Thursday, February 26, 2015

Creating an Allergy-Free Yard

Two of my grandchildren have severe allergies, both food and environmental. Their tests show that pollen and tree nuts are some (of several) environmental culprits, leading to flare-ups when they stay at Nana and Pappy's house. But what can we do apart from keeping them indoors? With this problem in mind, I was thrilled to be given the opportunity to review a new book by Thomas Ogren, The Allergy-Free Garden: Stop Asthma and Allergies With Smart Landscaping. Tom, an eminent horticulturist, whose wife has asthma and allergies, became interested in allergy-free gardening more than 25 years ago. His research, lectures and publications have gained worldwide acclaim. I am ashamed to admit I never considered allergy-free landscaping before now. Tom's book, his fourth on this subject, was an eye-opener for me. I am totally in awe of Tom's important work.

I learned from the book that in the 1950's few people had severe allergies, but today asthma is the #1 chronic disease in children in the U.S. Tom explains how we created the problem -- yes, it is man-made. Originally, landscapers used plants propagated by seed, so there were more-or-less equal numbers of male and female. New discoveries allowed growers to produce separate-sexed plants, so they could choose one or the other. As you know, my dear gardening friends, the male produces pollen, the female produces fruit. As the female plants are the messy ones, the USDA recommended only male trees should be planted in towns and cities to reduce the amount of litter on sidewalks. Therefore, less mess, but 10,000 times more pollen than when both male and female were planted. Making it worse, not only do female plants produce no pollen, they trap and remove pollen from the air. The problem was further exacerbated when the trees lost through Dutch Elm Disease were replaced with male trees.
"Pollen is the invisible litterer"
-- Thomas Ogren
Male trees produce no fruit for birds and small animals to eat, and they produce little or no nectar for butterflies, hummingbirds and bees: probably one of the reasons for the decline in butterflies and bees in our cities. Fortunately, we don't have to be so particular about smaller plants. Low allergy pollinator plants make small amounts of large, sticky, not very allergenic pollen. Mints and other pollen-free female plants are rich sources of nectar. 

Catmint Nepata has low amounts of pollen and high amounts of nectar.

 Tom suggests you evaluate your existing plants. He does a good job of explaining perfect (bisexual) flowers, monoecious (single sexed) and dioecious (unisexual), suggesting ways you can determine the sex of a plant, giving several examples of each. An earlier book of Tom's has the attention-grabbing title, Safe Sex. It's a great title now we know the link between the sex of the plant and its power to cause or prevent allergies.

Snapdragon Antirrhinum. Perfect flower that spreads v. little pollen.

In one section of the book, Tom discusses eliminating allergy-causing mold spores with such considerations as mulches, airflow, and sunlight. He advocates IPM and avoiding insecticides and fungicides ... in my case this is 'preaching to the choir.' As well as advice on home landscaping, Tom shows how we can fight allergies in neighborhoods and cities by writing letters and sending emails. He draws attention to the concern about pollen in our school yards. In addition, he points out that the push to 'plant more trees' has no regard for the allergy problem.

The most important part of the book for me is the A - Z listing of allergy-fighting plants. Tom has developed the Ogren Plant Allergy Scale or OPALS. This is a numerical scale ranking such factors as amount of pollen produced, potency of the pollen, how long in bloom, size of pollen grains, etc. It is a 1 - 10 scale with one being the least allergenic. Each plant is ranked against other plants of the same type (obviously, a tree with a high rank will be worse than a perennial with a high rank, because of size.) The A - Z plant list is very comprehensive with cross-references, so you can find a plant when you only know the common name.  I enjoyed looking up my trees, shrubs, and flowers to see how they rank. My snapdragon pictured above is a 1 on the OPALS scale; catmint is 2.

Catalpa: OPALS 6
Hydrangea macrophylla: OPALS 3
Hydrangea paniculata 'Pinky Winky': OPALS 5
Deciduous Viburnum: OPALS 3
My many hostas are 1 on the scale
Globe amaranth gomphrena globosa :OPALS 4
Foxglove Digitalis: OPALS 2
Daylily Hemerocallis: OPALS 6
Milkweed Asclepia: OPALS 3

I read that my Juglans, Black Walnut trees, rank high at 8 to 9. As well as pollen, their rotting husk odor triggers allergies. My grandchildren love to play in the walnut grove where we hung a swing from the largest tree. Oh, dear.

Eastern Black Walnut Juglans nigra: OPALS 8 - 9

Each A - Z plant description gives growing conditions and other information as well as its ranking. Finally, the book has an excellent glossary, recommended reading list, list of useful websites, a pollen calendar, and a USDA Plant Hardiness Zone Map.
Tom sent me a free iBook in return for an honest review. I have ordered a hard copy from Amazon, because I need to take the book with me for reference when I go to the garden center to make my new plant purchases. Some companies have started using OPALS labels, but many have not. I wont be chopping down all my black walnuts right now, but I don't want to add any more high allergens to my garden. Check out Tom's web page, Allergy-Free Gardening, for more information and for links to purchase the book from your favorite book seller.

As you can see, I found the subject extremely interesting. I'm very grateful that I had the opportunity to review this important book. I highly recommend it. I am linking this posting to Beth at Plant Postings: Lessons Learned. A very important lesson, indeed!

Happy, sneeze-free gardening,

Pamela x

Helleborus ranks 4

~~ I love reading your comments. I hope you leave one so I’ll know you visited! 
I look forward to visiting your blog in return.


  1. Pam this is a great post. I honestly would have never thought of allergy free gardening. Thank you.

  2. Poetic justice! Yet another argument against the 'it's messy take it away' school of gardening.
    I have chosen shrubs and trees for the birds, and hope that I have the 'for the birds' sex.
    We've been very grateful to get away from the crop spraying and agrochemicals. Crisp sea air and the Cape doctor (the prevailing Southeaster) are a revitalising change.
    So gardening for pollinators needs to add - plant female trees too - to the guidelines.

  3. PS will you add this post to Beth at Plantpostings Lessons Learned meme. You need a WIDE audience for this one.

  4. I suppose I shouldn't really be posting on Pam's blog here, since I did write the book The Allergy-Fighting Garden, but I just now read her review here, and it is so thoughtful and well explained that I simply had to weigh in!
    This new book seems to be getting a wider audience, and in particular allergists far and wide have been plugging it....great to see that.
    Anyhow, Pam's English Garden is a perfectly marvelous garden blog...and as a gardener myself, I've got to say I LOVE her photos. Pam is obviously a dedicated and talented gardener. Great gardens don't happen by accident.

    1. Thanks, Tom. I'm glad you like my review of your wonderful book. I am overwhelmed with your generous praise of my blog. I hope you visit often.

  5. What an interesting post. I wasn't aware of this research and am fascinated by Tom's book. I agree with Tom - your photos are fab.

    1. Welcome to my blog, Sarah. I'll pop over and visit yours.Thank you for your kind comment.

  6. Pam great review.....this is an interesting book and I look forward to reading it. I have had allergies to grasses, trees and who knows what else. But being out in the garden I find I have outgrown them and have little issues now.

  7. There was a time I suffered with hay fever, seems like the more I exposed myself to the problem the easier it became, or did that just come about with old age. Fantastic to have the author pick up on your interesting post.

  8. What an interesting post. I suffered terribly from allergies as a child and young adult, though they seemed to subside when I had children, I don't know why. Unfortunately, I've passed them on to Daniel, he has very bad reactions in summer when the pollen's about.

  9. Good post, Pam and a wonderful, informative book. More and more kids are getting allergies and science has been looking into why. It is best not to have an environment that causes allergy to kick up.

  10. Interesting topic. I'm careful about fragrances as well as pollen because of allergies around here. We can't really change the forest or fields, and I wouldn't want to, but at least we can keep it off of our doorstep.
    Our son has allergies and we recently tested him for the types, I thought it was strange that most of his worst ones were plants not at all common to our area. I guess that says something for low doses to boost immunity since the local pollens weren't much of a problem.

    1. You are right about fragrances, Frank. Tom discusses them in his book, too.

  11. I guess we can't change the woods and fields around us, but at least this idea can keep the culprits off our doorsteps! Great topic.

  12. Hi Pam,
    I'm glad I made it here to see this post. I have not been keeping up with blogging very well lately, partly because I am on FaceBook too often. Are you on there? We should find each other there, if so.

    Our grandsons have allergies, but it's mostly food they've been tested for so far. The 7 year old has EOE, and can only eat a few foods. Our daughter-in-law has to pack his lunch every day. I wonder how native plants would rate on the OPALS scale.

    Thanks for your comment on my Wildflower Wednesday post. While I liked my other computer, I sure am enjoying this one. I'm thankful they were able to copy all of my stuff over.

    Our snow is melted. I hope yours melts soon, and the warmer temps arrive. It was warmer today, and I think we are supposed to get some closer to normal temperatures this week, with highs in the 30s and 40s.

  13. Thanks for sharing this interesting information. Very good lesson!

  14. Pam-this looks like a very informative book, especially for people concerned with allergies and I like the easy rating guide. Thank you for the review. I will have to bookmark this and keep it in mind. Happy March!

  15. Thanks for sharing this information, Pam. I didn't realize there was an actual scale that ranks trees and plants for pollen levels. I suppose a high OPALS scale and a sensitivity to a certain plant would be an excellent reason to replace it. I'm surprised that Hellebores rank so high. But, as you say a large tree would have a larger pollen footprint than a small perennial. Thanks for joining in the meme with this excellent post!

  16. Woah, I am just blown away by this post! That makes sense that allergies might be caused by the planted street trees. My husband had terrible allergies when we lived down South, but thankful they are much better up here in the Northeast (though I have a mild allergy to something up here). What a great book!!

  17. Fascinating topic - I had no idea. I wonder if that information is used over here.