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 from year to year due to the the effect of weather. Significant counts are observed during the season which can start mid-April to early May and end late May to late June. The season lasts approximately one month. There is also a short season in early June but this species is insect pollinated and very little pollen gets airborne.
Alnus sp.- Alder season ranges from late March to late June and the counts vary from low to moderate due to the number of species present.
Betula sp.- The birch season varies a great deal from year to year due to the effect of weather. The start of the season can occur from late April to mid-May and end from the late May to late June. High counts are observed and they are considered significant allergens.
Corylus sp.- The hazelnuts produce mostly low, with the occasional moderate, counts. The season can start from early April to early May and end late April to early May. May cause allergic reactions in individuals who are highly sensitized.
Populus sp.- The poplar, cottonwood and aspen season can start from early April to late April and the end of the season can be from early May to the end of May. Because of the extreme temperatures and weather conditions the season start and finish dates can vary by as much as a month. Some of the counts are very high and may cause allergic reactions.
Cupressaceae family- The cedars, junipers and yews can produce significant counts (from low to high counts) from mid-March to late July. May not be of significance in causing allergic reactions except in highly sensitized individuals.
Fraxinus sp.- The ash pollination season can begin from late April to early May and can end mid-May to early June. The season can last at least three weeks and low to high counts are observed. Considered to be allergenic only in highly sensitized individuals.
Pinaceae family- This includes the spruce, fir and pine trees. High counts are observed and the season can start from early to late May and can end early to late July. The season varies a great deal from year to year due to the effect of weather. This is a very important group for those who are sensitised.
Quercus sp.- The oak season can start from the third week of April to the thrid week of May and end late May to mid-June. The season is highly affected by weather. Mostly low, with the occasional moderate or high, counts observed. Oaks, depending on the species, are highly allergenic.
Ulmus sp.- The elm are important allergens. Low, moderate and high counts are observed. The season can last from two to four weeks depending on the year. The pollen season can start from early April to early May and can end from early to late May.
Salix sp.- The season for willows can start from mid-April to mid-May and end late May to mid-June. There is a great variation in the season from year to year due to weather. Not only the timing of the pollen season can vary but as well the pollen levels. Some years only low counts are observed and other years very high counts are obtained. Considered to be allergenic in highly sensitized individuals.
Tilia sp.- The linden and basswood season varies from year to year. The season can start from early to mid-July and end late July to early August. Some years hardly any pollen is produced whereas other years low and moderate counts are observed. May cause allergic reactions to those who are highly sensitized.
Gramineae family- The grasses produce significant counts, usually in the moderate range, in June and July. The season can start from mid-May to early June and ends early October.
Ambrosia sp.- Ragweed season is from late July to early October. Most of the counts are low but the occasional moderate one is observed. Even at these levels ragweed can be significant in causing allergic reactions.
Urticaceae sp.- Nettles and parietaria occur in significant numbers that may cause allergic reactions and are consdered important allergens. The season start is mid-June to early July and the season end is early September. The counts are in the low to moderate ranges.
Chenopodiaceae & Amaranthaceae- These groups of weeds are similar microscopically and are not differentiated. They include some weeds which are considered allergenic. Counts are mostly in the low to moderate ranges and the occassional high count, from mid-June to early October.
Artemisia sp.- The main sagebrush and mugwort season is from mid-July to mid-October. Low to moderate counts, and the occasional high counts, are observed.
Diatrypaceae sp.- The counts are sporadic throughout the whole counting season. High counts can be observed from late March to mid-October. Not known to cause allergic reactions.
Erysiphe (Oospora) sp.- Powdery mildew - The season is from April to mid-October. Low to high counts are observed.
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 is from late March to early October. The counts vary from day to day, which is probably due to the effect of weather. Very high counts are observed from late May to mid-October.
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 mid-June to end of September.
Coprinus sp.- This mushroom can produce some very high counts in July and August. The season is from mid-May to the end of September with significant counts. It is considered an important allergen.
Ganoderma sp.- This bracket fungus can produce high counts from June to the end of September. It is considered an important allergen.
Uredinales sp.- The rusts do occur in high numbers but not enough is known about their significance in causing allergic reactions at these levels. The season is from mid-May to early October and the counts are mostly low to moderate with some in the high range.
Ustilaginales sp.- The allergenic properties of the smuts are unknown. The season is from mid-May to mid-October with some very high counts.
Alternaria sp.- The counts do get high and some species are known to cause allergic reactions. The season is from April to mid-October. The highest counts are observed from July 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. High counts are observed from March to late fall. May be considered important allergens.
Botrytis sp.- This may be a significant allergen and high counts are observed. The season is from mid-May to the end of September.
Cladosporium sp.- The most abundant spore found throughout the whole season. Some species are known to cause allergic reactions. This spore exists all year round and 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 the end of April to mid-October with low to high counts.
Fusarium sp.- Counts are very sporadic throughout the whole counting season. The majority of the season occurs from May to the end of September with mostly low to moderate counts.
Helicomyces sp.- Season is from May to the end of September, producing moderate and high counts. The season is sporadic. Allergenic properties are unknown.
Pithomyces sp.- Season is mostly in the low to moderate range, with some high counts observed, from late May to the end of September. Allergenic properties are unknown.
Caloplaca sp.- The season is from June to the end of September. The counts are sporadic and in the low to high ranges. Allergenic properties are unknown.
Drechslera sp.- The counts are in the low to moderate range. This is a summer and fall spore, July to September. There are other related genera, which are also found in air samples, that can cause respiratory problems. One example is Bipolaris sp.
Stemphylium sp.- The season occurs mostly from August to the end of September with moderate counts observed.
Myxomycetes- Moderate and low counts are observed from April to mid-October.
Last Updated: 3 March 2015
The information presented here is designed to inform, not replace, the relationship that exists between a patient and a medical professional.