Better Off Well


Why We're Sneezing More: A Look at What's Happened To Plants

allergy book

My son was miserable this spring. His ceaseless sneezing made him exhausted and there were days he could barely see out of his swollen eyes. After a number of holistic treatments, we finally resorted to Claritin, and even that didn't kick in for a while. A few months ago, I posted this blog about the findings from Dr. Martin Blaser and his team. Through a number of studies, he has shown that the increase in many of our chronic illnesses today, including hay fever and asthma, are directly linked to a change in our microbiomes. It's fascinating stuff.

Thomas Leo Ogren has another equally fascinating theory that may likely piggy-back on the microbiome changes.

Author of The Allergy-Fighting Garden, Ogren is a horticulturist and allergy researcher. In his previous lifetime, he owned a nursery, instructed landscapers, and hosted his own radio garden show.

If you care anything about gardening, you should get this book. If you care anything about keeping your home as allergy-free as possible, you should get this book. Ogren has given nearly 3,000 plants an allergy ranking.

So here's the deal behind Ogren's theory...

Once upon a time, there were male and female plants. Well, not all of them were male AND female but I will get to that later.

These male and female plants co-habitated nicely. The male plants released their pollen when it was time and the females took that pollen in, eventually creating little seed pods which maybe turned into seedlings.

Then the 1950's happened, that period of time where identical square patches of chemical-laden green lawns sprouted up in every suburban neighborhood across the country. City planners decided that female plants, with all their seeds and fruits, were too messy. So let's get rid of them and only use male plants, was the thinking. Our sidewalks will be nice and neat.

Free from seed pods the sidewalks became, but over the years another kind of nuisance happened.


Lots of it.

Why? Because male plants produce all the pollen and without females there to gather it all up, it stays in the air. It lands on the sidewalks. It enters our cars and our work places and our homes.


Ogren explains that a typical pollen grain is about 20 micrometers (a human hair is about 75 micrometers across), small enough to pass through even the tightest window screen. He placed pollen on a slide and then part of a window screen over it. (See photo.) After seeing the results, Ogren estimates that a thousand grains of pollen could simultaneously pass through each tiny square in the screen. Wild.

So I HAD to ask him questions, and Ogren was great enough to take the time to answer...

I was glad to have read through your book before planting the lilac bush right outside my kitchen window. I had no idea it was a plant that many are allergic to! Are there other top allergen plants that people tend to plant too close to their homes?

I would never recommend planting any male trees/shrubs close to a window. In particular no male junipers or yews near windows, also no male Podocarpus near windows. Lilac is an example of one that the smell can trigger allergies, so would not use this near a window, nor would I use Jasmine next to a window. Plants with poisonous pollen, such as rhododendron, should also not be planted right next to windows. Profuse blooming climbers such as some of the vigorous types of clematis are not good near windows. Cypress of any kind are not good next to windows. Mountain Laurel (Kalmia latifolia) has very toxic pollen and should never go near a window.

In your book, you offer some great tips about how to identify male from female plants. The most obvious seems to be that a male tree or bush will never have fruit, or pods, or seeds of any kind. Will most landscapers or nursery workers know the difference if we ask?

No, alas, most landscapers or nursery workers will not know the difference between a male of female plant…we need to educate them on this, soon.

I hope you do! I am blown away by how comprehensive your book is. It should definitely be on the shelf of any family living with hay fever and even food allergies (as plants like lupine can be an allergen to those with peanut allergies). Examples are you rate many of the morning glories with a 4, which means they are about medium in terms of causing allergies, while impatiens get a recommended rating of 1.

How did you develop your OPALS (Ogren Plant Allergy Scale) rating system?

It started to get very complicated when I’d explain to non-botanical, non-horticultural trained people why one plant was good, nor not. I decided I needed a scale, a numerical scale that would simplify it all. I asked two questions for starters: A. What does this plant in question have in common with other plants that are well known to cause allergies? B. Then I asked the flip side question, what does this plant have in common with plants known not to cause allergies? I used these two questions as the starter blocks.Eventually I developed a large set of criteria, questions, per allergies, and applied them against each plant to be ranked.

Examples: how long does it bloom? How potent is each grain of its pollen? Are the stamens hidden or exerted? What is the ratio of male to female parts in each flower? Does the plant trigger odor challenges, or skin rash/itch issues? How large is each pollen grain? What is the shape of the pollen grains? Is the specific gravity of each pollen grain light, or medium, or heavy? Is there a cross-reactive response with different common foods? And so on….I have more than 140 possible ranking criteria that I now use to end up with an accurate OPALS® number.

That's amazing. So as I understand, some plants are dioecious, which means there are female organs on one plant and male on another. Other plants are monoecious, which means they carry both organs. Is it safe to say that most monoecious plants are going to be pollen-producers and therefore more allergenic?

All monoecious plants will be far more allergenic than a dioecious female plant….and, almost all monoecious plants will also be more allergenic than a perfect-flowered plant….however, there are some exceptions. In general, being monoecious is a sign of allergy-potential, because monoecious plants will produce all-male flowers, and these are almost always problematic to some degree. A monoecious plant with a good balance between male and female flowers…(such as a fibrous begonia} are much less allergenic…nonetheless, most monoecious plants have far more male than female flowers.

You were invited to present your arguments to those in charge of city landscapes in New York City, but those in charge dismissed your arguments, saying that most trees only produce pollen a few days of the year, at most. My little guy was sneezing for weeks this spring. I can't believe that was an accurate argument.

It wasn’t even close to being accurate! Most deciduous trees produce pollen for weeks, and often for months. All the pollen is not released at once and pollen release is often sporadic, depending on the changing weather. ALSO, pollen falls out close to a tree and then wind can pick it up and move it around….fallen pollen can remain highly allergenic for months.

In the past few years, there have been laws created in big cities like Albuquerque and Las Vegas, as well as Edmonton and Toronto in Canada in order to reduce the amount of trees that trigger allergies. Do you see this as a trend that will continue? Are people becoming more educated and receptive?

Yes, this is the start of a trend to use more allergy-friendly trees/shrubs. Allergies and asthma make city life much less pleasant, they result in huge costs to society in missed work, missed school, in unproductive work, unproductive studies, in costs for hospitals, doctors and medications. One would think that eventually cities and certainly insurance companies would want nothing but allergy-fighting, allergy-friendly landscaping, certainly at all schools, public parks, etc.

Tom, this book clearly took a great deal of time and effort. What was your motivation for starting this comprehensive project?

My motivation for this huge and very long and time-consuming project was my wife, Yvonne. She has terrible allergies & asthma. I've always noticed that her asthma attacks came just when her allergies were out of control. I wanted to re-landscape our own home so that nothing in our own yards would trigger her allergies. This was my motivation, and for almost a decade now (knock on wood!) she's been free from any asthma attacks.

Wow. That is truly amazing and empowering! As somebody who grew up with severe hay fever and asthma, I know what a relief Yvonne must be feeling. How wonderful that we all benefit from the love you have for her.

Thank you so much for your time!