Articles of Interest - 2018

[By clicking on an item below you will be taken to a page containing that article]




Brave new world...of non-allergenic parks in Hamilton  [December 9, 2018]


Plants for Clearning the Air  [November 12, 2018]


Children's Right to Play and Recreation in Urban Areas  [October 15, 2018]


Not all plants trigger allergies  [May 15, 2018]


'Pollen bomb' video shows that the male species is responsible for your allergies  [May 11, 2018]


Allergy season is getting longer in parts of Canada.  Blame climate change, experts say  [May 6, 2018]


Guernsey resident celebrated at our Allergy Heroes Awards  [May 4, 2018]


We calculated how much money trees save for your city  [April 27, 2018]


Pollen-allergy researcher Tom Ogren talks allergy friendly gardening  [April 24, 2018]


Tokyo struggles with worst hay fever outbreak on record  [April 23, 2018]


'Pollen bomb" brings misery after joy of warm weather  [April 22, 2018]


How to Keep Allergens Out of Your Garden with Expert Thomas Ogren  [April 11, 2018]


In sniffling Islamabad, pollen allergies soar as spring brings less rain   [April 9, 2018]


Antibiotics and antacids linked to allergies in kids   [April 6, 2018]


the Morning Blaze with Doc Thompson (Hour 1)  [April 5, 2018)


'BOTANICAL SEXISM'?  Scientist blames allergies on 'male-dominated' tree planting   [April 5, 2018]  


Tips for making your home a pollen-free zone   [April 3, 2018]


Botanical sexism with trees making seasonal allergies worse   [April 3, 2018]


Plants for health   [March 2018]


NICH Releases The Power of Plants: Enriching Lives, Creating Jobs, Building Wealth, Saving Money  [March 30, 2018]


Is 'botanical sexism' making allergies worse?   [March 29, 2018]


CDA Plans to Remove Paper Mulberry Trees   [March 29 2018]


Be Aware of Pollen!  Allergenic Plants   [March 16, 2018]


Tom Ogren on Trees in the Built Environment    [March 12, 2018]


Not to be sniffed at    [March 2018]


Impact of Cleaning Products on Women's Lungs as Damaging as 20-A-Day Cigarette Habit: Study   [February 18, 2018] 


Want Cleaner Air?  Try Using Less Deodorant   [February 16, 2018]


Opinion: Here's a Way You Probably Haven't Thought of to Reduce Allergies and Asthma   [February 13, 2108]


Trees make you healthier, but choose wisely   [January 10, 2018]




For articles in 2017 please click on one of the following:  2017           


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Children's Right to Play and Recreation in Urban Areas

October 15, 2018
INFO: Arbor day is the last Friday in April in both Canada and the USA.
Maple Leaf day (only in Canada) falls on the last Wednesday in September, during National Forest Week.

Children's Right to Play and Recreation in Urban Areas
From: Peter Prakke

What better day, than Arbor Day, to bring the spotlight on children and trees? The advantages to children, from being outdoors, are many as they get fresh air and exercise, as well as nurturing a sense of wonder about the environment around them. Often, however, this outdoor experience is not pleasant and in some cases even not possible, due to allergies and asthma.

On Arbor Day it is tradition for the community leadership, the Mayor, to plant a tree with the children of a local school.

What I propose is that, in line with the Child's Right to Play and Recreation, under UNICEF's Convention on the Rights of the Child, Mayors select allergy-friendly trees, according to the OPALS® scale. In this way, we ensure that the trees, and the areas in which they are planted, are able to be enjoyed by the broadest number of constituents of all ages.

OPALS® is the plant allergy scale that measures the allergen potential of all landscaping plants, based on a numeric scale where 1 = allergy friendly and 10 = high allergen potential and to be avoided, with the goal of promoting the health of children and the general population. Allergy-friendly trees are often the female of the tree species, which collects pollen resulting in cleaner air and which has the added benefit of providing for the food-chain through seeds and fruits. The pollen-producing male trees are more likely to trigger asthmatic and allergic reactions to their pollen. The effects of high pollen counts are most common in urban areas, where not only are there fewer female trees to capture the pollen, but the abundance of concrete and asphalt serve to preserve and circulate the pollen across larger areas, negatively impacting larger numbers of people.

To expand the number of areas where people can engage comfortably with nature, and recognising that it is also common for community service organisations to plant trees in a designated park or urban area on Arbor Day, I would suggest that schools use the annual opportunity to plant at least one allergy-friendly tree. Community-based organisations such as Rotary, Lions, 4H, Boy/Girl Scouts, as well as religious centers and horticultural societies are others who could be encouraged to procure and plant at least one or two allergy friendly trees in designated locations.

In this way, pollen is increasingly kept under control and more people are ultimately able to enjoy time in nature.


Articles of Interest - 2017

[By clicking on an item below you will be taken to a page containing that article]



City to have first-ever pollen count station  [December 11, 2017]

Line streets with trees to reduce number of asthma attacks, experts say   [November 17, 2017]

Line streets with trees to prevent serious asthma attacks, say scientists   [November 17, 2017]

Pollution is the largest health inequality in Europe - New Lancet's report   [November 9, 2017]

Victoria considers gardening changes to help allergy sufferers   [November 8, 2017]

Low allergen gardening   [October 27, 2017]

Commemorating Fallen soldiers with Bravery Parks   [October 24, 2017]

"Allergy-Free Tree Selection"  A Seminar led by Tom Ogren at Barcham Trees    [October 19, 2017]

10 Books That Shine a Light on Allergies   [October 10, 2017]

Planting an Allergy-Friendly Future   [August 29, 2017]  

What's killing trees during droughts?  Scientists have new answers.   [August 7, 2017]

The challenging art of pollen forecasting   [July 20, 2017]

How to Make an Allergy-Friendly Garden   [June 28, 2017]

Importance of the Allergy Friendly Landscape  [June 14, 2017]

Sustainable Design of Green Zones  [May 31, 2017]

Toward an Allergy-friendly Australia   [May 2nd and 3rd, 2017]

'Botanical sexism' makes life worse for allergy suffers   [April 27, 2017]

The Troubling Link Between Springtime Allergies and Suicide   [April 21, 2017]

Why can't I play in our schoolyard?  [March 28, 2017]

Twenty-two Tips for Producing Low-Allergy Gardens  [March 7, 2017]

Far Higher Death Rate Among Black Children with Asthmna in U.S.  [March 2017]

Create a Sneeze-Free Garden   (February 21, 2017)

10 Things to Never Say to Someone With Food Allergies  [2/21/17]

Building greener cities: nine benefits of urban trees  [January 31, 2017]

When pollen attacks!  Experts reveal new approaches to combating hay fever  [January 21, 2017]

Building the asthma-friendly school garden  [January 1, 2017]  


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Allergy Free Tree Selection


"Allergy-Free Tree Selection"

A Seminar led by Tom Ogren at Barcham Trees, 19 October 2017

Report by Colin Hambidge          


Barcham Trees secured another great 'catch' for its series of arboricultural seminars when it lured Tom Ogren from California to present a seminar at its Cambridgeshire nursery. He is one of the leading experts in the field of allergenic plants and their impact on people and communities. He devised the OPALS® (Ogren Plant Allergy Scale) which is now used by, among others, the American Lung Association and the USDA Urban Foresters.


The scale measures the allergy potential of all garden and landscape plants within a range of one to ten; the higher a plant's rating the higher its risk of being an allergen. For example, Acer rubrum Autumn Glory is rated at one, while Callistemon citrinus (bottlebrush) is rated at nine. More than 130 different criteria are used to develop allergy rankings for plants. Each factor is either positive or negative. All factors are not weighted the same because some are more important than others. Most plants will have a combination of positive and negative factors that are computed to determine their OPALS® ranking. 

Some of the factors used to rank a plant include the amount of pollen produced, the potency of individual pollen grains, length of flowering, the size, density, shape and weight of the pollen grains, sex if dioecious, average rankings in actual skin scratch, patch and sniff tests, and cross-reactivity to food allergies. Additional information regarding the factors used to build OPALS® may be found in Tom's book Safe Sex in the Garden.


 Tom Ogren's main objective now is to help drive a robust, healthy trend toward allergy- and asthma-friendly gardens and landscapes in urban areas. For 30 years he has been researching the connections between the planted urban landscape and human health, in particular pollen-allergies and asthma. He has published three books on this subject, the latest being The Allergy-Fighting Garden.


His interest in the subject began around 30 years ago when his wife, to whom he has been married for 50 years, developed asthma and allergies. At the time, Tom read a book which claimed allergies were actually psychosomatic; this was a theory he was happy to accept at the time, but as his wife's problems increased he grew to realise the theory was not true. "Allergies affect how we perform in our lives and can have major negative impacts on us", says Tom.


Dioecious plants - those which are either wholly male or wholly female - are of particular interest to him. Dioecious trees include willow, red maple, holly, yew, juniper, mulberry and bay. While urban trees, and especially those in public areas, are predominantly male and therefore shed no fruit onto pavements, female trees produce no pollen and so may be termed 'allergy-free' or 'allergen-friendly'.


Tom Ogren is a great advocate (one might almost say 'evangelist') of female trees and of female plants in general. He is an avid plant collector and claims to have the largest collection in the world of female cultivars of trees, shrubs, vines and grasses that are useful in landscapes because they are totally pollen-free. He is also a consultant to states, cities, counties, schools, hospitals, and has worked for pharmaceutical companies.


He lectures frequently to healthcare professionals, city planners, arborists, landscapers and nurserymen, and now has several partners in a commercial venture to get many more pollen-free plants available to the public.


So how big is the problem of allergies? Tom told us that in 1950, it was thought that two to five per cent of the population of the USA had pollen allergies. This figure had grown to 12 per cent in 1988 and had rocketed to 38 per cent by 1999. Asthma is the most common chronic illness of childhood in the USA, and developing pollen allergies more than doubles the chance of a child developing asthma.


In 2017 the charity Asthma UK ( reported there are currently 1.1 million children (1 in 11) and 4.3 million adults (1 in 12) receiving treatment for asthma. The condition also increases the risk of developing heart disease and leukaemia, while women who have airborne allergies are at an increased risk of ovarian and breast cancers (Cell Biology, 2010 Study). Tom also mentioned more women than men suffer from asthma.


Another charity, Allergy UK (, reports that 44 per cent of adults in Britain suffer from at least one allergy, and the number of sufferers is on the rise, growing by around two million between 2008 and 2009 alone. Almost half (48 per cent) of sufferers have more than one allergy (Mintel, 2010).


While pollen is capable of travelling considerable distances, Tom told delegates most lands very close to where it originated. For twelve years, he taught landscape gardening in a California Youth Authority maximum-security prison, and he has also worked with the University of California Cooperative Extension, to establish community gardens in the Los Angeles inner city. While he is an advocate of using female plants in landscapes and gardens, he does not feel they should be used to the exclusion of male and monoecious plants (those which have both sexual reproductive systems on the same plant). "All plants are useful - in the right place", he says. ""I would now never plant pollen-producing plants near doors, windows or too close to any part of a dwelling, but they can still be grown elsewhere".


It disappoints Tom that so many landscape and garden designers limit themselves to around only 12 different plants, which they use in most of their projects. "It's boring, and I much prefer plenty of diversity in planting schemes. Diversity of planting acts as a safety net or insurance policy".


He then went on to discuss plant cross-reactivity, with birch being used as a good example. Birch allergens have been found to cross-react with alder, hornbeam, hazel and sweet chestnut. Scientists in Sweden have also discovered that some trees cross-react not only with other trees, but also with certain foods. Again, birch can cross-react with apple, celery, carrot, cherry, potato and walnut, and many others.. Tom explained most allergens are proteins and that because birch pollen and apples have similarly shaped proteins some people may be allergic to both.


Tom Ogren is certainly a larger-than-life character, an excellent and entertaining speaker, and is also a man with a serious, but very simple message. I found it particularly interesting to hear that while his work has received acceptance from medical professionals and allergists, nurseries are much more wary of what he has to say. Now why could that be?


Contact details:

Thomas Leo Ogren Websites:



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