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Weeding Out The Bad Seeds

Adapted from the Pennsylvania State University Department of Crop and Soil Sciences – Cooperative Extension. Revised by Peter Landschoot, associate professor of trufgrass science, from Special Circular 168 "Turfgrasss Seed Mixtures," by John C. Harper, II, Extension Agronomist






All seeding rates are measured in pounds per 1000 square feet. If converting to an acre basis, multiply by 43. It is suggested that 3-5 varieties of Kentucky bluegrass be used in the blend or mixture. The resulting increase in diversity will often provide greater overall resistance to turfgrass diseases and other environmental stresses. Photo: Erik Skindrud


As a landscape superintendent, one of the most important steps in turfgrass establishment is the selection of high quality seed or a seed mixture that is adapted to the site conditions and intended use of the turf. Poor quality seed may be low in viability and contain weed seeds as well as undesirable grass species. Consequently, the use of poor quality seed may result in unsatisfactory turf establishment, thus, wasted time, effort, and money. Also, if the species in the seed mixture are not adapted to the conditions at the site, the resulting stand may become thin and subject to soil erosion and weed encroachment. For this column we have gathered descriptions of the components of the turf seed label, as well as suggestions for turf seed and seed mixtures for a variety of site conditions and uses.

The Seed Label:

When purchasing turfgrass seed it is important to read the label to determine the kind, amount, and quality of seed in the container. Most states require by law a tag or label indicating basic information about the seed. This information is as follows.

  1. Name and address of labeler (includes the country, state, and city which are often directly tied to purity)
  2. Lot number
  3. Kind and variety of turfgrass seed listed in order of predominance
  4. Percent by weight of pure seed of each species and variety (percent purity)
  5. Germination percentage (percent viable seed)
  6. Percent by weight of other crop seed
  7. Percent by weight of weed seed
  8. Percent undesirable grass seed
  9. Percent by weight of inert matter
  10. Date on which the germination test was conducted








The name and address of the labeler represents the party responsible for the contents of the container. The lot number is listed so that the contents of the container can be traced back to the original source of production.

Each label lists the species and varieties of turfgrasses in the seed container. By law, the label must contain the commonly accepted name of the turfgrass species and variety in order of predominance when present in excess of 5.0% by weight of the contents of the container. In addition to listing the individual turfgrasses, the label must also provide the percent by weight of pure seed of each species.

The percent germination that is listed on the label for each turfgrass indicates the viability of the seed. Germination percentages are based on the numbers of seed that germinate in a test sample. According to Pennsylvania law, germination tests must have been within the nine month period prior to sale of the seed. A list of suggested minimum standards for percent purity and germination are listed in Table 1.






When purchasing turfgrass seed it is important to read the label to determine the kind, amount, and quality of seed in the container. Most states require by law a tag or label indicating basic information about the quality of the seed. Photo: huntland.com.


Other Seed

The percentage of "other crop seed" in the seed container must be listed on the label. Other crop seed includes all agricultural seed present in amounts of less than 5.0% by weight each. Since some crop seed is not compatible with the desired turfgrasses in the mixture, it is usually best to purchase seed that is low in "other crop seed".

Weed Seed

The percentage of weed seeds should not exceed 1.0% by weight in the container. Good quality grass seed usually contains no more than 0.5% weed seeds.

Undesirable Seed

The seed label lists the percentage of "undesirable grass seed" in the contents of the seed container. By law, turfgrass seed cannot have more than 0.5% "undesirable grass seed" in the container. High quality turfgrass seed contains no undesirable grass seeds.








Seeds or seed mixtures containing timothy, meadow fescue, orchardgrass, tall oatgrass, annual ryegrass or clover are generally not suggested for turfgrass use. Annual ryegrass should be used for temporary turf stands only. Bentgrass may be used for specialized turfgrass areas (golf courses, bowling greens, croquet courts, tennis courts, etc.) but is not suggested for other turfgrass uses.

The percentage of inert material, such as chaff or foreign material, must be listed on the label and should not exceed 15.0% by weight except when fertilizer coatings or pelleting is used to enhance establishment.

Pure Live Seed

Occasionally, turfgrass seed is sold that is low in purity and germination. To compensate for the reduced quality, the seeding rate should be increased. (All seeding rates suggested in section II are based on minimum standards for percent purity and germination listed in Table 1.) The amount of seed required to compensate for poor purity and germination can be determined by calculating percent pure live seed (PLS).













(top and bottom) Illustrating how quality seed can develop the look of a yard in a few weeks time, the landscape superintendent of this area took time to choose the proper turfgrass for his situation. Poor quality seed however, may be low in viability and contain weed seeds as well as undesirable grass species. Consequently, the use of poor quality seed may result in unsatisfactory turf establishment, thus, wasted time, effort, and money. Photos: Erik Skindrud


To calculate PLS, the percentage of pure seed is multiplied by the percentage of germination, and the product is divided by 100. For example, 85% pure seed x 72% germination / 100 = 61% PLS. To determine how much seed to plant, divide the percentage PLS into 100. Thus, in this example, 100/61 = 1.6. Hence, 1.6 pounds of seed with a purity of 85% and a germination of 72% would need to be planted for each pound specified in the desired seed mixture.

Often, seed that is low in purity and germination is sold at a reduced price. One way of determining if the reduced price is really a bargain is to divide the PLS into 100 then multiply by the cost of the seed. A comparison of two seed lots is provided as an example.

Seedlot A

  • (sold at 'reduced' price of $0.95 per lb):
  • PLS = (85) x (60) / 100 = 51%
  • 100 / 51 = 2 lb of seed needed per lb of seed specifed
  • Cost = $0.95×2 = $1.90

Seedlot B

  • (sold at regular price of $1.65 per lb):
  • PLS = (99) x (90) / 100 = 89%
  • 100 / 89 = 1.1 lb of seed needed per lb seed specified
  • Cost = $1.65×1.1 = $1.82

A comparison of actual cost per pound of pure, viable seed reveals that the seed that appeared to be a bargain was actually more expensive.

Suggested Seed Mixtures and Turf Uses:

Listed in Tables 2 and 3 are some suggested turfgrass seed and seed mixtures for different site conditions and uses. Unless otherwise indicated, all suggestions are designed to produce permanent turf.

In some cases, suggestions call for 'turf-type' tall fescues or ryegrasses. This designation is required to distinguish between finer-textured, persistant grasses designed for high-quality turf use and coarser-textured, pasture-type grasses such as 'Kentucky-31' tall fescue or non-persistant grasses such as 'Linn' perennial ryegrass.








A comparison of actual cost per pound of pure, viable seed reveals that the seed that appeared to be a bargain was actually more expensive. An extremely important part of a label is where the seed originates, which often is directly related to price and quality. So the next time you are purchasing seed, if may be more beneficial in the long run to purchase more expensive seed from Oregon for example, as opposed to a cheaper seed made out of the country.



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May 26, 2019, 3:10 pm PDT

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