The trials are rated by Dr. Stevens on a monthly basis through out the growing season on a scale of 0 to 7 -  0 being a dead plant and 7 being the highest rating given. Vigor (the capacity for natural growth and survival) and floriferousness (bearing flowers in abundance) are rated separately and then averaged together to arrive at the overall rating. To be placed on the Prairie Star list the annuals must receive a rating of 6.0 or higher for two years.