Emily Skelton, Seeds of Change
This is an Organic Seed Resource Guide article.
It is important as a seed grower and seed buyer to understand that weed seeds can be distributed along with crop seed. Noxious weed seed contamination of crop seed is regulated by state and federal regulations. For more information, see the eOrganic article Weed Management in Organic Seed Production. The table below describes weed seeds commonly found as contaminants in vegetable seed lots and the methods used to screen them out.
|Crop||Weed species||Listing||Difficult to remove due to:||Method used||Degree of success|
|Basil||Brassica spp (prohibited)||18/lb||Same color, size, similar shape||Belt grader||Fairly successful but a very slow process|
|Calendula||Black bindweed (Polyganum convovulus)||2/lb||Same color, size||Screens, Indent Cylinder||Not very successful|
|Clover, Yellow Blossom Sweet||Brassica spp||18/lb||Similar size||Screen, indent Cylinder||Not very successful|
|Endive||Brassica spp., wild radish, Canada Thistle (Cirsium arvense)||18/lb, 12/lb, prohibited||Similar size, color||Indent Cylinder||Fairly successful|
|Lettuce (light seeded only)||Crabgrass (Digitaria sanguinalis)||27/lb||Similar color, shape, size||Indent Cylinder||Fairly successful|
|Lettuce||Wild lettuce (Lactuca pulchella)||prohibited||Can't differentiate||None||Not very successful|
|Mexican Sunflower||Johnsongrass (Sorghum halapense)||prohibited||Same size, similar shape, color||Fanning, screening||Not very successful|
|Onion||Black Bindweed (Polygonum convovulus)||2/lb||Similar size, color||Satake color sorter||Color sorter successful, only with green seed coat intact|
|Peas/Beans||Black nightshade (Solanum nigrum), White horsenettle (Solanum elaeagnifolium) berries||9/lb, prohibited||Similar size||Gravity table||Very successful|
|Dill||Black nightshade (Solanum nigrum), White horsenettle (Solanum elaeagnifolium)||9/lb, prohibited||Similar shape, color||Screen, Indent Cylinder||Not very successful|
|Zinnia||Johnsongrass (Sorghum halapense)||prohibited||Similar shape, size||Screens, Indent Cylinder||Indent cylinder fairly successful|
This publication contains information about the various state labeling requirements and prohibitions of noxious-weed seeds and shows the botanical names and common names according to the law and regulations of the particular state in which the seed is noxious. It is the responsibility of seed dealers to know the requirements of state laws and the changes in those laws.
This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.