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  • Paula Ogilvie

Allergies Season is Here

What’s really getting up your Nose

By Paula Ogilvie

For many people the sneezing season began in mid-to-late February when elm trees began to bloom. Didn’t see the flowers? You’re not alone. Flowers that cause allergies are greatly reduced in size and often lack petals. The male flowers produce an abundant cloud of pollen that is light, extremely tiny (microscopic) and easily carried away by wind, not insects. Plants that are insect-pollinated usually have colorful, showy flowers, often with nectar and alluring scents to attract pollinators. Wind-pollinated flowers don’t need to show off, opting for a random, blanketing pollen release instead.

Maple, cottonwood, and aspen trees are other early bloomers with wind-pollinated male flowers that release pollen and cause allergies. The white parachutes of dandelions and cottonwood trees that sail across our yards, (annoying adults but delighting the kids), carry seeds, not pollen. They aren’t making you sneeze; it’s the tiny flowers on early blooming grasses or conifer trees that you don’t see until the pollen covers your car with a fine yellow coating, so abundant that it’s visible en masse.


TV commercials mistakenly show large, colorful flowers and people running scared. But these larger flowers are pollinated by birds, bees, butterflies, and other insects, not wind. The pollen is larger, heavy, and often sticky. It needs insects to move it. If you look closely at honeybees you’ll see their legs are covered in yellow pollen which they will transfer to the next flower they visit. Lily flowers in bouquets often have the pollen bearing sacs removed to prevent accidental pollination by hand so that the blooms last longer.  Single stem lilies usually retain the sticky, yellow to rust colored pollen. Blowing on it has no effect. It isn’t the culprit for hay fever.

Grasses are an ongoing issue all summer and into fall since there are many different types — native, ornamental, and lawn. The pollen flowers are easier to see. Another culprit in late summer and fall is ragweed. Last year I observed these plants growing everywhere and some were quite robust. Ragweed stays green without much water or care, growing in vacant lots, along roadways, parks, and even in nicer yards. The allergy producing flowers aren’t obvious. Yellow sprays of goldenrod bloom at the same time and are often blamed for sneezes, but in my yard these plants are covered with a wide array of pollinators collecting pollen. No sneezing here.

It is estimated that at least 60 million people have allergies and things may be getting worse for the sufferers. Denver has always had warm days in February and March with elms and maples producing pollen flowers, but the overall warming of the climate is resulting in earlier and longer times for plants to bloom and grow. Allergy season now starts about 20 days earlier and lasts longer into the fall. Warming temperatures, increased carbon dioxide and rainfall result in more plant growth and a 20% increase in pollen. The worst areas are in the midwest and Texas, however, the rainfall in Denver varies every year and the resulting plant growth is unpredictable which can affect pollen counts here too.

Sneezing season begins with tree pollen in spring, grass pollen throughout the summer, and ragweed in the fall. So enjoy all the lovely, large, colorful flowers;  it really is ok to stop and smell the roses.


Paula Ogilvie is a former instructor of botany and biology in Denver.




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