The Start of Pollen Season

American elm, flowers becoming seeds in April, Homewood Cemetery (photo by Kate St. John)

14 April 2022

Have you been sneezing this week in Pittsburgh? Are your eyes itchy and watery? Pollen season just began and I can tell you which trees started it.

Pittsburgh is a deciduous place so we’re not contending with pine pollen. Instead we have wind pollinated deciduous trees that bloom before leaf out so their pollen will move freely in the forest.

When our landscape looks like this there’s pollen in the air.

The first to bloom are elms and maples.

American elms (Ulmus americana) are 100% wind pollinated and insure they don’t self-pollinate by producing female flower parts before the male parts mature. By the time the flower dangles in the wind the female parts are hidden.

The dark nobs below are pollen-loaded anthers.

American elm flowers in hand (photo by Rob Routledge, Sault College,

And there are lots of them!

The structure of sugar maple flowers (Acer saccharum) shows they’re designed for wind pollination.

Red maple flowers (Acer rubrum) are more discrete, pollinated by both wind and bees.

Red maple flowers (photo by Kate St. John)

Yesterday the temperature was warmer outside than inside so I opened the windows to pull in warm air. This morning my husband’s eyes are itchy. Uh oh. I raised the indoor pollen count. Mistake!

Spring green? Tree flowers! Ahhhh cho!

Blooming deciduous trees, Schenley Park (photo by Kate St. John)

p.s. This spring is off to a slow start so we started sneezing later than last year. 😉

(photos by Kate St. John except for elm flowers in hand by Rob Routledge, Sault College,

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