Due to extreme variations in the weather, the tree pollen season fluctuates significantly from year to year. The pollen seasons described here try to cover the period of time when each can occur.
Acer sp.- Maple season varies from year to year largely due to the effect of weather. The season can occur from the end of April to the end of May with some moderate counts.
Alnus sp.- Alder season produces significant counts from the end of March to late June. The season starts from late March to mid-April and ends mid to late June. The counts fluctuate from low to high due to the number of species present and the effect of weather. The alder are considered important allergens.
Betula sp.- The birch season can start from late April to mid-May and end late May to mid-June with some very high counts observed. The season for birch varies from year to year due to the effect of weather. They are considered important allergens.
Corylus sp.- The hazelnut season can occur from early April to mid-May, depending on winter and spring conditions. The counts are in the low range and may not cause allergic reactions at these levels.
Populus sp.- The poplar, cottonwood and aspen season can start from late March to late April and end mid-May to early June. Some of the counts are very high and may cause allergic reactions.
Cupressaceae family- The cedars, junipers, and yews produce some counts from April to early July. The counts are usually low so they are probably of no significance in causing allergic reactions.
Fraxinus sp.- The ash pollen season usually lasts approximately two weeks and can begin from late April to the third week of May and end from mid-May to early June. Some moderate and low counts are observed. Considered to be allergenic only in highly sensitized individuals.
Pinaceae family- This group includes the spruce, fir and pine trees. Very high counts are observed and the pollen season can start from early May to late May and end mid-July to early August. The start and end of the season can vary by four weeks from year to year due to the effect of weather. This group is very important to those who are sensitized.
Quercus sp.- The oaks flower for a short period during the month of May. Only low counts are observed. May be of significance to those who are highly sensitized.
Ulmus sp.- The elm are important allergens. Very little pollen is collected where the sampler is located. The season can start from the second week of April to mid-May. The season can end late April to late May. The season can last from one to two weeks depending on the year.
Salix sp.- The willows season can start from mid-April to early May and end third week of May to mid-June. The season can last almost two months. There is some variation in the season from year to year due to weather and mostly moderate and low counts are observed with the rare high count.
Gramineae family- The grasses produce significant counts, mostly in the moderate range with a few high counts. The season can start mid to late june and end early October.
Ambrosia sp.- Ragweed season is from mid-August to early September with only sporadic low counts observed.
Urticaceae sp.- Nettles and parietaria occur in significant numbers that may cause allergic reactions. The season can start from mid-June to early July and end late August and the counts are generally in the low to moderate range. They are considered important allergens due to their samll size.
Artemisia sp.- The sagebrush and mugwort season is from mid-July to late September with some moderate counts observed.
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 the end of April to the end of September. Mostly moderate, with some high counts 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 May to mid-October. The counts vary from day to day, which is probably due to the effect of weather and the number of species present. Very high counts are observed from July to mid-October. They are known to cause allergic reactions.
Boletus sp.- The season for this spore is sporadic with some very high counts observed. It may be of significance in causing allergic reactions. The season is mid-June to well into October.
Coprinus sp.- This mushroom produces moderate and high counts from May to mid-October. It is considered an important allergen.
Ganoderma sp.- This bracket fungus can produce very high counts from June to well into October. 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 June to mid-October. The counts are mostly moderate with some in the high range.
Ustilaginales sp.- The allergenic properties of the smuts are unknown. The season is from May to mid-October with some very high counts from July to mid-October.
Alternaria sp.- The counts do get high and some species are known to cause allergic reactions. The season is from May 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.
Botrytis sp.- This may be a significant allergen, with mostly moderate counts. The season is June to the end of September.
Cladosporium sp.- 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.
Fusarium sp.- Counts are very sporadic throughout the whole counting season. The majority of the season occurs from May to mid-October with some high counts at this location. They are known to cause allergic reactions.
Epicoccum sp.- Some species are known to cause allergic reactions. The season, with significant counts, is from mid-July to the end of September with moderate counts.
Polythrincium sp.- The majority of the season occurs in August with mostly moderate counts.
Helicomyces sp.- Season is from mid-May to the end of September producing moderate and high counts. The season is very sporadic.
Caloplaca sp.- The season is from mid-May to the end of September. The counts are sporadic and in the low to moderate range.
Drechslera sp.- The counts are mostly in the low to moderate range. The significant counts occur from 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.
Myxomycetes- Moderate counts are observed from mid-April to mid-October. Mostly low to moderate counts are observed.
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.