Times Past

More about SLO’s allergenic trees, and what the city can do about it

A young, all-female, pollen-free weeping willow tree in the yard of Bea and Guy Ingwerson at the corner of Craig and Patricia streets in San Luis Obispo.
A young, all-female, pollen-free weeping willow tree in the yard of Bea and Guy Ingwerson at the corner of Craig and Patricia streets in San Luis Obispo. Courtesy photo

It’s been a pleasure hearing about all the people, with their Sunday Tribunes in hand, driving around San Luis Obispo looking at unusual trees on different blocks.

In SLO, most of our seasonal allergies are home-grown.

Pollen coming directly from some of our planted landscapes is making people sick. Because of climate change and global warming, entire plant zones of hardiness have changed across the US. The bloom period (and hence the pollen season) now comes earlier and lasts longer.

The current levels of CO2 (carbon dioxide), higher now than ever before in human history, also increase pollen levels. More CO2 results in increased amounts of pollen shed per tree; in one university study, the amount was increased four fold with higher levels of CO2. All of these are reasons we need to act now to start making SLO more allergy friendly.

At the corner of Craig and Patricia streets in the yard of Bea and Guy Ingwerson is a fine young, all-female, pollen-free weeping willow tree. This tree sheds no pollen, ever, and it cleans air as it traps pollen from nearby male willow trees. The original weeping willow at this spot was planted by the mother of neighbor Lou Guidetti.

The tree there now is a clone of that original tree. Right in front of the SLO Rep theater is a large example of eucalyptus polyanthemos. It is a big, handsome tree, but it is in bloom much of the year and sheds considerable pollen. Of the many eucalyptus species planted in SLO, this is the most allergenic. (Note: some people have found our own locally produced, raw, eucalyptus honey helps with this particular allergy.)

In Santa Maria, Marian Regional Medical Center has practiced allergy-friendly landscaping for 20 years now. They use Tom Ogren’s OPALS plant-allergy scale, and they don’t plant anything that’s highly allergenic.

Ogren worked at many of the hospital’s Earth Day events, and he spoke to a large group of their respiratory nurses and local allergists.

The landscaping at our own local hospitals is an entirely different kettle of fish. If you are coming from downtown and make a right turn into the entrance of French Hospital off Johnson, there are olive trees (very allergenic) on your left side, and on the other side are several male laurel snailseed trees. These are exceptionally poisonous and allergenic.

Next to the snailseed trees is a large bank of English bay trees, all male, all in full bloom now, all shedding pollen. Driving around the parking lots at French, you’ll find a multitude of allergenic trees, There is a large oak in full, massive bloom right now, 10 feet from the ICU unit where I recently received magnificent care.

In the area of The Pacific Medical Plaza, there are numerous very large male podocarpus trees. This species is both allergenic and poisonous, and a chemo drug (Tamoxifen) is made from these trees. Males produce clouds of extremely unhealthy pollen. Correct pruning could keep most of these from shedding pollen, but these trees are not pruned.

The landscaping at Sierra Vista Regional Medical Center is in no way allergy friendly, but it is more diverse and less allergenic overall than that at French. Allergy study is based on prevention. If you are allergic to shrimp or peanuts, don’t touch them, don’t smell them, and certainly don’t eat them. It is the same with pollen allergies and allergic asthma.

Proximity matters: The closer an allergenic tree (or shrub) is to you, the greater will be your exposure. Liz and I both suffer with pollen-allergies, and Liz also is susceptible to asthma. Deaths from asthma have increased by more than 50% since 1980 in the U.S. Thousands die each year, and many are children.

It is far past the time that the City of San Luis Obispo starts to show some real empathy and respect for the thousands of people here who have allergies or asthma. On a last note: The San Luis Ranch and the Avila Ranch housing projects will add more than a thousand new homes.

New housing is needed, but more allergies are not. All new housing in SLO should be landscaped to be drought-tolerant and allergy-friendly.

Learn about Mission San Luis Obispo

I am doing a series of training classes for Mission San Luis Obispo docents from 9:30 to 11:30 a.m. April 27, May 4 and May 11. They are free and open to the public at the mission.

Tom Ogren, the author of three books on allergy-free gardening, contributed to this column.

Dan Krieger is professor of history, emeritus at Cal Poly State University, San Luis Obispo--He is Past President of the California Mission Studies Association, now part of the California Missions Foundation. He can be reached at slohistory@gmail.com.
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