(Cedar or Red Cedar)
By: H. Wayne Shew, Ph.D.
NAB Certified Pollen Counter
Alabama Allergy & Asthma Center Collection Station—Birmingham, Alabama
Cedar is one of the first of the airborne pollens to show up every year in any significant amount in our collections. We begin to see cedar pollen in December, and depending on the weather will collect it throughout the months of January and February, and even into March and early April. The genus to which cedar belongs is Juniperus and the species that is most prevalent in this part of the U.S. is Juniperus virginiana. However, the cedar pollen that we collect in December and early January is not from this species of cedar since our cedar trees are not producing pollen during that time period. The most likely species producing the pollen we see in December and early January is mountain cedar, Juniperus ashei. This species of cedar is native to northern Mexico, and extends through Texas and into Oklahoma and Missouri. This species begins pollen production in the month of December and its pollen can be carried hundreds of miles by the wind and as a result show up in our collections. There are very large numbers of these mountain cedars in the South Central U.S., particularly Texas, and they produce hugh quantities of polen.
[efsflexvideo type=”youtube” url=”https://www.youtube.com/watch?v=7SL76MaFjJ0″ allowfullscreen=”yes” widescreen=”yes” width=”220″ height=”115″/]
Our cedar trees in this area will begin pollen production during the middle to latter part of January depending on local weather conditions. We typically begin to collect cedar pollen regularly during late January and this extends into March. We will usually collect cedar pollen in high numbers in February and in varying amounts into March. Because there are nonnative species of juniper as well as arborvitae (genus Thuja) used for landscaping in urban areas, we continue to see cedar pollen (Cupressaceae) through March and into April.
Most everyone knows what a red cedar tree looks like; the Christmas trees beside the road in this part of the Southeast. Cedars are found throughout the Southeast in a variety habitats and are often seen in large numbers in some locations, particularly over areas with limestone subsoils. These cedar glades can be seen occasionally from the interstate in various places in northern Alabama.
[efsthumbnail sdsd src=”/wp-content/uploads/2017/02/Red-cedar1-1.jpg”]
[efsthumbnail sdsd src=”/wp-content/uploads/2017/02/Red-cedar-leaves.jpg”]
Cedars belong to the plant family, Cupressaceae. This is a family of Gymnosperms that contains nineteen genera, the most familiar of which are: Chamaecyparis (white cedar), Thuja (arborvitae), Taxodium (bald cypress), Sequoia (redwood), Sequoiadendron (giant redwood), and Metasequoia (dawn redwood), as well as Juniperus. All of these plants produce pollen grains that look similar to one another and thus when we report cedar pollen it is actually listed as Cupressaceae on our NAB count sheets.
Cedar pollen is described as inaperturate because it has no opening in the wall of the pollen grain. Most plants produce pollen grains that have one or more openings in the outer wall or exine, structures called pores or colpi, and thus cedar is in a distinct minority of plant species. Cedar pollen also has a thick intine that causes the interior of the pollen grain to have a roughly star-shaped appearance, which makes cedar pollen quite distinctive when viewed under a microscope. Another feature that makes cedar pollen interesting when viewed microscopically is that the grains often burst when placed on a microscope slide in the glycerine jelly we use for mounting purposes. The burst grain resembles “Pac-Man” with the cell contents appearing like a balloon protruding from the mouth of the Pac-man figure. Sometimes the cell content is completely free of the pollen grain wall and appears as a clear, circular object on the microscope slide.
[efsthumbnail sdsd src=”https://alabamaallergy.com/wp-content/uploads/2017/02/Stacked-image-31-1024×577.jpg”]
By: H. Wayne Shew, Ph.D.
NAB certified counter
AAAC Collection Station—Birmingham, Alabama
Note: This is one of a series of blogs that describes some of the common species of plants that produce pollen in our area that are known to serve as allergens. It is a good idea to know what the plants look like that produce pollen that act as allergens and try to avoid having them around where you live if possible. You should also stay alert to when plant pollens to which you are allergic are being produced in the area where you live.