News Article
MN Dept of Agriculture - January Weed of the Month: Are There Any Weeds In My Seed?

January 3, 2019

January Weed of the Month: Are There Any Weeds In My Seed?

Michael Merriman, Minnesota Department of Agriculture

A pile of seed

In spring, before home owners are ready to seed their lawns, gardeners are prepared to sow their plots, and farmers can fire up their planters, these individuals need to purchase the seed needed for their projects and livelihood. Buying seed can seem like an overwhelming process for an inexperienced homeowner walking down the seed aisle at the local home and garden store. In the seed aisle there are often numerous companies selling dozens of different types of seed. So, what’s inside of those bags of seed? Does the seed contain any weed seeds?

If you flip over your seed bag, you should see a label that contains a plethora of information. Although it looks like a lot at first, there are a few key things to look for. The company or “labeler” indicates who put together that seed bag and labeled it. The germination tells you what percentage of seed is likely to sprout into a seedling if planted. The “kinds” on the label are the different species of seed that are present in the seed bag.

Purity is the percentage of each component that is present in a seed bag and ensures that 100% of the contents of the seed bag are accounted for on the seed label. These components include the purity for each species of seed if there is one kind or numerous kinds in a mixture, inert matter, other crop, and weed seed. Percentages of each of these components are determined when the seed is tested by a seed lab.

NAME: Sunny North

NET WEIGHT: 20 lbs







Tall Fescue





Perennial Ryegrass





Kentucky Bluegrass









TEST DATE: 01/18

SELL BY: 02/19

LABELER NAME AND ADDRESS:     Green Grass Company

                                                             123 Lawn St., Seedtown, MN 55555

The above figure is an example of a seed label and the information on that label is described below:

  • Pure seed is the percentage of each kind (species) or percentages of each kind of seed if the bag is a mixture. For example, a lawn mix may contain 30% Fescue, 30% Perennial ryegrass, and 35% Kentucky bluegrass.
  • Inert matter is anything inside of the bag that is not seed including chaff, broken seed pieces, plant debris, soil, i.e. anything that can’t be removed from the seed when it is cleaned and conditioned as part of seed processing. It may also include coating to make it easier to plant and better able to germinate.
  • Other crop seed includes other species of seeds that are unintentional contaminants in the seed bag and are commonly sold as crop seed in a given type of seed. These other crop seeds are not considered detrimental.
  • Weed seed includes seeds that are identified as weeds in agricultural, natural, or other settings. The classification as a weed seed is determined by the Association of Official Seed Analysts (AOSA) Rules for Testing Seed and percentage may include noxious weed seeds. In Minnesota the percentage of weed seeds should not exceed 1% for the contents. Note that this definition of weed seed should not be confused with Minnesota noxious weeds, a listing of plants considered to be noxious in Minnesota.

Weed seeds include common and noxious weeds where noxious types may either be restricted or prohibited noxious weeds seeds. Restricted noxious weed seeds are ok if they are below the specified acceptable rate. If a prohibited noxious weed seeds is present, however, the seed would not be legal for sale. Both restricted and prohibited weeds seeds are determined based on the All-States Noxious Weed Seed List and should be listed on the label by name and number per pound of seed.  Minnesota recently added Palmer amaranth as a prohibited noxious weed seed; any seed containing this weed seed is illegal to sell in Minnesota. A seed analyst looking for noxious weed seeds can’t visually identify Palmer amaranth. All seeds in the genus must be tested genetically to determine if this prohibited noxious weed seed is present. The Minnesota Department of Agriculture helped facilitate the development of this genetic test to prevent the spread of this herbicide-resistant, aggressive weed and protect agriculture in Minnesota.

The Minnesota Department of Agriculture Seed Program monitors seed for sale in the state to make sure that it is labeled truthfully and accurately. Seed inspectors and County Agricultural Inspectors collect approximately 1600 annual samples from seed that is available for sale throughout the state, and submit the samples to the state seed  lab for a purity/noxious and germination tests. The results obtained by the lab are compared to the label to determine whether the label is truthful. 95% of the seed for sale in the state is truthfully labeled.

If you are worried about weed seeds, read the seed label. It will tell you what percentage of the seed is weed seeds. It will also identify any noxious weed seeds present. Small seed packets produced for home gardeners are not required to be labeled with this information as long as the pure seed percentage is greater than 90%, inert matter is less than 10%, or if other crop seed, weed seed, or noxious weeds seeds are not present. If you have any concerns about the label, please contact MDA’s Seed Regulatory Program


Click here to download the image.

Caption: A seed analyst must be able to visually identify all seed to species including common and noxious weed seeds. In some cases it is not possible to identify noxious weeds by visual analysis only. For example,  a genetic test must be used to identify Palmer amaranth.


MEDIA: For more information on Weed of the Month, contact Allen Sommerfeld, MDA Communications, at or 651-201-6185

Link to the bulletin on the MDA website: