Creating Low-Allergen Gardens

While the gardening industry enthusiastically extols the healthful benefits of gardening, spare a thought for the many sufferers from hayfever and asthma whose gardens may actually be a health hazard.

For this reason, overseas allergy specialists and organisations are urging landscapers and nurserymen to come up with low-allergen design concepts. These mainly involve the use of plants that do not produce pollen that sends asthma and hayfever sufferers reaching for their anti-histamines. In Australia and New Zealand approximately 19% of adults, 15% of teenagers and 20% of children have asthma, while 20% of the population of these two countries suffer from hayfever, which though less dangerous is still extremely distressing. Much of this can be attributed to pollen. The main offender is grass pollen, particularly from exotic species, and includes many lawn grasses. Other problem plants include common garden trees, shrubs, herbaceous species and weeds. Some plants on the list that follow are notorious offenders, but others may only be a problem to those who are particularly susceptible. Some people are highly susceptible to a wide range of plants. The list that follows contain only plants proven allergenic to a significant number of people. Of the trees and shrubs, certain species of Acacia, Albizia, alder, ash, birch, Callistemon, Casurina, Coprosma, Cupressus, pine, elm, Liquidamber, maple, Meluleuca, mulberry, plane, privet, oak, olive, poplar, willow and woodworm are common problems. Asters, chrysanthemums, marigold and chamomile are annuals and herbs that cause problems regularly. Other surprising offenders are spinach and sweetcorn.

Pollen related problems peak in spring when pollen released by wind-pollinating plants becomes airborne. It is these, rather than bird or insect pollinating plants, that are the main trouble makers. In warm, temperate areas there is usually a low level grass pollen count all year round. Although those allergic to pollen will of course be exposed to it in the environment, it is in the immediate environment - the home garden - which is usually the main source of everyday pollen allergies. It is therefore common sense to plant low-pollen producing plants and grasses. It is also advisable to have a "low maintenance" garden to minimise the time spent working in it: thus reducing the period of exposure.

Pollen is not the only cause in the garden of hayfever and asthma attacks. Other offenders include dust and mould spores, which means that composts, organic mulches and certain fertilisers must be avoided completely or handled with extreme care. For example, a mask could be worn over the mouth or nose. A low-allergen garden may also need to avoid those plants responsible for skin allergies. Regular possible causes of skin allergies are most Greyvilleas with pinnate leaves, Helichrysum, ivy, Philodendron, poinsettia, primula, polyanthus or primrose, Rhus succedanea (Poison oak) and most plants that have milky sap or are hairy. Sufferers should also create awareness at schools and the workplace so that offending plants can be removed or avoided.

The basic guidelines for a low-allergen garden can be summarised as follows:

• Select low allergen plants. Avoid wind-pollinated plants. Insect and bird pollinated plants are usually those with the most attractive flowers.
• Opt for hard surfaces (paving) or non-allergenic groundcovers instead of common lawn grasses. Our indigenous Kweek (Cynodon dactylon) and buffalo grass (Stenotaphrum secundatum) are grasses that produce a minimum amount of pollen.
• Screening trees, hedges or walls will help trap pollen blowing from outside the garden.
• Keeping the garden well watered during peak pollen periods will help to settle pollen. Thankfully our spring is quite moist and this helps to settle some of the pollen.
• Mowing of the lawn stirs up pollen and should be avoided by those who are regular sufferers of pollen related asthma. To douse the lawn the day before or immediately after with water may also stop pollen from becoming airborne and affecting those who are susceptible.

There is a move abroad for nurseries and botanical gardens to create greater awareness of problem plants. Special labels are put on high risk plants warning buyers of potential problems. Some nurseries label their plants if they are particularly suitable for the low-allergy garden and a portion of the proceeds of the sale of those plants goes towards education and research programmes aimed at asthma control.