By Dr David Fountain
As I write this, pine pollen is everywhere – dust on car bonnets, yellow rings around puddles, and visible clouds of yellow dust when branches of pine trees are shaken. But by the time you read this, it is likely to be over because the pine pollen season is short and severe.
The annual release of this mildly allergenic pollen into the Aotearoa New Zealand air is in late winter. It marks the arrival of a large cloud of pine pollen that is shed from flowering pine trees over a two to four week period each year. Pine trees shed pollen from the small yellow male cones near the tips of branches.
Pinus radiata male cones shedding pollen visible as yellow dust
The chances of individual pollen grains (which are male) reaching the gaps between scales of the woody female pine cones are low, which is why so much is shed into the wind. The female cones eventually produce seeds and we collect the dry cones as fire-starters.
The appearance of pine pollen traditionally marks the start of hayfever season. I have some start times from the 2021 pollen season, as it usually follows a north to south sequence. It started in the north (including Auckland) around 15 July, followed by the Central North Island on 24 July, and finally Canterbury from mid-August. The pine pollen grains are about five times larger in size than other tree or grass allergenic pollens, but float in the air due to two gas bladders that enclose the cells that will cause fertilisation.
Electron micrograph of pine pollen showing 2 large gas bladders. The bar is 10 micrometres (0.01mm).
We can distinguish the pollen by the yellow dust particles and visible clouds formed when the cones are tapped. If you are in any doubt about how much pollen is released from a single pine tree, just watch the massive shower when a tree is bumped by a tractor, here: https://www.mirror.co.uk/science/huge-cloud-pollen-erupts-tree-18292275.amp
So, how much pollen is released in Aotearoa New Zealand each year? Well, the scale is huge. Some calculations can be made from data published by the New Zealand Forest Research Institute (https//www.scionresearch.com). A mature Pinus radiata tree can produce between 0.5 and 0.75kg of pollen each year. Typically, plantation forestry is 400 trees per hectare, so up to 300kg per ha per year may be produced. New Zealand has 1.6 million hectares of pine plantation forest, which equates to 500 million kg of pollen each year!
The way pollen travels is also very interesting. It is dependent on the wind when the pollen is shedding. Some of the pollen may be deposited near the source trees, but much of it will move a lot further. Massive yellow clouds have been reported to me over the years, as well as large mats of yellow scum floating in central North Island lakes adjacent to pine plantations. A pilot flying over plantations in the Waikato snapped a dramatic shot of pine pollen lifting out of the trees into the air below his plane.
Long-distance transport is a much-studied process for pollen dispersion and it depends strongly on the weather. Birch pollen in Scandinavia has been heavily studied, and travels many hundreds, even thousands of kilometres before settling out. Olive trees produce highly-allergenic pollen which also travels widely across Mediterranean countries. Grass pollen produced here in fields or on roadsides travels long distances as well.
For pine pollen, New Zealand is known for its ‘windiness’ from the west and south. We might assume that much of it is carried in the wind from plantation forests or from a single tree. These issues have not been studied but may be of ecological importance, since pollen is a natural nutrient-rich plant product.
However, we showed in the laboratory that pine pollen is much less nutrient-rich (as measured by protein content) than other pollens, especially when compared to grass pollen. This means that the ‘natural free fertiliser from the sky effect’ may not be quite so significant, but since the scale is huge, it undoubtedly is an unrecognised ‘input’ into land and ocean ecosystems.
Pine pollen, however does affect us. Some 20 per cent of New Zealanders have an allergy, and pollen allergy is a major component, usually classified as ‘seasonal inhalant allergy’. During the three or four weeks of pine pollen release, we are all breathing these pollen grains. Many people notice an effect on their health over this period - similar to a cold or the mild flu-like symptoms of a scratchy throat, irritated eyes and runny nose. This should not be confused with symptoms of viral infection by cold, flu or the COVID-19 virus, so proper diagnosis is required.
Reported common symptoms of exposure to pine pollen:
Scratchy sore throat
A wet cough with mucus in the nose, throat and sinuses
Slight upper respiratory wheezing
Stuffy or runny nose
Red, watery eyes when waking up
Often, this is non-specific irritation, but you should check with your general practitioner to investigate these symptoms further. Our work at Massey University showed pine pollen contains proteins shared by grass pollen, and that people who are sensitive to grass pollen react to pine pollen as well – a true allergy. This means a skin test or other immunological test using pine pollen extract will indicate if you are allergic to this pollen. You need to consult a medical practitioner to arrange this testing.
Dr David Fountain
Pollen Forecaster in association with Metservice NZ Ltd
Associate Professor, Plant Biology (Retired)
Massey University, Palmerston North
Aotearoa New Zealand
Cornford, C.A., D.W. Fountain and R.G. Burr. IgE-binding proteins from Pine (Pinus radiata D.Don) pollen: evidence for cross-reactivity with ryegrass (Lolium perenne) Int. Arch. Allergy Appl. Immunol 93: 41-46 1990.
Fountain, D.W., C.A. Cornford, G.J. Shaw and J. Allen. Pollen and allergy promotion. The Lancet 338:316 (l991)
Fountain, D.W. and C.A. Cornford. Aerobiology and allergenicity of Pinus radiata D.Don. in New Zealand. Grana 30 71-75 (1991).
Allergy Today, December 2021