Tallgrass Prairie Center


Developing Iowa Ecotype Seed

Iowa Ecotype Project / Natural Selections seed is developed from remnant prairie accessions

We divide the state into three Iowa eco-zones based on latitude. Differences in temperature and growing season length from north to south are likely to affect the timing (phenology) of plant growth and reproduction as well as their relationships with pollinators.

To create an Iowa Ecotype, the parent seed is collected from several (preferably >10) remnant prairies within a zone in order to maximize genetic diversity.

A map of Iowa counties with three ecozones (north, central, and south) shown as green, yellow, and blue bands; locations of remnant collections for an ecotype are marked.

Seed sourcing and transfer zones are topics of continuing discussion in the restoration community. See for example: Bower, et al. 2014. Generalized provisional seed zones for native plants. Ecological Adaptations 24(5), pp. 913-919

Increasing seed in TPC production plots

For most species, we start seedlings from parent (remnant) seed in the greenhouse. We maintain records of seed treatments, germination, and challenges encountered in producing transplants.

Seedlings (plugs) are transplanted into production plots in spring and managed with weeding, irrigation (if needed), monitoring of pests, and mowing between plots.

Our production fields are inspected annually by the Iowa Crop Improvement Association as part of their Yellow Tag program for source-identified native seed.

University student workers and volunteers transplant seedlings into plastic mulch strip in late spring; seed production plot of spotted Joe Pye weed flowering in summer


Peak seed harvest for most prairie species is from mid-September through mid-October. Depending on the species, yield, and uniformity of seed ripening, we harvest seed by hand or using our Zürn research plot combine.

Student worker stripping milkweed seeds from floss by hand into a paper sack; plot combine harvesting little bluestem in 1/2 acre plot

Seed conditioning and storage

We condition seed using seed cleaning equipment to remove weed seed and other impurities. Equipment in our seed laboratory includes lab-scale: 

  • Brush machine
  • Air-screen cleaner
  • Indent cylinder
  • Belt grader
  • Spiral separator
  • Velvet roller mill
  • Debearder​

Conditioned seed is packaged and stored under cool/dry conditions in a walk-in cooler to preserve longevity.

We maintain records on all seed lots, allowing tracing to their parent source in remnant prairies.

Remnant (parent) seed collections are cataloged and stored separately in a deep freeze for even greater longevity.

Bins of seed stored in humidity controlled walk-in cooler; student holding bag of seed conditioned using laborator airscreen cleaner (in background)


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