Predominant Pollen and Spores

Alder season can start from mid-March to almost mid-April and end mid to late June. The season fluctuates from year to year and the counts are usually in the low to moderate range.

Ash season can start mid-April to early May and end mid-May to early June. High counts are observed and allergic reactions can occur in sensitized individuals.

Beech season can start late April to the second week of May and end late May to early June. The seasons fluctuate from year to year due to cyclical patterns and weather. Occasionally moderate counts can be observed but most years the counts are low. At these levels they may not cause allergenic reactions.

Birch season can start mid-March in warm years like 2010 and 2012. Generally the season start is from late March to the second week of April and ends late May to the third week of June. The counts get in the very high range. They are considered to be important allergens.

Season for the cedars, junipers, and yews can start the second week of March to early April and end late May to early June. Some high counts are observed. Most species in Canada are not considered allergenic.

Chestnut season can start from mid-May to the second week of June and end mid-June to early July. The counts are usually in the low to moderate range but some years high numbers are observed. Some of the species are considered allergenic.

Elm are important allergens. The main season can start early to mid-April and end late April to mid-May. Moderate and high counts can be observed in the main season.

Grass season can start from early to mid-May and end early October. Moderate counts are observed from late May to mid-July. This site has another season with significant counts late August to mid-September. This species of grass is unique to certain sites.

Hemlock season can vary from year to year. This is partly due to cyclical patterns and the effect of weather. Some years moderate and high counts are possible, whereas other years only sporadic low counts are observed. The season can start from early to late May and end late May to mid-June.

Season for the hickories can vary in length and pollen levels from year to year. The season can start mid-May to early June and end mid to late June. Mostly low counts are observed, but certain years moderate ones are possible.

Maple season varies due to the number of species and the effect of weather. The season can start mid-March to the second week of April and end the third week to last week of May. The counts can get in the high range and some species are considered important in causing allergic reactions.

Nettles and parietaria season can start from the first week to the last week of June and end late September. Moderate and occasionally high counts are 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 mid-June. Very high counts are observed and certain species are known to cause allergic reactions.

Season for pine, fir and spruce can start late April to mid-May and end early to mid-July. Some of the counts do get high. These are important allergens to those who have allergies to this group of trees.

Plantains can be of significance in causing allergic reactions. The season can start late June to almost mid-July and end mid-September to early October. Only low counts are observed.

Poplar, cottonwood and aspen season can start from about mid-March to early April and end early to late May. Very high counts are observed and allergic reactions can occur at these levels.

Ragweed season can start the third week of July to early August and can end late October or when there is a hard frost. Moderate and high counts occur in August and most of September.

Sagebrushes and wormwoods produce mostly low and the occasional moderate count from the first week of July to early October. May be a source of allergenicity.

Willow season can start from almost mid-April to late April and end late May to early June. Only low to moderate counts are observed so they may not cause allergic reactions except in individuals who are highly sensitized.

Alternaria counts can get really high and some species are known to cause allergic reactions. The main season is from May to late October.

Aspergillus spores are found throughout the whole counting season and are probably present in significant numbers beyond that. Significant counts are observed from March to late fall.

Boletus counts for this spore do not get very high but may be of significance in causing allergic reactions. The main season is June to mid-October.

Botrytis may be a significant allergen even though the counts do not get very high. The season is July, August and September.

Moderate counts of caloplaca occur from the end of August to mid-October. The season is sporadic and it may cause allergic reactions.

Cladosporium is the most abundant spore found throughout the whole season. This spore exists all year round but the highest counts occur from March to late fall.

Coprinus mushroom can produce high counts from May to late October. Considered an important allergen.

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

Epicoccum is not found in really high numbers but some species are known to cause allergic reactions. Season is July to late fall.

Erysiphe, also known as powdery mildew, season is from mid-April to mid-October. Significant counts are mostly in the moderate range.

Fusarium counts are very sporadic throughout the whole counting season. The majority of the season occurs from mid-June to mid-October.

Ganoderma also known as bracket fungus can produce very high counts from June to late October. Considered an important allergen.

Majority of helicomyces season is from May to the end of September.

Moderate counts of myxomycetes are observed from March to September.

Penicillium spores are found throughout the whole counting season and are probably present in significant numbers beyond that. Significant counts are observed from March to late fall.

Pithomyces season is August and September.

Allergenicity is unknown for polythrincium but significant counts are observed from the end of 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 main season is from June to late October.

Ustilaginales also know as smuts can reach high counts, but allergenicity is unknown. The season is May to late October.