The pollen count can be lowered if people plant more female plants and fewer male plants, says horticulturist Tom Ogren. He says male plants have been popular because they don't produce messy fruit or seed pods -- but they are responsible for most of the pollen in the air. It's better to plant females or plants with both male and female parts, Ogren says, since the pollen doesn't spread as much.
Robert Siegel talks with Tom Ogren, author of Safe Sex in the Garden and Allergy-Free Gardening. Ogren developed the OPALS (Ogren Plants Allergy Scale) measure from his research with the USDA.