Calgary, Alberta (City-centre)
Due to extreme variations in the weather at this site, the tree pollen season fluctuates significantly from year to year. The pollen seasons described here try to cover the time when each can occur.
Acer sp.- Maple season varies significantly from year to year due to weather. Low and Moderate counts are observed. The season starts from mid-April to early May and ends from early May to early June. The amount of pollen from the maples varies from one part of the City to the other. The amount of pollen collected at this site is much lower than at the South West Foothills location.
Alnus sp.- Alder season can start from mid to late March and ends late June to early July. The counts vary from low to moderate due to the number of species present.
Betula sp.- The birch season can begin from late April to mid-May and end early to late June. The counts do get very high. The season for birch varies from year to year due to the effect of weather.
Populus sp.- The poplar, cottonwood and aspen season can occur between late March to late May. Some of the counts are very high and may cause allergic reactions.
Cupressaceae family- The cedars, junipers and yews produce some moderate and low counts from late March to late July. Probably of no significance in causing allergic reactions except in individuals who are highly sensitized.
Fraxinus sp.- The ash pollination season can last two to four weeks. The season can begin from late April to mid-May and it can end from mid-May to mid-June. The timing, length and amount of pollen varies from year which is patially due to weather effect. Low, moderate and some high counts are observed. Considered to be allergenic only in highly sensitized individuals.
Pinaceae family- This includes the spruce, fir and pine trees. Very high counts are observed and the season occurs from early May to late July. The season start and finish varies from year to year.
Quercus sp.- The oaks flower for a short period in May or early June. Only low counts are observed. Oaks can be highly allergenic.
Ulmus sp.- The pollen season can begin from late March to late April and end late April to mid-May. The season varies from year to year due to the effect of weather and other environmental factors. The levels of pollen also vary from year to year. Some years only low counts are observed and other years moderate and the occasional high counts occur. The season lasts approximately two weeks. The elms can be considered important allergens.
Salix sp.- The willow season can start from late April to mid-May and end late May to mid-June. There is some variation in the season from year to year and low to moderate counts are observed.
Gramineae family- The grasses produce significant counts, mostly in the moderate and low ranges. The season can start from mid-May to early June and ends early October.
Ambrosia sp.- Ragweed season is from the end of July to late September with only sporadic low counts observed.
Chenopodiaceae & Amaranthaceae- This group of weeds are similar microscopically and are not differentiated. They include some weeds, which are considered allergenic. Mostly low, with the occasional moderate, counts are observed. The season starts early to mid-July and ends early October. At these levels they may not cause allergic reactions except for those who are highly sensitized and depending on the species present.
Artemisia sp.- The sagebrush season is from late July to early October with low and moderate counts observed. This group can be significant in causing allergic reactions.
Urticaceae sp.- The nettles and parietaria season is from late June to about mid-August. Most of the counts are low with only the occasional moderate one observed. Due to their small size they are considered important allergens.
Diatrypaceae sp.- The counts are sporadic throughout the whole counting season. Very high counts can be observed from late March to mid-October. They are not known to cause allergic reactions.
Erysiphe (Oospora) sp.- Powdery mildew - The season is from May to mid-October. The counts are mostly in the low and moderate ranges with some high counts observed. May not be significant in causing allergic reactions.
Leptosphaeria sp. & Leptosphaeria look-alikes- These two are grouped together since they are in the same class of fungi and are similar microscopically. The season starts May to the end of September. The counts vary from day to day, which is probably due to the effect of weather. Very high counts are observed from July to early October. They could cause allergic reactions.
Boletus sp.- The season for this spore is very sporadic with some high counts observed. It may be of significance in causing allergic reactions. The season is from late June to the end of September.
Coprinus sp.- This mushroom produces moderate and high counts from late May to early October. It is considered an important allergen.
Ganoderma sp.- The bracket fungus can produce high counts from mid-June to the end of September. It is considered an important allergen.
Uredinales sp.- The rusts do occur in very high numbers but not enough is known about their significance in causing allergic reactions at these levels. The season is from early June to mid-October. The counts are mostly low to moderate with some in the very high range.
Ustilaginales sp.- The allergenic properties of the smuts are unknown. The season is from June to mid-October with some very high counts from July to the end of September.
Alternaria sp.- The counts are in the low to moderate ranges and some species are known to cause allergic reactions. The season is from mid-April to mid-October.
Penicillium sp. & Aspergillus sp.- These spores are found throughout the whole counting season and are probably present in significant numbers beyond that. The counts are significant from March to late fall.
Botrytis sp.- This may be a significant allergen, with low to moderate counts. The season is June to the end of September.
Cladosporium sp.- Some species are known to cause allergic reactions. The most abundant spore found throughout the whole season. This spore exists all year round but very high counts are known to occur from March to well into late fall.
Epicoccum sp.- Some species are known to cause allergic reactions. The season is from late May to the end of September with only low counts. May not be a significant allergen at these levels.
Helicomyces sp.- Season is very sporadic from May to the end of September producing low to high counts.
Drechslera sp.- The counts are mostly in the low range with some moderate counts in July and August. This is a summer and fall spore, June to September. There are other related genera, which are also found in air samples, that can cause respiratory problems. One example is Bipolaris sp.
Myxomycetes- Moderate counts are observed from April to mid-October. Allergenic properties are not well known.
Last Updated: March 2015
The information presented here is designed to inform, not replace, the relationship that exists between a patient and a medical professional.