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UF/IFAS Extension University of Florida

Pollen and Allergies in Florida

A bee visiting a tiny white orange blossom with yellow pollen visible.
Plants that depend on insects for pollination for have heavy, large or sticky pollen that’s typically not allergenic. UF/IFAS

Spending time outdoors during certain times of the year can become a sniffly experience for many. The seasonal distribution of pollen, while important for plant reproduction, can be very disruptive for those with allergies. About one quarter (25.2%) of adults and one in five children (20.6%) in the United States have a seasonal allergy, according to the Center for Disease Control and Prevention (CDC)1.

Some common symptoms of allergies include watery eyes, sneezing, itching, coughing, congestion, hives, runny nose, fatigue, asthma attacks, and in rare cases, death. If you are a sufferer of seasonal allergies, or just curious, we have compiled some information about these tiny particulates.

What is pollen?

All flowering plants produce pollen, which are dust-like grains. Some pollen is visible, seen as blankets of yellow and green on cars and other surfaces. Other pollen is invisible to the naked eye, and is most likely the culprit for your allergies.

This spiky thing is a grain of pollen magnified by 2000.
A grain of pollen magnified 2,000 times with an electron microscope by UF/IFAS researchers.

These minute particles are formulated by anthers, which are the male reproductive structures of the plant. The pollen is dispersed by wind, insects, water or gravity. It eventually reaches the female reproductive structure of the flower, the pistil. The pollen then fertilizes the plant and triggers the development of seeds.

Insect-pollinated flowers do not need to produce as much pollen, because the insects are efficient at distribution. The pollen sticks to their bodies and then is transported when the insects visit other flowers. But plants that are pollinated mainly via wind will mass-produce their pollen to ensure it reaches the female flowers. As a result, their pollen is more prevalent.

In most of the United States, trees pollinate in the spring, grasses in the summer and weeds in the fall. But in Florida, we have more frequent and longer pollen seasons. Trees generally pollinate in the spring and winter, and grasses pollinate in the spring, summer and fall. Weeds may pollinate in spring, summer, fall and even in winter2.

What plants are responsible for allergies?

Not all pollen is allergenic. The kind that will cause allergic response are referred to as “botanical aeroallergens” by scientists.

A handful of brown, fallen oak flower clusters called catkins
Oak tree male flower clusters, called catkins.

The plants that produce allergenic pollen in Florida may not be what you expect. Some assume that pine tree pollen, which is known for laying on thick with yellow dust, is the cause of their sneeze attacks. On the contrary, pine tree pollen is low-allergenic. Other common trees that are unfairly blamed include mango, Brazilian pepper, palm trees and melaleuca2.

The most prevalent and highly allergenic pollen in Florida comes from a wide range of other trees, as well as grasses and weeds. Trees account for about 80% of the airborne pollen in the state, with oak (Quercus spp.) being the one of the most allergenic. February to May is peak pollinating season for the 11 species of oak in Florida, however some areas experience high pollen counts as early as December. Other tree species with highly allergenic and prevalent pollen include eastern red cedar, bald cypress, wax myrtle (also called bayberry) and the invasive Australian pine2.

Ragweed is an unassuming green weedy plant.
Common ragweed is highly allergenic. Photo: Chris Evans, University of Illinois, Bugwood.org

Grasses also play a role. Bahiagrass (Paspalum notatum), which is the most abundant grass in Florida, is high on the list of allergenic plants. Bermudagrass (which pollinates year-round in subtropical parts of the state) and Johnsongrass (Sorghum halepense) are both huge contributors to pollen allergies2.

Some weeds also have abundant, highly allergenic pollen, such as ragweed (Ambrosia spp.), the most clinically significant species. Some people mistakenly believe it’s goldenrod (Solidago spp.) that’s causing their suffering, but this plant actually has heavy, sticky pollen that does not blow in the wind (or up your nose). Other highly allergenic weeds besides ragweed include dog fennel and pigweed.

What can you do about your pollen exposure?

There are steps you can take to minimize the effects of pollen around your home. Some strategies recommended by UF/IFAS to reduce pollen exposure include:

  • Only install plants that produce pollen that is either low- or non-allergenic.
  • Dry clothes in an automatic dryer rather than hanging them outside to avoid pollen collecting on clothing and being carried indoors.
  • Consider limiting outdoor activities during the pollen season (Florida trees often release pollen from January to June).
  • Stay inside during peak pollen times (from 10 am–4 pm).
  • Restrict outdoor activities during days with high winds and low humidity.
  • Shower after spending time outdoors to remove pollen from hair and skin.
  • Use air purifiers and change their filters, as well as those in AC units, regularly.
  • Wear a dust mask when mowing the lawn, gardening or raking leaves.

Why your seasonal allergy symptoms might be getting worse

If you feel your seasonal allergy symptoms worsening over the years or lasting longer, you are not alone. Pollen seasons have become longer and more intense over the past few decades, and these trends are expected to continue. Since temperature is a factor in triggering pollen production, significant increases in global temperatures are causing pollen seasons to start earlier, making them more prolonged. Models predict that pollen emissions will increase up to 40% in the United States with increasing temperatures. Studies also suggest that increasing carbon dioxide emissions could further exacerbate the problem and trigger even more intense pollen production3.

While pollen is essential for seed production of flowering plants, it can cause significant health related issues for humans. If you are having serious allergy symptoms, see a doctor to help manage your condition.

Pollen is an interesting survival mechanism for species to carry on their lineage. Understanding where it comes from and how to reduce your exposure can give insight into living with this earthy dust-like substance.

Also on Gardening Solutions

Tree species on Gardening Solutions with their Ogren Plant-Allergy Scale (OPALS) allergenic score, where 1 is best (the most allergy-free), and 10 the most allergenic (with the highest allergy potential).

More from UF/IFAS

Resources

  1. “Almost a Third of U.S. Adults and Children Have at Least One Allergy,” U.S. Center for Disease Control’s National Center for Health Statistics
  2. Phillips, J.F., Jelks, M.L., Lockey, R.F. (2010) Important Florida botanical aeroallergens. Allergy and Asthma Proceedings, 31(4):337-40. https://doi.org/10.2500/aap.2010.31.3352
  3. Zhang, Y., Steiner, A.L. (2022) Projected climate-driven changes in pollen emission season length and magnitude over the continental United States. Nature Communications, 13, 1234. https://doi.org/10.1038/s41467-022-28764-0

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