Pollen and grass

Trigger plants

A number of plants are associated with triggering asthma and hay fever symptoms in some people.

As a general rule wind-pollinated plants tend to be more problematic than plants pollinated by insects or birds, as their lighter, smaller pollen is more likely to become airborne and to be inhaled. Deciduous plants which release pollen from insignificant-looking flowers are in this category.

Commonly found "problem plants" in New Zealand include:


 Plants  Issue
Flowering   Period
 Pines Widespread - a major source of pollen Jul - Sep
 Oaks Produce a lot of pollen - some people very sensitive to it Aug - Oct
 Wattles Produce large quantities of pollen, though most settles near the plants
 Aug - Nov
 Birches Produce lots of pollen - some people very sensitive to it 
 Oct - Nov
 Grasses Widespread. Produce lots of pollen, which is carried long distances by the wind Oct - Feb
 Plantains Widepread; moderate pollen producers, but the pollen is strongly allergenic Oct - Feb
 Privets
 Produce lots of pollen, most of it settling on the ground within about 15m. Privet perfume an irritant for some people Oct - Mar


Olive trees have also recently been identified as an increasing problem as they become more widely grown here. Other shrubs and trees which are fairly common and can trigger symptoms in some people include alder, ash, coprosma, cypress, elm, liquidambar, maple, mulberry and plane trees.

Bird- and insect-pollinated plants with large, flamboyant flowers are less likely to trouble people with asthma and allergies. However, bear in mind that strongly scented plants can affect some people.

Flowers in the Asteraceae family can also be a trigger - these include daisies, marigolds, and chrysanthemums.

What can be done

Organisations such as schools and local authorities can help by avoiding common trigger plants in their grounds, gardens and hedges.

For individuals who are affected, the best solution is avoidance.

  • Remove any plants that trouble you from your garden.
  • Try to avoid going out on windy days.
  • Keep windows closed, particularly when out in the car. Some vehicles have air intake filters fitted, which help reduce the amount of pollen taken into the car.
  • See also the gardening tips below.

Other actions which may be helpful:

  • Use your asthma plan to help you adjust your medications as your asthma gets worse and better.
  • For hay fever symptoms, continue using your nasal spray if you have one.
  • Use pollen forecasts to help you gauge the likely risk of exposure to your triggers. At the time of producing this fact sheet, the MetService was issuing regularly updated pollen forecasts on its website - www.metservice.co.nz
  • Try to find out more about your allergic triggers with a skin prick test. (See our Asthma and allergy fact sheet for more information.)

Other gardening issues

Mould spores and dust, as well as "trigger plants", are a potential hazard in the garden.

Mowing, weeding and hedge-trimming can stir up pollen, dust and spores which are then inhaled at close quarters. If you are sensitive to any of these, have someone else mow your lawns and keep your hedges in shape, and stay inside while it's done. If you have to perform these tasks yourself, wear a mask which will help reduce exposure. (When purchasing masks, check for suitability and a secure fit, and ascertain how often they should be replaced.)

As a longer-term alternative, you may wish to consider replacing lawns with paving or plantings, and replacing hedges with fencing or trellis. Minimise your weeding with appropriate ground cover plants and mulches.

If mould spores are a trigger for your asthma, avoid organic mulches such as tree bark and manures, and use gravel mulch instead. As composting depends on moulds as well as bacteria, have someone else manage your compost. Also, exercise caution with potting mix - open bags slowly, and away from the face.

© Asthma and Respiratory Foundation of New Zealand (Inc.) 12/2001   Photocopy permission granted