WHAT ARE POLLENS?
Pollen is a fine powder made up of microspores produced by male plants. Pollen carries the male reproductive cells of seed plants. Seed plants include both conifers (plants whose seeds grow inside cones) and flowering plants. Some species self-pollinate when the pollen moves from the male part of the plant (the stamen) to the female part of the plant (the pistil). Cross-pollination occurs when pollen travels to the pistils of other plants, either in the wind or with birds and insects that it sticks to when they land on plants to drink their nectar. The birds and insects travel from plant to plant, leaving pollen on them and pollinating them. This is how plants are fertilized and can reproduce.
Pollen, especially the lightweight kind found on wind pollinated plants, such as grass, that is easily dispersed by the wind, is an allergen that causes a specific type of allergy called hay fever.
WHERE DO POLLENS COME FROM?
Hay Fever sufferers are allergic to pollens present in the air. These come from wind – pollinated plants, by far the commonest are grasses, weeds and trees.
Although there are many species of grass only a relatively small number are common and prolific producers of pollen enough to give high pollen levels in the atmosphere. Rye grass, planted for grazing, produces less pollen than traditional meadow grasses such as Timothy grass, sweet vernal grass, cocksfoot and Yorkshire fog. With increasing set aside of agricultural land, the meadow grasses will again dominate causing likely rising of pollen counts.
Cross reactivity between different species of grass is high, so if you are allergic to one type it is highly likely you will react others. The grass pollen season generally runs from mid May to the end of July with a peak late June to early July. Pollen levels vary from day to day and also within day depending on environmental factors.
The major tree pollens are hazel, plane, oak, ash and birch. These are produced in spring soon after the leaves develop. The major tree pollens are present for about 4 to 6 weeks late March to early May.
The weed pollen season is in the late summer in to early autumn and is the least significant of the pollen groups in the UK. In the southern parts of Europe, wall pellitory is a major problem and is now getting established here
POLLEN CALENDAR FOR THE UK