Our pollen page has information on specific plants and a pollen calendar showing regional information on common pollens. For additional information, the following sources may be helpful.

street trees

  • Some towns and cities have a database of city-owned trees and their locations. Ask your local parks and recreation department.
  • Often, nurseries and professional landscapers can tell you what’s being planted in local neighborhoods.
  • Garden clubs.
  • Landscape and gardening books.


  • In addition to the Internet sources listed above, take a look at Iowa State University’s Weed Biology Library
  • State and federal agricultural departments often have weed scientists or extension agents who are familiar with the many weeds that impede local agriculture.
  • Gardening books are readily available and often have extensive guidelines for the identification of weeds.

native plants

  • Universities and colleges often have a systematic or taxonomic botanist on staff. If they can’t help you directly, they can usually lead you in the right direction.
  • Various private industries keep botanists on staff.
  • Every state maintains taxonomic texts, describing vegetation native to the state. Details on flora may include abundance, location, and blooming season. Publications may also include non-native plants that have become endemic, such as the Brazilian Pepper Tree in Florida, Pampas Grass in California and Texas and, of course, the ubiquitous Russian Thistle. Your state may be able to provide you with a text or botanical survey paper that specifically covers your immediate focus of interest.
  • Native plant societies are additional resources. These volunteer groups’ interests vary from cultivating native plants and species preservation to cataloging vegetation growing beside local hiking trails.
  • A quick web search can reveal valuable links. Sometimes using the Latin name of the plant helps provide great finds. The American Academy of Allergy, Asthma and Immunology’s (AAAAI) National Allergy Bureau produces recent pollen count information by locale. The AAAAI also sells an annual pollen count report derived from the Aeroallergen Network. Another valuable link is The Virtual Foliage  site from the University of Wisconsin-Madison’s Department of Botany, which provides many images of native plants and plant communities.