Seed Cleaning and Conditioning

Prior to storage and sale, it is necessary that wildflower seeds are thoroughly cleansed of dirt, stems, trash, and unwanted seeds, such as noxious weed seeds. Mechanical cleaning methods help remove trash and other debris for product purification. Because wildflower seed varieties vary in shape, size, and texture, there are many different methods for wildflower seed cleaning and conditioning.

Some wildflower seed varieties require threshing in a “de-winging” or scalping machine (Parris, Shock, Feibert, & Shaw, 2010). This machine assists in removing seeds from flowering structures that were not separated during harvest. A hammermill machine is designed to remove hulls and open seed pods, while air-screen cleaners and air separators remove finer materials. Velvet roll separators aid in segregating unwanted weed seeds from wildflower seeds, but may sacrifice some wildflower seed in the process (Pfaff, Gonter, & Maura, 2002). If necessary, seeds may be cleaned again using a small clipper seed cleaner or a gravity separator to segregate seeds from fruitcases (Pfaff, Gonter, & Maura, 2002). Seeds should be cleaned to 95% purity (Parris, Shock, Feibert, & Shaw, 2010). If tasks cannot be completed mechanically or if the seeds are fragile, manual cleaning methods must be employed to preserve seed quality (Shock, Feibert, Saunders, Shaw, & Sampangi, 2011). See Florida Native Seed Production Manual for more information.

Following the cleaning process, forb seeds must be conditioned in preparation for storage and eventual marketing. The conditioning process removes moisture from seeds to prevent rotting while in storage. Seeds should be dried to a moisture content of 15% or less using artificial heat via low volume air drying, if necessary. In low humidity environments, some native wildflower seed varieties can be stored up to six years in bags (Shock, Shock, & Feibert, 2012).

Another pertinent aspect of wildflower seed production involves monitoring the purity of the product. For quality control purposes, seeds should have a minimum germination ability percentage of at least 75% (obtainable through testing) (Parris, Shock, Feibert, & Shaw, 2010). Producers of certified seed in Oregon must be in accordance with Oregon State Seed Certification Service rules and regulations (Cornforth & Ogle, 2002).


  • Cornforth, B., & Ogle, D. (2002). Seed Production Standards for Conservation Plants in Eastern Oregon. USDA- Natural Resources Conservation Service
  • Parris, C. A., Shock, C. C., Feibert, E. B. G., & Shaw, N. L. (2010). Sulphuer-flower Buckwheat Eriogonum umbellatum (ERUM) (pp. 1–3). Malheur County Experiment Station, Ontario, Oregon; Oregon State University
  • Pfaff, S., Gonter, M. A., & Maura, C. (2002). Florida Native Seed Production Manual
  • Shock, C. C., Feibert, E. B. G., Saunders, L., Shaw, N. L., & Sampangi, R. S. (2011). Native Wildflower Seed Production With Low Levels of Irrigation. Malheur County Experiment Station, Ontario, Oregon; Oregon State University