Framework / Assessment USDI Indicators of Rangeland Health (2000) Summary Adequate seed production is essential to maintain populations of plants when sexual reproduction is the primary mechanism of individual plant replacement at a site; however, annual seed production of perennial plants is highly variable. Comparing number of seedstalks and/or number of seeds per seedstalk of native or seeded plants (not weeds or invasives) in the evaluation area with that produced on the associated ecological reference area (ERA) can be used to assess seed production.