Building a Low-Allergen Plant Palette

by Michele Richmond, PLA, ASLA, SITES® AP, LEED® Green Associate

Scanning electron microscope image of pollen grains
Pollen from a variety of common allergenic plans including morning glory, sunflower, lily, and castor bean (a 10 on the Ogren Plant Allergy Scale (OPALS)). The image is magnified around x500. / image: Dartmouth College Electron Microscope Facility

Can you plant a site with species that cause little to no allergies in patients? That was the specific request from our client for a site comprised of a community healthcare clinic and workforce and affordable housing. Many of our client’s patients are traumatized children with asthma and allergies. The goal of the building and landscape design was to create a safe place allowing for positive experiences for children coming to the clinic. In this context, a single allergy attack removes children from this safe space and can set back their recovery. So, what to plant?

Allergies and Asthma in America

Today, more than 50 million people in the US have allergies and asthma [i], including hay fever and respiratory, food, and skin allergies that can come from plants in our landscape. Allergies can be a onetime event or a constant reaction to pollen. Currently, allergies are the sixth leading cause of chronic illness in the US, resulting in 200,000 emergency visits a year [ii] and costing more than $18 billion annually [iii]. In Washington State, asthma is the most common chronic illness for low-income children. Asthma cases have doubled in the population at large and quadrupled among low income families in the last thirty years [iv].

While allergies largely cannot be prevented, we can lessen allergic reactions. As children, we learn to identify poison ivy and oak to avoid contact. As adults, we learn to check pollen counts [v] daily to determine if we need to take allergy medicine. We learn to identify and keep a healthy distance from plants that are the worst offenders to offset symptoms.

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