I was driving down a back road in Southern Lee County last week and slowed down when an upward glance caught on bright yellow. No, it wasn’t a stoplight that got my attention on that long stretch of road, it was the pine trees, or more specifically bright yellow pine flowers peaked to pop with pollen. The exact season start and end dates fluctuate yearly, but the yellow clouds and puddle rings sing out that pollen season is approaching.
Almost all green plants produce pollen at some time during the year, but spring is by far the time when most of the pollen is produced. The blooming trees and flowers that accompany the onset of spring and signal the beginning of pollen season can last for as much as six to eight weeks, since all plants do not develop at the same time.
Currently, the majority of the pollen count right now is not from grasses, not from weeds but from Pine and Oak trees. This information comes from the NC Division of Air Quality (DAQ) pollen sampler, located at the Laboratory Analysis Branch headquarters on Reedy Creek Road in Raleigh. Pollen reports are published daily on the DAQ pollen website (see link below). In addition to the daily pollen report, the website contains other useful pollen information such as trend graphs and historical data.
Although pine pollen is the most visible it usually doesn’t cause allergic reactions. The pollen type that affects people with allergies more severely is oak pollen, and it’s invisible to the naked eye at 24-38 micrometers (um). The smallest particles we can see with our eyes are those that are larger than 50 um. The oak trees happen to be flowering at the same time as the pine trees which is the type of pollen that’s most obvious to people. Pine pollen’s yellow cloud is a case of mistaken identity and guilt by association!
Just as plants do not develop at the same time, not all pollen looks the same – it comes in many shapes and sizes and some are a real surprise. The largest pollen is from squash: 200um. The smallest pollen is from forget-me-not flowers: 5um, -about the size of a bacteria (1-10um). The average grain of pine pollen is about 60-90 um in diameter. To put this size into perspective a dust mite is about 3 um in size, while a strand of hair is about 100 to 150 um wide.
Some factors that influence how likely a particular pollen is to cause an allergy are if they come from wind pollenated plants, and if a person has increased exposure to these plants. The amount of pollen in the atmosphere tends to be highest early in the morning on warm, dry, breezy days and lowest during chilly, wet periods. A rainy spring or late spring frost that kills flowers often reduces the amount of pollen in the atmosphere. Dry weather, nearby construction, or a group of neighboring trees competing for light, water and nutrients in the soil, can put a particular tree under stress and cause it to feel threatened. The tree reacts by trying to reproduce itself. Pollen is a byproduct of the reproductive process.
If you are interested in keeping up with the daily pollen count, take a look at https://xapps.ncdenr.org/aq/ambient/Pollen.jsp