Horseweed has been called marestail in the past. The scientific name used to be eupatorium canadensis. It is a winter annual germinating in September and remaining as a small rosette through the winter. This growth stage is responsible for the name, buttonweed. The seeds blow easily and it is a widespread weed problem in containers as well as field nurseries. It thrives on no-till fields and must be controlled prior to planting.
Photo by Dr. John Meade, weed scientist emeritus
Rutgers NJAES Cooperative Extension