Hay fever plants and Weather

Plant species producing allergenic pollen

Click on thumbnail for a zoom

Images: J. Derksen
Hay fever is only provoked by airborne pollen, sometimes by amphiphilous species (in with pollination occurs by the wind, as well as by insects). It is a luck that only little types ofpollen are allergenic among entomophilous plants (with wind pollination) which produce large amounts of airborn pollen (see tables here below about allergenic pollen). The risk to be in contact with pollen transfered by insects (entomophilous), like that of most garden plants with colorful flowers, is low, and besides this pollen is known to be little allergenic. Some species which in first instance are suspicious because they release remarkable amounts of pollen in the air do not (or seldomly) cause hay fever (Examples: the Ash, Aspen and Taxus, resp. Fraxinus excelsior, Populus sp. and Taxus baccata, see video presentations of the Ash, Aspen and Taxus, and illustrated descriptions of Ashes, Aspens, Taxus species and a SEM photo of Taxus pollen). Although this is the general tendency, some people are yet sensitive to pollen that is known as little or not allergenic. And opposite, the great majority of the population does not suffer of hay fever.

In the Netherlands and Belgium the pollen of the following plant species is most responsible for hay fever symptoms (upper table, groups arranged according to their allergenicity / importance; lower table with links to video's, descriptions and scanning electron microscopy photo's of the plants. Take care, realize that this list is not complete and take into account individual differences in specific sensitivity and (cross-)reactions). In South-European countries, in top of the grasses, Pellitory-of-the-wall, Eastern Pellitory-of-the-wall and Olive are the main source of hayfever pollen (see video "Vakantiepollen" showing these plants in details on pollennieuws).
 

The weather

[eng] The weather is a main factor for the formation and dispersal of pollen. Temperature, air humidity and precipitation not only have a great influence on the flowering time of plants, but also on the duration of the blooming and on the amount of flowers and pollen which are produced. For hay fever patients dry and sunny weather is most unfavorable, because then the anthers disrupt and pollen is shed in mass. If in addition the wind is blowing, pollen can be dispersed over long distances. This is not the case with rain weather which also helps to wash much pollen away. The weather forecast is an important consideration in making hayfever predictions (to the site of the KNMI)
 
Main sources of hayfever in the Netherlands and Belgium
Grasses (Grass family = Poaceae or Gramineae; e.g. Cockfoot pollen, one of the major source of hay fever (May-fall).
Birches (i.e. the Silver and the Downy Birch, which flower in spring. Photo: Birch pollen
Mugwort which flowers in summer. Photo: Mugwort pollen
Alders, e.g. the Common and the Grey Alder, causing both hay fever already in wintertime. Photo: Alder pollen
Hazel, which flowers early in the year. Photo: Hazel pollen
Plantains, which flower from May to September. Photo: Ribwort Plantain pollen
Sorrels (Dock species) which flower most in May and June, but even until October. Photo: Sorrel pollen
Level of allergenicity and occurance of disconfort from
low / seldom (0-1) to
high / common (4-5)
 

Note 1: Allergenicity = how seriously causing hayfever)
Note 2: Alders and Hazels belong both to the Birch family or betulaceae. Most people become allergic for Alders and Hazels pollen only when they are already allergic for Birch pollen. This is also valid for Oak pollen. More about cross-reactions at natuurkalender.nl
Note 2: In southern countries hayfeverisalsocaused by other plants like olive trees and cypresses.

 
Click in the table here below on the arrows ↑ ↓ to sort according to the alphabetical order, level of allergenicity or month
Plant species with allergenic pollen
Scientific
name

 
 
Alphabetically ↑ ↓
English
name

 
 Alphabetically ↑ ↓
Allergenicity
0-5

 
Sort ↑ ↓
Flowering
month(es)

 
Sort ↑ ↓
Tree/
Bush

Grass
Weed

Sort ↑ ↓
Video (1)
Flora (2)
(Links)
SEM (3)
 
 
 
Alnus glutinosa
Alnus incana
Common Alder
Gray Alder
02-03-04 Tree/
Bush

Wild plants
SEM photograph of Common Alder pollen
Alopecurus pratensis Meadow Foxtail 04-05-06-08-09 Grass
Wild plants
 
Ambrosia sp. Ragweed 08-09-10 Weed
Wild plants
SEM photograph of Ragweed pollen
Anthoxatum odoratum Sweet Vernal Grass 04-05-06 Grass
Wild plants
 
Arrhenatherum elatius False Oat-grass 05-06-07-08-09
Grass
Wild plants
 
Artemisia vulgaris Mugwort 06-07-08-09 Weed
Wild plants
SEM photograph of Mugwort pollen
Betula sp. Birch 04-05 Tree/
Bush

Wild plants
SEM photograph of Silver Birch pollen
Bromus hordeaceus Soft Brome 05-06-07 Grass
Wild plants
 
Carpinus betulus Hornbeam
04-05 Tree/
Bush

Wild plants
 
Cedrus sp. Cedar 08 Tree/
Bush

Wiki
SEM photograph of Lebanon Cedar pollen
Corylus avellana Hazel 01-02-03-04 Tree/
Bush

Wild plants
SEM photograph of Hazel pollen
Cynosurus cristatus Crested dog's-tail 06-07-08-09-10 Grass
Wild plants
 
Dactylus glomerata Cocksfoot 04-05-06-07
Grass
Wild plants
 
Elytrigia repens Quackgrass 06-07-08 Grass
Wild plants
 
Holcus lanatus Yorkshire-fog 05-06-07-08 Grass
Wild plants
 
Holcus mollis Creeping Soft Grass 06-07-08 Grass
Wild plants
 
Lolium multiflorum Italian Rye Grass 06-07-08-09-10 Gras
Wild plants
 
Lolium perenne Perennial Ryegrass 06-07-08-09 Grass
Wild plants
 
Parietaria judaicaPellitory-of-the-wall 05-06-07-08-09-10 Weed
Wild plants
 
Parietaria officinalisEastern Pellitory-of-the-wall 06-07-08-09-10 Weed
Wild plants
 
Phleum sp. Timothy 06-07-08 Grass
Wild plants
 
Plantago lanceolata Ribwort Plantain 05-06-07-08-09 Weed
Wild plants
SEM photograph of Ribwort Plantain pollen
Poa annua Annual Meadow-grass 04-05-06-07-08-09-10 Grass
Wild plants
 
Poa pratensis Smooth Meadow-grass 05-06-07 Grass
Wild plants
 
Quercus robur
Quercus petraea
Pedunculate and Sessile Oak

variable
04-05 Tree/
Bush

Sessile Oak
Pedunculate Oak
wilde-planten.nl
 
Rumex acetosa
Rumex acetosella
Rumex crispus
Rumex obtusifolius
Common Sorrel
Sheep's Sorrel
Curly Dock
Broad-leaved Dock
05-06 Weed
Common Sorrel
Sheep's Sorrel
Curly Dock
Broad-leaved Dock
SEM photograph of Sheep's Sorrel pollen
Salix viminalis Basket Willow
03-04 Tree/
Bush

Wild plants
SEM photograph of White Willow pollen
Secale cereale Rye 05-06 Grass
Wiki
 
Tilia sp. Lime/Basswood
(Small-leaved, Large-leaved and European Lime)

06-07 Tree/
Bush

Wild plants
SEM photograph of European Lime pollen
Urtica dioica Stinging Nettel 06-07-08-09-10 Weed
Wild plants
 
Zea mays Maize 07-08 Grass
Wiki
SEM photograph of Maize pollen
  • (1)Video presentations: Video's (in Dutch) from Pollennieuws.nl ©, with information on hay fever prognosis, the pollen plant of the week and pollen.
  • (2)Flora: links to Wilde-planten.nl (in Dutch) or subsites of Wikipedia (in English). Wilde-planten.nl hosts a searchable database in which about 1800 wilde plants from Belgium and the Netherlands are described (the properties, biotope and occurance of each species) and pictures are shown of the habitus, flower, seeds and more.
  • (3)SEM: photographs (©) of pollen grains from the collection of Dr. J. Derksen (Radboud University Nijmegen) who has allowed viewing of this material through the present site.

 

Literature/references

  • Derksen, J., Wissen, H. van en Marijnissen, J. 2007. Pollen en hooikoorts. Tirion, Baarn. ISBN : 9789052106670. 126 pp.
  • Wodehouse, Roger P. 2007. Hayfever Plants. READ BOOKS, ISBN 140676678X, 9781406766783, 272 pp. (About the area of the USA)
     
    Webpages and SEM photographs:Jan Derksen and Elisabeth Pierson
    Thumbnail of plants: Ben Goossens (original photo's on pollennieuws.nl used with permission)
    Web development: Remco Aalbers
  • http://www.vcbio.science.ru.nl/en/virtuallessons/pollenplants/print/

    last modified: 1 Oct 2013