London, Ontario

Alder season can start from mid to late March and end late June. The counts fluctuate from low to moderate with an occasional high possible. The season is highly affected by the weather. They can be considered important allergens at these levesl.

Ash pollen season lasts well over a month. The season can start early to almost the end of April and end mid-May to early June. Some very high counts are observed and they are considered to be allergenic in highly sensitized individuals.

Beech season varies from year to year. Some years we get only sporadic and low counts and other years the season can last well over a month with low and moderate counts. This fluctuation is due to natural cycles and weather. The season can start from mid-April to early May and end mid-May to early June. May cause allergic reactions in individuals who are highly sensitized.

Birch season can start from the first to the last week of April and end mid-May to early June. The timing of the season varies from year to year as well as the amount of pollen produced. The pollen lavels can reach moderae or high levels depending on the year. They are considered important allergens.

 Cedars, junipers and yews produce low to high counts and the season varies a great deal from year to year. The season can start from early to late March and end late May to mid-June

Chestnut are important allergens and the season lasts from two to five weeks depending on the weather. The season can start from early to late May and end mid to late June. The Horse Chestnut, which is the most allergenic, is found in low to moderate numbers for approximately one to two weeks. The season can occur from mid-May to mid-June.

Elm are considered important allergens. The season can start early to mid-March and some years early April. The season end is from late April to early May. The timing of the season and the amount of pollen produced each year varies a great deal and this is partly due to the effect of weather. Mostly low to moderate counts are obtained. High counts can be observed some years.

Grasses season is from late April to October. Moderate and high counts are observed from May to late July.

Hickory have a short season which usually occurs late April and only has low counts. The main season can start early to the third week of May and end mid to late June. The pollen levels can vary from year to year and moderate counts can be observed. The season can last well over a month.

Maple trees have an early season that can occur from about the second to third week of March. The season’s can be highly effected by weather. In warm years like 2012 the season can start earlier. The main season can start from mid-March to the end of March and end mid to late May. Low to high counts are observed. Certain species are known to cause allergic reactions.

Mulberry produce very high counts at this site. The pollen season lasts approximately six weeks due to the many species present at this site. The season can start mid-April to early May and end early to late June. They are considered important allergens in high numbers.

Nettles and parietaria pollinate from late May to late September and moderate counts are observed from mid-July and into August. They are considered important allergen partly due to their small size and ability to get into the lungs.

Oak have several flowering periods which is due to the many species present. The seasons are affected by weather conditions. The season can start from the first to the third week of April and end late May to almost mid-June. The counts can get very high. Some of the species are considered highly allergenic.

Pine, fir and spruce. Some high counts are observed and the season can vary by as much as a month. The season can start from mid-April to early May and end early to late July.

Plantain pollinate from June to early October. The counts are generally in the low range and occasionally moderate. This may cause allergic reaction in highly sensitized individuals.

Poplar and aspen can have a very short season mid-March. The main season can last almost two months and can start late Marh to early April and end early to late May. Some of the counts are very high and may cause allergic reactions.

Low counts of ragweed pollen can be observed from early July. The main season usually starts late July and ends well into October when a heavy frost occurs. Moderate and high counts are obtained from the first week of August to early October. They are considered important allergens.

 Walnut are considered important in causing allergic reactions. The pollen season can start from early May to mid-May and can end late May to late June. Very high counts are observed at this site.

Pollen season lasts well over a month for  Willows. The season can start the third week of March to the third week of April and end mid to late May. Pollen levels can vary from year to year. Most years low and some moderate counts are observed. Other years the occasional high count is obtained. They can cause allergic reactions in individuals who are highly sensitized.