Acer rubrum female Help us by asking the staff at your garden center or nursery if they have allergy friendly plants, shrubs or trees.

See the SAFE Gardening Brochures by clicking here 

See the Queux Patio Plants Leaflet by clicking here

See the Milkweed Highway Rack Card by clicking here

See the Indoor Plants Allergen Rating by clicking here

See the Students Deserve a Healthier Schoolyard Flyer by clicking here

See the Seasonal Flowering Plant Chart - 2019 by clicking here

We encourage you to copy any of the information above

and share it with others.


A Plant’s Sex

The sex of a plant often influences pollen allergies.  

Plants that are entirely male:

  • Are often used in landscaping, especially in cities, commercial sites, parks, and schools because they do not produce fruit or seeds and result in a visually clean landscape.
  • Always release abundant pollen into the air.
  • Negatively contribute to the incidence and severity of asthma and allergies, especially in children.

Plants that are entirely female:

  • Some (but certainly not all) may produce fruit or seeds that can be large and messy.
  • Clean up pollen by serving as air filters, as natural pollen-traps.
  • Never produce any pollen and are truly allergy-free.
  • Whenever female plants are used to replace male plants, this reduces the incidence of exposure, and the severity of local asthma and allergies.

Unfortunately, at this time there are few plant tags that specify if a plant is male or female or how the plant rates on the OPALS® scale.  Note: The Ogren Plant-Allergy Scale (OPALS) is a rating system for plants and allergy that rates plants on a 1 to 10 scale, with 1 being the best, most allergy-free selections and 10 being the worst. The complete scale is in the book Allergy-Free Gardening, and the newest, most updated scale will be in the Allergy Fighting Garden (Ten Speed Press & Random House), due in stores 2/17/15.

Pollen Counts

Urban pollen counts have been increasing over the last 15 years at alarming rates and are predicted to double by 2040.  Approximately 20% or more of the American population suffers from pollen allergy (   Multiple factors contribute to this:

  1. Increasing CO2 that causes plants to grow faster.
  2. Increasing heat due to climate change/global warming.
  3. The continuous planting of more and more allergenic plants and trees in cities.
  4. Increased hardscapes that do not allow pollen to settle and merge into soil.
  5. Increased use of male plants that trap no pollen and thus recirculate it on to hardscapes.

Pollen counts are highest during the day when the sun is out.  It is important that where we spend our days, especially outdoors, contain the least amount of pollen.  For children, this is often school.  Yet our schools are often planted with highly allergenic, non-fruiting male trees designed to keep the area clean and tidy and to keep maintenance costs low (unfortunately this raises allergies & asthma and increases the medical costs).

Allergies and Asthma

Allergies are the major cause of allergic asthma and the most common form of asthma.  Sixty million Americans suffer from asthma and allergies.  Asthma is the number one chronic childhood disease, and allergies are the fifth leading chronic disease in the United States.

Avoiding, and thus controlling one’s allergies seems elusive and mysterious because pollen, the source of seasonal allergy, is invisible to the naked eye.  It is in the air we breathe, but is rarely seen or smelled.  It is created by different plants in different seasons; trees in winter and spring, grass, shrubs, perennials and weeds in summer and fall, so in many areas can be present almost year round. 

It is also important to prevent asthma because of its genetic component.  Children have a 33% chance of developing asthma if one parent has it, but a 70% chance if both parents have it.  Asthma is one of the most common and most costly diseases.  According to the Asthma and Allergy Foundation of American every single day:

  • 44,000 people have an asthma attack
  • 36,000 kids miss school due to asthma
  • 27,000 adults miss work due to asthma
  • 4,700 people visit the emergency room due to asthma
  • 1,200 people are admitted to the hospital due to asthma
  • Average length of stay: 3.6 days
  • 9 people die from asthma

The asthma rate has increased from 34 cases out of 1,000 people to 52 cases out of 1,000 people in just twelve years (  Approximately 20% of Americans suffer from pollen allergy (AAAAI).  Approximately 8 % of American adults and 9.5% of children have asthma, though asthma affects 11% of California children (age 0 – 17).  New diagnoses of asthma are increasing at the fastest rate in our youngest population, children aged 0 – 4.  Approximately 30% of asthma is triggered by pollen and a great deal more is suspected to be caused by allergies, but few young asthma patients are allergy tested (CAP-2010).

Avoidance and Prevention

Avoidance and prevention therapy are the best approach for both allergy and asthma.  Lung damage resulting in asthma is irreversible. Proximity pollinosis in lay terms means: “the closer one is to the source of the pollen, the greater will be the exposure,” thus, the need for allergy-friendly landscaping in all urban areas.   An example of proximity pollinosis can be seen in the following photo of a male maple tree.  The tree is shedding a great deal of pollen that can be easily seen against the backdrop of the dark pavement of the parking lot.   




2021  Safe Gardening  
Affordable Website Design by Affordable Website Design