Predominant Pollen and Spores

Alder season can start from the third week of March to the second week of April and can end from mid-June to early July. The amount of pollen varies from year to year as well as the timing of the season. Low, moderate and high counts can be observed. The alder are considered significant allergens.

Ash pollen season lasts almost four weeks and can start mid to late April and end mid-May to early June. Moderate and high counts are observed. Considered to be allergenic in highly sensitized individuals.

Birch season can start from mid-April to early May and can end the third week of May to the third week of June. Some very high counts are observed and they are considered important allergens.

Cedars, junipers and yews produce high counts and the season can start from mid-March to eary April and end late May to mid-June. Most of the species in Canada are not considered allergenic.

Elm season can start between early to late April and end late April to second week of May. Low to high counts are observed. The season varies depending on where the sampling site is located. The elms are considered important allergens.

Grasses produce significant counts in June and July. The season can start with low counts early to mid-May and ends late September. Most of the counts are in the low to moderate range with occational high counts. The pollen levels vary from year to year.

Hazelnuts have a season lasting from one to two weeks. Mostly low counts with the occasional moderate counts possible. The season can start mid-March to early May and end from the third week of April to mid-May. Can cause allergic reactions in highly sensitized individuals.

Hemlocks can produce low and the occasional moderate counts. The season can start between mid to late May and end the third week of May to the third week of June. The season can change from year to year and lasts from one to two weeks. Some years the counts are very sporadic and very low, whereas other years the season can have low and moderate counts. May cause allergic reactions in individuals who are highly sensitized.

Maple has two distinct seasons: a short early season that may occur from mid-March to early April and the main season, that can start early April to the third week of April and end mid to late May. The season lasting well over one month. The counts can get very high and some species are known to cause allergic reactions.

Mugwort season can start from the third week of July to early August and end late September to early October with low counts observed. Could be considered an important allergen in highly sensitized individuals.

Mulberry season can be sporadic and can last almost one month. This is due to the different species present. The pollen season can start from mid-April to early May and ends mid to late May. The counts are in the low with occasional moderate counts and they may cause allergic reactions in individuals who are highly sensitized.

Nettles and parietaria produce low and some moderate counts and the season is from the third week of June to mid-September. The counts are mostly in the low range with the occasional moderate count observed. They are considered important allergens due to their small size.

Oak season can start mid-April to early May and end late May to early June. The season fluctuates in timing and the amount of pollen produced and this is mostly due to weather. The counts can reach high levels and some species can cause allergic reactions.

The season for spruce, fir and pine trees can start late April to early May and can end early to late July. Very high counts are observed during the season. This is an important group for those individuals who are sensitized.

Plantains are important allergens for highly sensitized individuals, even at low levels. The season occurs from around mid-June to mid-September.

The main season for the poplars, cottonwood and aspen can start early to mid-April and end early to late May. A short early season with low counts is possible late March to early April. The main season can last well over one month. Some of the counts are high and may cause allergic reactions.

Ragweed pollen is observed from late July to mid-October with moderate counts occurring mid-August to the third week of September. They are considered important allergens.

Sagebrush season can start from the third week of July to early August and end late September to early October with low counts observed. Could be considered an important allergen in highly sensitized individuals.

Willow season varies a great deal and can last from three to four weeks. The season can start from mid-April to the beginning of May and end mid-May to early June. Mostly low, with the occasional moderate, counts are observed. Could cause allergic reactions in highly sensitized individuals.

High counts of Alternaria are observed and certain species are known to cause allergic reactions. The season is from May to mid-October.

Aspergillus spores are found throughout the whole counting season and are probably present in significant numbers beyond that. High counts are observed from May to mid-October.

Boletus counts for this spore get very high and may be of significance in causing allergic reactions. The season is June to mid-October.

Botrytis may be a significant allergen. The season is from mid-June to mid-September with low to high counts.

Cladosporium is the most abundant spore found throughout the whole season. This spore exists all year round and high counts are known to occur from late May to well into October.

Coprinus mushroom can produce some high counts from May to mid-October. It is considered an important allergen.

Diatrypaceae counts are sporadic throughout the whole counting season. High counts can be observed from March to well into October. Not know to cause allergic reactions.

Some species of epicoccum are known to cause allergic reactions. The season with significant counts is from June to early October.

Erysiphe, also known as Powdery mildew, season with the highest counts is from May to late September. Moderate and high counts are observed.

Fusarium counts are sporadic from May to early October. Some high counts are observed.

Ganoderma or bracket fungus can produce very high counts from June to mid-October. It is considered an important allergen.

Helicomyces season is from May to the end of September producing moderate and very high counts.

Leptosphaeria season, with moderate and high counts, is from May to mid-October with great fluctuations in counts from day to day. This is probably due to the effect of weather.

Moderate counts of myxomycetes are observed from late April to late September.

Penicillium spores are found throughout the whole counting season and are probably present in significant numbers beyond that. High counts are observed from May to mid-October.

Pithomyces season is mostly in the low to moderate ranges from July to the end of September.

Uredinales or rusts do not occur in really high numbers and not enough is known about their significance in causing allergic reactions at these levels. The season, with significant counts, is from mid-May to the end of September.

Ustilaginales also know as smuts can reach high counts but allergenicity is unknown. The season is May to mid-October with some high counts.