Cooperative Extension
MG Manual Home

  MG Manual Reference
Ch. 12, pp. 14 - 18

Selection of the proper turfgrass variety for a lawn, based on the site and intended use is the major factor in the successful performance of a lawn. If you have selected a turfgrass which will be established from the seed, the next question is to acquire the seed for planting. In order to better understand what's in the "seed bag," you should be able to read the "seed tag." The seed tag is a legal document which contains important information about the integrity and condition of the variety(s) and other materials sold to you as the final product. For seed that travels from state to state, Federal Seed Act (FSA) requirements must be met which require the following information:
  1. Seed Lot Number: used for permanent identification.
  2. Kind of Seed: accepted or common crop name. Examples are perennial ryegrass, tall fescue, common bermudagrass.
  3. Percent Pure Seed: this is the amount of seed by weight for each variety. This includes the name(s) of the variety or varieties included. If no variety is claimed, then VNS (variety not stated) appears on the tag.
  4. Other Crop Seed: this includes other unnamed varieties of the desirable turfgrass species, or other species of other grasses or crop seeds. This can be up to 5% by weight of the seed bag.
  5. Weed Seed: this is the percent by weight of the seed bag which contains either noxious weeds, and/or other weed seeds. If noxious weeds are present, then usually strict limits are imposed as tolerance limits.
  6. Inert Matter: this includes the amount of non-seed materials by weight. Soil particles, broken seeds, awns and short stems are items included in the percent inert matter.

Note: the amount of pure seed, other crop seed, weed seed and inert contents equals 100%.
The seed tag also bears information regarding the germination capability of the seed, which is tested under strict laboratory conditions for each species.
The percent germination indicates what percent of the actual seed itself will germinate (under optimum conditions). The date (month and year) of the germination test is included on the seed tag. For seed which travels as interstate commerce (essentially all our cool season turf grasses are from other states) the germination test information is applicable for a period of five months after the test month. For instate seed produced in Arizona (bermudagrass) the germination test is valid for nine months.
Special seed treatments (if applicable) must be noted on the tag as well. These treatments include any chemical or temperature treatments to break seed dormancy (potassium nitrate/cold storage, etc.). Any fungicide treatments to the seed would be included here as well.
If the variety has an application for, or has received a PVP (Plant Variety Protection) certificate, this too appears on the tag.
Blue Tag Certified Seed

This is the highest quality seed available. In order for turfgrass seed to achieve blue tag status, the following conditions must be met:
  1. Fields have been planted with either approved foundation or breeder seed, or established with certified planting stock.
  2. Variety is worthy of certification, or describable by the originator.
  3. Production fields meet sanitation standards and are grown with proper isolation distances (from other plants of the same species).
  4. The production fields have 0.03% or less off type plants.
  5. Minimum standards for purity are met.
  6. Other grass contamination limits are met.

These conditions when met, insure the buyer that the best quality seed is available to them.
Pure Live Seed

It is important to take into consideration the actual amount of seed which can be expected to germinate.
Two components of information on the seed tag allow you to do this. These two items are (1) the percent pure seed, and (2) the percent germination. If the seed is 90% pure, then the remaining 10% is not seed at all. If the germination is 85%, then on average 8.5 out of ten seeds will germinate. The remaining 1.5 out of ten seeds will not germinate. In order to find out how much "good seed" will at maximum "germinate," you must calculate the PURE LIVE SEED (PLS) INDEX. To do this, simply multiply the percent purity times the percent germination.
From our discussion example above...
PLS = % purity X % germination
(0.90) X (0.85)
= 0.76, or 76%
This means that 76% of the product by weight will germinate, under the best conditions. So a 50 pound bag of perennial ryegrass seed will have a PLS content of 38 pounds. Knowing this, the actual amount of seed required must be adjusted by the PLS content.
For example, a 3000 square foot lawn is to be overseeded at 20 lbs./1000 square feet with annual ryegrass. This quickly figures to a convenient 50 pounds of seed required. But, since the PLS content is 76% (0.76), we must now adjust and calculate how much of the actual product we need.
50 lbs. divided by 0.76 (PLS) equals 66 lbs.
We now need 66 pounds of seed which has a PLS index of 76% to seed 3000 square feet of turf at the 20 pound seed rate.
Both tall fescue and perennial ryegrass seed may or may not contain a beneficial fungus inside the seed. The seed is called the ENDOPHYTE. This endophyte fungus causes tall fescue and ryegrass plants in the lawn to produce natural chemical substances inside the plant. These chemicals repel above ground feeding insects. These include chinch bugs, flea beetles, armyworms, cutworms and aphids, etc. However, below ground insects (grubs) are not affected. The seed tag should say if the seed is either ENDOPHYTE ENHANCED or ENDOPHYTE FREE. If it does contain endophyte, it should say what percentage of the seed is infested. While endophyte enhanced seed is good from a lawn standpoint, it is unfavorable to use the same lawn seed for pasture. Do not establish a pasture from endophyte containing seed. Use it for lawns only.
Turf may be established from seed, sprigs, plugs, or sod. The method depends on the type of grass desired, the environmental conditions, time constraints, and financial considerations. The same basic requirements for seed bed preparation, fertilizer application, and watering apply for both seeding and vegetative establishment. After the new lawn is established and growing well, begin a good, comprehensive maintenance program to keep it healthy and attractive (See maintenance calendars).
Soil quality and preparation are important steps in planting a new lawn. Begin by removing the existing vegetation. Use a non-selective herbicide like glyphosphate (Round-Up) to kill the weeds that are growing. The weeds must not be moisture stressed when they are sprayed. Let Round-Up dry on leaves for 12 hours. Dig into the soil and get a feel for the soil particles. Is it mostly sandy, loamy, or very fine--clay like. Sandy soils drain quickly, and have good root growth. The clay soils tend to drain poorly and become compacted. Soils which have 50-60% sand and the rest smaller particles are best for a lawn. It's much easier to add fine soils to coarse sandy-soils, than to add large amounts of sand to dense clay soils. Examine the soil and overall suitability of the site. Is the soil heavy (clay) or light (sandy)? Does the soil contain gravel or large stones on the surface, or just below the soil? Were any items "dumped" on the site such as chemicals, gas, oil, construction materials, cement or gravel? If so, these should be removed. A soil test should be done in order to add proper fertilizer types and amounts. The area should be roto-tilled if the soil is compacted. Most soils can be temporarily modified for planting by adding organic matter such as plant parts, shredded bark, horse or cattle manure. To properly add organic matter, do the following:
  1. Wet the soil and let it drain 2 days.
  2. Roto-till the soil as deep as possible.
  3. Wet the soil again and let it drain 2 days.
  4. Roto-till again.
  5. Add the organic matter on top of the tilled soil.
  6. Roto-till again as deep as possible.

Search Index Comment

This site was developed for the Arizona Cooperative Extension, College of Agriculture, The University of Arizona.
© 1998 The University of Arizona. All contents copyrighted. All rights reserved.