Birds, bugs and allergies

Tom Ogren is a landcape gardener and the author of Allergy-Free Gardening and Safe Sex in the Garden – see his own website at He explains how encouraging wild birds to visit your garden could not only give you endless pleasure but help moderate your mould allergies.

As I write this I can look out my window and see a busy house sparrow going from the birdfeeder, to the suet feeder, to the blossoms of the pineapple guava bush. The sparrow eats a few sunflower seeds, takes a few pecks from the suet, and then yanks on the sweet fleshy petals of the red and white guava flowers (Feijoa sellowiana).

Bees and other insects seldom visit the guava flowers and they are pollinated almost entirely by birds. As the bird yanks on a petal, the pollen is shaken from the stamens onto the pistil and fertilization takes place. I first noticed this with mocking birds, and then with hooded orioles. Today is the first time I’ve seen a sparrow doing this work. The sparrow may not know it but he (she?) is making sure that I’ll have a good crop of guavas this autumn.

Just yesterday I was speaking to a group of gardeners about my book, Safe Sex in the Garden. I mentioned how terribly common whitefly-infested hibiscus and rose of Sharon plants were becoming now in many large cities, especially those with the worst air pollution. The air pollution, largely from the exhaust of all those cars and trucks, stresses and weakens many landscape plants, and this leaves them vulnerable to attack from insect pests.

I explained that when insects such as whitefly, aphids, scale, or mealybugs feast on our ornamental plants, they secrete large amounts of a gooey, nutrient rich substance we euphemistically call ‘honeydew’. On this honeydew dry airborne black mould spores land, stick, germinate, and quickly start to grow. The mould flourishes as long as it has a continuing source of insect-supplied honeydew.

Among other things, the dark mould spores on the leaves cut down on the amount of sunlight the plant can receive, and thus further rob the plant of needed food from photosynthesis. As the mould grows and spreads it turns the infested leaves and stems a fuzzy white or a sooty looking black. The entire effect is one of dirtiness, as indeed it is. The mould quickly reproduces itself by releasing billions of microscopic airborne mould spores. These spores float in the air, we inhale them, and allergy and asthma are the result.

Today there is great interest in indoor toxic mould, and yet outside, in far too many of our gardens, there is another mould spore epidemic well under way.

I often write and speak about male plants in our gardens and male cloned street trees lining our city streets, and about all the allergenic pollen that these male clones produce. Often overlooked in this discussion is the effect of mould spores from our landscapes. Overlooked even more, is the contribution to our good health from small birds.

Yesterday after my talk, a lady told me that she always feeds the birds in her yard and has done so for many years. She said she feeds them crumbled up small bread crumbs and that some 25 to 30 birds await her every morning. She also said that her own hibiscus plants are thriving, full of flowers, and unlike those of her neighbours, are bug free. ‘I see the birds eating the whiteflies and aphids from the hibiscus,’ she said. ‘I know that they are what is keeping it so clean.’

She is completely correct in this assumption, too. I also have seen small birds picking clean an infested bush. One day several years ago, a friend and I sat in his kitchen and watched as a small flock of tiny grey bushtits alighted in the blue mallow shrub next to the window. We knew the bush was loaded with aphids because we’d just been talking about it. As we watched, the little birds jumped from branch to branch, eating aphids. A half hour later when we went outside, the entire bush was aphid free.

Sometimes you will read that seed-eating birds mostly just eat seeds, but this isn’t true at all. Almost all wild birds eat insects. I encourage you to feed the birds, to encourage wild birds in your yard. Not only may they pollinate your guava trees, but they will also help rid your garden of insect pests, all the while making the air you breathe fresher and cleaner.

Trees and shrubs that attract songbirds with food and shelter:

Crab apple trees
Amelanchier trees
Mountain ash
Female holly
Female yew
Fruiting viburnum
Female junipers
Hawthorn trees


You can find all of Tom's books on allergen-free gardening here on Amazon in the UK and here on Amazon in the US.


First published in 2009

Articles on allergen-free gardening


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