Predominant Pollen and Spores

There is a short early season for alder that can occur from the second week of March to the end of March. The main season can start late March to the second week of April and end early to late June. Some high counts can be observed and can cause allergic reactions. The season can vary from year to year in counts and when the season occurs due to the effect of weather.

Ash pollen season can start early April during warm springs like 2010 and 2012. Generally the season start is from mid-April to early May and ends mid-May to early June. Some very high counts are observed. They can cause allergic reactions in highly sensitised individuals.

The season for the beech trees varies a great deal from year to year. Some years hardly any pollen is produced while other years moderate counts are possible. Generally only low counts are observed. The season can last from one week to over a month. Season start can occur from the first to the third week of May and end the third week of May to the second week of June. They may not cause reactions except in highly sensitized individuals.

Birch season can start from mid to late April and end late May to mid-June. The start and end of the season can vary from year to year by as much as two weeks based on the effect of weather. Some very high counts are observed. They are considered important allergens.

Cedar, juniper, and yew season can start early to late March and end late May to mid-June. Some very high counts are observed but most species in Canada are not considered allergenic.

Chestnut seasons vary from year to year. The season can start the second week of May to early June and end the first to last week of June. Most years only low counts are observed but moderate counts are also possible but rare.

Elm are important allergens. The season is highly affected by weather. The season can start mid-March to early April and end late April to mid-May. The amount of pollen released can vary from year to year and some years high counts are observed.

Grass season can start from early to mid-May and end mid-September to early October. Moderate and high counts are observed from mid-May to late July.

Hemlock season can vary in the amount of pollen produced, season length and when the season starts and finishes. This is due to cyclical patterns and the effect of weather. The season can start from early to late May and end late May to mid-June. Mostly low counts are observed, but the occational moderate counts are possible.

Hickory season can vary in length from one to three weeks. The seasons fluctuate a great deal from year to year. The season can start from the first week to the third week of May and end early to mid-June. The counts are mostly in the low range with some moderate counts observed some years.

Linden and basswood season varies a great deal from year to year. Some years only low counts are observed while other years moderate counts are possible. The season can start the third week of June to the second week of July and end mid to late July. The length of the season also varies from year to year.

Maple season fluctuates due to the number of species present and the effect of weather. There is a short early season that can occur from mid to late March. The main season can start from late March to almost mid-April and end mid-May to early June. Mostly low and moderate counts are observed with the occasional high counts. Some species are known to cause allergic reactions.

Mulberry season can last almost a month. The season can start mid-April to early May and end late May to early June. Mostly low, with the occational moderate, counts are observed. Can be considered allergenic in idividuals who are highly sensitized.

Nettles and parietaria occur in significant numbers that may cause allergic reactions. The season can start early to mid-June and ends late September. Mostly low and moderate counts are observed. Important allergens due to their small size.

Oak season can start the first week of April to the first week of May and end late May to mid-June. The season can vary as to when it starts but also how much pollen is produced. This is mostly due to the effect of weather. High counts are observed and some species can cause allergic reactions.

High counts of pine, fir and spruce are observed throughout the pollen season. The season start is generally from late April to the second week of May and ends early to mid-July. The pollen may cause reactions in highly sensitized individuals.

Plantains can be significant in causing allergic reactions. The season can start early to mid-June and end the second to last week of September. Only low counts are observed.

Poplar, cottonwood and aspen season can start the third week of March to early April and end early to late May. High counts are observed and allergic reactions can occur at these levels.

Ragweed pollen is observed starting the last two weeks of July with the high counts occurring from August to late September. Low pollen counts are observed until late October.They are considered to be highly allergenic.

Willows may cause allergic reactions in highly sensitized individuals. The season can start mid to late April and can end late May. Mostly low and moderate, with occasional high, counts are observed.

Some of the counts for alternaria are really high throughout the season and some species are known to cause allergic reactions. The season is from March to late October. The highest counts occur from late May to late October.

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

Boletus counts do not get very high but may be of significance in causing allergic reactions. The season is sporadic and occurs from mid-June to mid-October.

Botrytis may be a significant allergen even though the counts do not get very high. The season is from late May to mid-October.

Moderate counts are observed from August to mid-October. The season is sporadic. May not be an important allergen.

Cladosporium is the most abundant spore found throughout the whole season. This spore exists all year round and very high counts are known to occur from March to late fall.

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

Diatrypaceae spore 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 found in high numbers and some species are known to cause allergic reactions. The season is from March to late fall. The high counts occur from mid-June to late October.

Erysiphe, or powdery mildew, season occurs from April to mid-October with moderate and high counts.

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

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

Helicomyces season is from May to mid-October producing moderate and high counts. The season is very sporadic.

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

Moderate counts of myxomycetes are observed from August to mid-October.

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

Pithomyces season with high to low counts is from July to mid-October.

Allergenicity is unknown for polythrincium but significant counts are observed from July to mid-October.

Some species of torula are considered allergenic. Moderate counts are observed from July to early October.

Uredinales also know as rusts do not occur in really high numbers, but not enough is known about their significance in causing allergic reactions at these levels. The season is from mid-May to late October.

Ustilaginales or smuts can reach high counts, allergenicity is unknown. The season is mid-May to late October.