About Native Iowa Woodland Understory Restoration
Many Iowa woodlands no longer contain the diversity of herbaceous and woody species that once provided soil stabilization, nutrient retention and recycling, soil organic matter, and wildlife food and habitat. Woodlands in private ownership that have been used as pasture for many decades suffer from soil compaction, soil loss, and a ground cover composed of few species, most of which are cool-season exotics like Kentucky bluegrass and smooth brome. Other woodlands that have been protected on private land and in state parks, preserves, and wildlife areas, suffer from severe herbivory by dense deer populations and invasions by exotic trees (like buckthorn, white mulberry, Siberian elm, and black locust), exotic shrubs (like bush honeysuckles, multiflora rose, and Japanese barberries), and exotic herbaceous species (like garlic mustard). The pre-1900 logging history in Iowa followed by over a century of fire suppression, cattle grazing, and numerous introductions of invasives species have significantly altered Iowa's woodlands and greatly reduced their capacities to function within the landscape.
Due to extreme habitat fragmentation, limited dispersal abilities, and complicated germination requirements, many woodland herbaceous species do not re-establish in woodlands when major disturbances are reduced or cease. Life history characters of many woodland species make restoration by seed, a common strategy for prairie and wetland restorations, more expensive, slow, and infeasible because (1) many species produce few seeds, especially less common species, (2) the seed often has exacting germination requirements and low viability, and (3) some species may take many years to reach reproductive maturity, thereby lengthening the time required for a species to spread and increase its population at a site.
The information in this guide can be used to determine which species can be sown directly at a restoration site and which should be started from seed in a greenhouse and subsequently transplanted to a site.
A Guide to Collecting and Germinating Seeds
Our goal for this guide is to provide seed collection and propagation information about shade tolerant herbaceous and woody species that occur in closed canopy forests to savannas in central Iowa, and that for the most part are not included in prairie propagation references. The species list database includes fruit maturation dates for central Iowa, signs of fruit maturation, seed cleaning and storage recommendations, germination requirements, and a restoration potential rating that is based on seed characters and propagation experience.
Our resources page has references for publications on propagation, restoration, woodland and forest ecology and species composition, and plant identification and species distribution. There is also information for additional references, native plant nurseries, and useful websites.
The information in this database has been compiled since 1998 by Cathy Mabry McMullen, affiliate assistant professor at Iowa State University and Larissa Mottl, biological field station manager at Grinnell College. The database will continue to be updated as we learn about the propagation and restoration potential of more species. We invite users to evaluate the information and provide feedback. Input from users will help us expand and improve the database.
- Financial support from Camp Dodge National Guard Military Reservation, Johnston, IA
- Iowa State University, Ames, IA
- Grinnell College, Grinnell, IA