allergy-free-gardening

I do so look forward to the signs of life in the garden after winter. When the first blooms of cherries, apricots and magnolias appear as harbingers of warmer days it brings a smile to my face. However, for people who suffer from allergies triggered by pollen, this can be the start of a miserable season of sore eyes and runny noses. For those with extreme reactions to airborne pollen, this is a time of flat out misery. Pollen can cause rashes, sinus conditions, headaches, fatigue, serious asthma attacks and an increase in COPD deaths.

Although a number of factors do contribute to allergies, pollen is the most common allergen to which we are exposed.  Even more worryingly, It has been discovered that traffic pollutants such as nitrogen dioxide and sulfur dioxide exacerbate pollen allergies.

Interestingly in the 1950’s only five percent of people in the UK were recorded as having pollen allergies. By 2010 this figure jumped to over 44% of the population and is now widely considered to be epidemic (Mintel, 2010). It is estimated that by 2025 half of the entire EU population will be affected! (https://www.allergyuk.org/information-and-advice/statistics)

What can account for this shocking increase in pollen allergy?

In the early years of horticulture, most landscape plants were propagated by seed, so male and female plants were about 50/50, as would naturally occur in the wild. With advancement in horticultural techniques, technology and chemicals, it became much easier and quicker to clone woody plants and allow growers to produce separate-sexed (male or female) plants of their choosing.

At this time, male plants and trees became preferable for public areas as they would result in litter-free plants, as male plants make no seeds, seedpods or fruit to fall on pathways and create a “mess”. What was not thought of however, was the fact the male trees and shrubs would all produce allergy-triggering pollen, and a great deal of it! The pollen production of a large male tree is ten thousand times greater than that of a tree with male and female parts (perfect-flowered).

Then in the 1960s and 70’s our native elm tree population was devastated by Dutch Elm Diesease (DED). At that time, elm trees had been a popular choice for both urban planting (Greenwich Park, Hyde Park and Kensington Gardens were all noted for their imposing rows of elm), and as boundary markers in farmland. Of the thousands of trees that died, many were replaced by these new “improved” cloned cultivars which were predominantly male. This ‘unnatural selection’ has left us with increasing levels of urban pollen as there are fewer and fewer female plants to absorb the pollen created by an ever-growing number of male trees and shrubs.

Many of the dioecious (single-sexed) cultivars of trees and shrubs you buy online or at garden centres are male clones. Some of the most common trees, shrubs and plants we buy produce high levels of allergy-causing pollen. Here are a few examples:

Italian-cypress-trees

Italian Cypress (Cupressus sempervirens)

Evergreens with short, needlelike leaves, often grey-green coloured. Not naturally a separate-sexed (dioecious) species, however modern horticulture has found a way to produce all-male trees. Highly allergenic and the cause of considerable allergy and asthma attacks.

Silver_Birch_Trees

Birch (Betula)

Extremely common landscaping tree, the ubiquitous Silver Birch (Betula pendula) a feature of many housing estates and parks. They shed a great deal of very allergic pollen but the blooming period is very short. An allergy to birch pollen may often also result in numerous food allergies.

salix-tree

Willow (Salix)

A large genus of more than 500 species worldwide. As separate-sexed plants, the female is actually an excellent addition to an allergy-free landscape or garden, however, male varieties are some of the worst allergy-causing trees.

bay-leaf-tree

Sweet Bay Leaf (Laurus Nobilis)

Used in pots to frame doorways or grown as bushes in gardens, the bay is a classic of the english garden. Males produce an abundance of allergy-causing pollen but females are pollen-free.

olive-tree

Olive (Olea europaea)

Appearing in ever-increasing numbers in modern urban gardens, olive trees are easy to transplant and many large trees have been moved from their original orchards into urban settings. Olive blossom is very light and easily spreads, thus a cause of severe allergy and a strong trigger for asthma. If olive trees are pruned hard each winter this does limit spring blooming.

Italian-cypress-trees

Italian Cypress (Cupressus sempervirens)

Evergreens with short, needlelike leaves, often grey-green coloured. Not naturally a separate-sexed (dioecious) species, however modern horticulture has found a way to produce all-male trees. Highly allergenic and the cause of considerable allergy and asthma attacks.

Silver_Birch_Trees

Birch (Betula)

Extremely common landscaping tree, the ubiquitous Silver Birch (Betula pendula) a feature of many housing estates and parks. They shed a great deal of very allergic pollen but the blooming period is very short. An allergy to birch pollen may often also result in numerous food allergies.

salix-tree

Willow (Salix)

A large genus of more than 500 species worldwide. As separate-sexed plants, the female is actually an excellent addition to an allergy-free landscape or garden, however, male varieties are some of the worst allergy-causing trees.

bay-leaf-tree

Sweet Bay Leaf (Laurus Nobilis)

Used in pots to frame doorways or grown as bushes in gardens, the bay is a classic of the english garden. Males produce an abundance of allergy-causing pollen but females are pollen-free.

olive-tree

Olive (Olea europaea)

Appearing in ever-increasing numbers in modern urban gardens, olive trees are easy to transplant and many large trees have been moved from their original orchards into urban settings. Olive blossom is very light and easily spreads, thus a cause of severe allergy and a strong trigger for asthma. If olive trees are pruned hard each winter this does limit spring blooming.

These, among many other common and popular plants can cause immense suffering to people with pollen-allergies and asthma.

How can I reduce the pollen in my garden?

Firstly, take a ‘garden-audit’ of the trees and shrubs you currently own and observe whether they bear fruit or seed of any kind throughout the year. Plants that do fruit or seed will either be female, so allergy-free, or contain both male and female flowers thus limiting the amount of pollen which is put into the atmosphere. Those plants which bear no fruit or seed will more than likely be male and further investigation will be needed into how much allergy-causing pollen they produce.

Once you have identified high-allergy plants, you can either look at moving them away from windows and doorways, perhaps to an area at the back of the garden or remove them entirely. In some cases you can top-graft male dioecious trees with scion wood from female trees to enact a sex change.

Finally, I can highly recommend Thomas Leo Ogren’s book “The Allergy-Fighting Garden” and anyone who is looking to reduce the pollen in their garden or aim to create an allergy-free garden should own a copy. Thomas Leo Ogen is the creator of the Ogren Plant Allergy Scale (OPALS), a plant allergy system which is now used by the United States Department of Agriculture. This book lists hundreds of plants, shrubs and trees along with an allergy scale of 1-10. A fantastic resource to plan your future planting.

I hope you find this article helpful in your quest to create an allergy-free garden.

Summary
Allergy-free gardens, a breath of fresh air.
Article Name
Allergy-free gardens, a breath of fresh air.
Description
Allergies from pollen have increased in the UK and Europe by nearly 50% in the past 60 years. Here I discuss some of the reasons for this increase in allergies and how to reduce pollen-producing plants in your garden.
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Publisher Name
Gaia Gardening Services
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