grasses. Evaluated in Roseau, MN from 1980 to 1989.
  Seed Yield No. of years1
  mean range  
  ------ lbs/acre ------  
Kentucky bluegrass:      
Aquila 240 24-538 12
Park 366 104-647 17
Rugby 271 98-671 17
Climax 397 127-579 21
Goliath 387 123-760 18
Heidemij 304 30-529 21
Fine Fescues:      
Jamestown 412 128-707 8
Pennlawn 417 98-998 10
Reed canarygrass:      
Palaton 502 202-820 13
Rise 332 98-570 13
Smooth bromegrass:      
Barton 491 149-858 8
Baylor 610 199-1096 5
Perennial ryegrass2 :      
NK-200 819 555-1212 6
Delray 499 343-629 5
Orchardgrass3 :      
Crown 183 0-722 7
Hawk 289 0-858 7
1Number of years used to determine the mean and range in seed yield values from seed production variety trials established in Roseau, MN.
Perennial ryegrass behaves as a biennial in northern Minnesota producing only one seed crop.
Crown was not harvested 3 of the 7 years and Hawk was not harvested 3 of the 7 years because of severe winter injury.

VII. Economics of Production and Markets:

The decision to produce forage and turf grass seed requires a commitment of time and a dedication to quality production. It offers an opportunity for producers to develop a profitable alternative cropping system. Many factors should be considered by the producer before entering into grass seed production. Grass seed production is a long term cropping system and may require more than two years before a seed crop is harvested and profits are realized by the producer. Unlike many annual crops, the value of the seed is dependent upon the market value of the variety produced and usually requires the grower to have a production contract with a seed processor or distributor to insure profit potential.

There are many advantages to producing perennial grasses for seed production. There are no yearly planting costs as with annual crops. No yearly tillage operations are required reducing soil erosion potential after the grasses are established. Chemical and fertilizer inputs are often less than with other commodity crops. Perennial grasses improve the soil texture leading to better moisture penetration. Cool-season grass seed production spreads the work load out more evenly on the farm. Cool-season grass seed production can be an excellent alternative for producers interested in diversification on their farm.

VIII. Information Sources:

Carpenter, J.A. 1988. Divergent Phenotypic Selection for Forage Yield and Nutritive Value Traits in Smooth Bromegrass. Ph.D. Thesis, Univ. of Wisconsin-Madison.

Ehlke, N.J. and L.J. Elling. 1987. Performance of Timothy Strains. Minnesota Extension Service. AG-MI-0425.

Ehlke, N.J., L.J. Elling and W.C. Stienstra. 1987. Performance of Kentucky Bluegrass Strains. Minnesota Extension Service. AG-MI-0424.

Doods, D., J. Carter, D. Meyer and R. Haas. 1987. Grass Seed Production in North Dakota. Cooperative Extension Service, North Dakota State University. 14 AGR-7.

Geldeman, R., P. Carson and J. Gerwind. Fertilizing for Grass Seed Production. South Dakota State University Agricultural Experiment Station. C246.

Holzworth, L.K. and L.E. Wiesner. 1986. Grass and Legume Seed Production in Montana and Wyoming. Bridger Plant Materials Center. Special Report No. 12.

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