Table 2 Timing and concentration of suspect pollens and mould spores in various geographic areas across Canada [6]
Tree pollen | Grass pollen | Weed pollen | Mould spores | |
|---|---|---|---|---|
British Columbia (Coastal) | • Season: early February to mid-July • Primarily deciduous trees (alder, birch, poplar, elm, oak) | • Season: end of April to September • Highest grass concentrations: early June to mid-July | • Not usually a major factor; no native ragweed | • Levels higher in the spring; increase further in September and October • Most prevalent spores: Cladosporium and basidiomycetes |
British Columbia (Interior) | • Season: late March to mid-July • Primarily deciduous trees (willow, birch, poplar) | • Season starts in early May in southern parts of the province; starts up to 1 month later in northern parts | • Ragweed is minimal | • Cladosporium can occur from April to late fall |
Prairies | • Season starts in the first week of April and continues through June• Main deciduous trees: birch and poplar; alder, maple, elm, oak, ash, and willow may also contribute | • Season starts in mid‐May and continues to the end of September• Peak season is usually mid‐June to early July | • Most common weeds: nettles or sage brush• Some ragweed, especially in Manitoba) | • Can occur through the spring, summer, and early fall• Alternaria and Cladosporium are the predominant moulds |
Ontario and Quebec | • Season starts early April in southern Ontario and Quebec; may occur 6 weeks later in northern areas • In southern Ontario, most common are deciduous trees (birch, poplar, oak, maple, ash, elm, mulberry, willow, chestnut, hickory) • In northern Ontario, birch and poplar most common • In Quebec, ash, poplar, birch most common; maple, alder and oak are less prevalent | • Season starts mid-to-late May; a couple of weeks later in northern areas • Latter part of May and mid-June are peak seasons for grass pollination | • Ragweed season in Southern Ontario and Southwestern Quebec begins early-to-mid August • Reaches peak in late August/early September • Stops at first frost • Nettle and plantain can also contribute | • Occur during spring, summer and fall months • Concentrations may be higher late summer to fall months in Quebec • Alternaria and Cladosporium are the predominant moulds |
Maritimes | • Season in New Brunswick and Nova Scotia: late March to last week of June • Primarily deciduous trees (birch, poplar, alder, maple, oak, and ash) | • Season: mid-May to end of September • Peaks in early June | • Ragweed: early August to end of September | • Levels higher during the late summer and early fall months • Alternaria and Cladosporium are the predominant moulds |