Production Topic - Seed Cleaning
When producing foundation ecotype seed, the TPC’s goal is to provide pure, viable seed that retains the range of genetic diversity found in Iowa remnant prairies. We work to avoid unintentional selection at each production step, including seed cleaning. We regularly inspect each fraction of cleaning “trash” and, if needed, run it back through with adjusted settings to capture good seed that is either larger or smaller than average.
White meadowsweet, Spiraea alba, is a good example. We find abundant smaller, but filled and healthy-looking, seed in the aspiration fraction when air-screening this species. We are able to capture this material by adjusting the settings for a second (or third) pass.
We find that it’s challenging to separate Spiraea alba seed from small leaf fragments. This year, we found two tips that seem to improve the purity, though we haven’t had it tested yet:
1) We eliminated the brushing step since the dry capsules release nearly all seed if harvested at maturity, and this resulted in less fine “trash”
2) After air-screening, we ran the product through a set of soil sieves which provided a finer separation.
For more information on the importance of seed cleaning practices in maintaining genetic diversity of seed for restoration, see the article on Native Seed Cleaning and Testing in the special issue of Restoration Ecology devoted to Standards for Native Seeds in Ecological Restoration.