Table 3 Timing and concentration of suspect pollens and mould spores in various geographic areas across Canada [6]

British Columbia (Coastal)

• Season: early February to mid-July

• Primarily alder, birch and poplar

• Others such as elm and oak may also contribute

• Season: end of April/ beginning of May to September

• Highest grass concentrations: early June to mid-July

• Not generally significant

• No native ragweed

• Present throughout the year except for few weeks when ground remains frozen all day

• Increase in September and October

• Most prevalent spores: Cladosporium and Basidiomycetes

British Columbia (Interior)

• Season: late March to mid-July

• Primarily willow, birch, and poplar

• May start in early May in Southern BC

• Occurs up to a month later in Northern BC

• Sagebrush can occur in September in Southern BC

• Ragweed is minimal

• Cladosporium can occur from April to late fall

Prairie Provinces

• Season: first week of April until June

• Primarily birch and poplar

• Alder, maple, elm, oak, ash and willow may contribute

• Season: mid-May to end of September

• Highest concentration: usually mid-June to early July

• Primarily nettles and sage brush

• Some ragweed, especially in Manitoba

• Can occur through spring, summer, and early fall (Alternaria, Cladosporium)

Ontario and Quebec

• Season starts early April in southern Ontario and Quebec; may occur 4–6 weeks later in northern parts

• In Ontario, primarily: mulberry, maple, box elder, poplar, willow, oak, beech, birch, alder, and ash; walnut, hickory, elm sycamore, pine and juniper may also contribute

• In Quebec, primarily: ash, poplar and birch; maple, alder and oak may also contribute

• Season starts mid-to-late May, a couple of weeks later in northern areas

• Highest concentration: latter part of May to mid-June

• Ragweed season in Southern Ontario and Southwestern Quebec starts from early-to-mid August

• Highest concentration: late August/early September

• Stops at first frost (variable)

• Nettle and plantain can also contribute

• Throughout spring, summer and fall months

• Concentrations may be higher late summer to fall months in Quebec

• Alternaria and Cladosporium are the predominant outdoor moulds

Maritimes & Newfoundland/

Labrador

• Season: late March to last week of June

• Primarily birch and poplar

• Alder, maple, oak and ash may also contribute

• Season: mid-May to end of September

• Highest concentration: 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