Shawnee Gets Two Grass Pollen Seasons, Not One

Most allergy advice assumes one grass season. Central Oklahoma gets two. Cool-season grasses — bluegrass, fescue, timothy, rye, orchard and redtop — can start pollinating as early as late February and then stop completely after a month or two. Warm-season grasses, chiefly Bermuda along with Bahia, crabgrass and Johnson grass, start when it warms up and often do not quit until a hard freeze in November.

For a house in Shawnee, that means the practical filtration season is not "spring." It is late February through November, with only a short break. If you buy filters once a year, you are under-covered for most of it.

The acreage lots west of Shawnee mean most homes here are surrounded by warm-season grass rather than a small town lawn, and that extends the exposure well past what a filter schedule built around "spring" would cover.

Bermuda is the one that catches people out. It is the dominant lawn grass across this part of the state, it pollinates for months rather than weeks, and warm falls extend it. A homeowner who changes the filter in April and again in October has left the two heaviest Bermuda months uncovered.

If you run a media cabinet with a four- or five-inch filter, you have more capacity and can stretch intervals. On a one-inch filter through a Bermuda summer, monthly is realistic. Hold it up to a light — if you cannot see through it, it is already costing you airflow.