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Piri Pollen Calendar

Welcome to the Piri Pollen Calendar where we help you to Act Before You React by showing you when the main allergenic plants are in flower.

Please note:
Timings will differ depending on where you are in the country. The exact timing and severity of the pollen seasons will differ from year to year depending on the weather and on biological factors.

Piri Pollen Calendar

What is Pollen?

The Pollen grain is the structure used to transport the male gamete (i.e. male DNA) to the female part of a flower. Pollen must be strong to protect the male gametes on their journey. The outer wall of the Pollen grain, called the exine, is composed of a very unusual substance called sporopollenin which is very tough. The inner layer is made of cellulose and is similar in construction to an ordinary plant cell wall. Pollen grains are microscopic - usually about 15 to 100 microns - and just a pinch of Pollen powder contains thousands and thousands of grains.

How can different Pollen types be recognised?

Each type of Pollen has its own unique set of characteristics which means that the species or plant family can usually be identified. In the case of grass Pollen, the different species are more recently evolved and their pollen grains are very similar to each other and so are usually only identified as grass in the count. The main features which distinguish one type of Pollen from another are size, shape and ornamentation of the outer wall.

Pollen grains come in a wide variety of shapes although the majority are basically spherical or oval or disc-shaped. The outer wall features include pores and furrows, e.g. grass has one pore and no furrows, birch has three pores and no furrows, oak has three furrows with a pore in the middle of each one. The surface of the grain can also have a meshed, granular, grooved, spined or striated surface or can appear very smooth.

Which Pollen types are most allergenic?

Most species of Pollen have some level of allergenicity but some are particularly notorious for inducing symptoms of hayfever. Grass Pollen affects about 95% of all hay fever sufferers and birch tree pollen affects about 20%. Oak tree, plane tree (common in many streets in London) and nettle Pollen are also well known for their allergenic properties.

One of the most allergenic species on an international level is the wind-pollinated ragweed . This is currently rare in the UK but is frequent in parts of the U.S.A., Canada and Europe. It produces a huge amount of pollen - up to 8,000 million Pollen grains can be released in just 5 hours from the giant ragweed species.

Wind-pollinated plants do tend to produce masses of Pollen to ensure that at least some of it reaches the right target. The majority of flowering plants are insect-pollinated and so their pollen does not need to be dispersed on the wind and they therefore produce smaller quantities of it. The pollen from these insect-pollinated species is often sticky to adhere to the bodies of insects and can form clumps, making it visible to the eye which often makes people assume that this is the Pollen type causing their symptoms. While such Pollen does have allergenic properties, the chances of it reaching the nose are usually slim.

So, it is the wind-pollinated species with their insignificant flowers (usually greeny-yellow and small) producing millions of Pollen grains that mainly cause the hay fever symptoms and trigger asthma in those susceptible.

Which Pollen types are most prevalent in the air stream?

In all, about 15 species that are known to be considerably allergenic are seen each year on the slides from the Pollen traps in the UK. There are about another five that are regularly seen but considered to be less of a problem. The traps also collect very small numbers of some other species, usually those flowering locally.

Overall, the traps collect only a very small proportion of the hundreds of different species of shrubs, weeds, grasses and trees that flower throughout the growing season in the UK, because, as mentioned above, most of them do not get airborne.

Most of the Pollen species that appear on the slides are Pollinated by the wind and are often produced in great quantity to ensure that at least some of the pollen reaches another flower of the same species. The air is also full of fungal spores at most times of the year.

Source: The National Pollen and Aerobiological Unit

What is the Pollen Count?

The Pollen count is a measure of the number of pollen grains of a certain type per cubic metre of air sampled, averaged over 24 hours. The Pollen forecasts are produced by the National Pollen and Aerobiology Research Unit using the pollen counts measured each day at the Pollen UK network sites, together with information about the weather, growing seasons and the flowering times of the plants.

Gardening with allergies

For those of us with seasonal allergies, getting out into the garden to enjoy the great British summer can be challenging. However, there are some steps you can take that can mean the difference between a pleasant spring, and a summer cooped up inside. The good news is that not all flowers produce offending pollen and with proper planning and preventative steps, allergies shouldn't have to keep you out of the garden.

Flowers, themselves, are not the enemy. The tiny pollen grains that flowers produce, however, are. After a long winter, plants, trees, and shrubs come alive, bloom, and produce the pollen that gets into our nose, sinuses, eyes and lungs.

Plants that pollinate using the wind are the worst. These plants send their pollen out into the world to find other plants. Unfortunately, they often find allergy sufferers.

Some flowers have a heavier pollen that is not spread by the wind, but instead is transported by the birds who are attracted to the flower's bright colour and nectar. These are the flowers that you should plant if you suffer from allergies because you are less likely to come into contact with their pollen.

Some perennials that are garden friendly for allergy sufferers are daffodils, crocus, hyacinths, iris, tulips, columbine, coral bells, peonies, and the ever popular day lily. Bougainvillea and azaleas are also on this list.

Annuals which have no history of causing allergies are impatiens, snapdragons, and petunias, geraniums, verbena, pansies, and zinnia.

Roses are some of the least offending flowers. Their pollen is large, and less likely to be spread around in the wind. Hybrid roses have even less pollen than wild roses and their varieties. When choosing a rose bush, the rule to obtain the least pollen is to choose the rose with the least smell. A pale pink Cecile Brunner rose and the Banksia rose produce no pollen whatsoever.

A couple of other pollen tips

  • Don't over water indoor plants. Soggy soil or water sitting in a drainage tray creates ideal conditions for mould growth.
  • When you work in the garden, protect yourself. Wear gloves, long sleeves, glasses (goggles, even) and a hat.
  • Wear a paper dust mask while mowing the lawn to reduce your exposure to pollens that are stirred up by the mower.

Source: The National Pollen and Aerobiological Unit - The University of Worcester