Thomas L. Ogren

  • Currently serves as President of the non-profit
  • Health, allergy, horticulture consultant for cities, schools, hospitals, pharmaceutical companies,  designers, nurseries, and occasionally for individuals
  • Expert in identifying the sex of landscape plants.
  • Originated OPALSTM (Ogren Plant Allergy Scale) – the first plant-allergy scale; measures the allergy potential of all garden and landscape plants and is now used by, among others, the American Lung Association and the USDA Urban Foresters.
  • Author of “Allergy Free Gardening” and “Safe Sex in the Garden.”
  • Recently completed a coast-to-coast urban forest allergy-audit of the eleven major cities in Canada for Johnson & Johnson.
  • Former co-owner of Ogren Brothers Nursery in Minnesota.
  • Education: California Polytechnic State University (MS – Agriculture, Horticulture)


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