Junipers (cedars) are considered to be moderately allergenic (Wodehouse 1971). Juniper pollen is a major cause of seasonal allergies, but the exact number of people negatively affected by junipers is unknown. Unfortunately, it is not possible to identify the origin or species of cedar pollen (Levetin and Buck 1986) other than through the date of pollination. Regrettably, many people suffer from reactions to Ashe juniper and Eastern red-cedar (ERC) pollen.
There are five different species of junipers in Oklahoma. They are the one-seed juniper (Juniperus monosperma), redberry juniper (J. pinchotii), Rocky Mountain juniper (J. scopulorum), Ashe juniper (J. ashei) and ERC (J. virginiana). Ashe juniper and ERC are the two most common species of junipers in southern Oklahoma and north-central Texas.
In south-central Oklahoma, Ashe juniper is primarily confined to the Arbuckle Mountains. This species of juniper is far more widespread in Texas. Ashe juniper can begin to release pollen in late November and continue into January, peaking in late December. Ashe juniper pollen from southern Oklahoma and possibly Texas has been collected in Tulsa (Levetin and Buck 1986). A study conducted in Tulsa in 1985 collected Ashe juniper pollen on 67 percent of the days during a 12-day sampling period in December and 33 percent of the days sampled in January. Juniper pollen was collected 40 percent of the days in December and January surveyed from 1980 to 1985.
Eastern red-cedar is found in every state east of the Rocky Mountains. It is estimated that by 2013, ERC will cover 12.6 million acres in Oklahoma alone.
Junipers are dioecious, meaning there are male and female trees. It is estimated ERC becomes sexually mature around 10 years old. Eastern red-cedar reproduction starts with conelets developing in September on male trees. These conelets form pollen grains and turn yellowish brown, maturing during winter. During late summer and fall, green conelets begin to develop on the female trees. Conelets on the female trees open up in February, corresponding to when male trees release their pollen. Eastern red-cedar pollination during late winter through early spring is a major cause of allergy problems during this time frame. Eastern red-cedar pollen peaks during March and April in Oklahoma, and fertilization is complete by June.
New ERC seeds require approximately two months to mature; however, this may take longer depending on location. As the seeds mature, a greenish fleshy coat forms a protective berrylike cone around the seeds. These cones (berries) change colors, starting out as green, changing to white, then to blue. Each cone contains one to four seeds. There are approximately 37,000 to 43,600 seeds per pound.
If you suffer from juniper allergies, Ashe juniper probably is the cause between late December and January, and ERC is probably the cause between February and April. It is estimated that cedars are increasing in Oklahoma at a rate of 762 acres per year (Engle et al., 1996). With the number of trees increasing annually, the amount of pollen increases as well. If you or someone you know suffers from cedar allergies, do yourself and them a favor, and go cut down a few cedars today.
Engle, D. M., Bidwell, T. G., Moseley, M. E. and Masters, R. E. (1996). Invasion of Oklahoma Rangelands and Forests by Eastern Redcedar and Ashe Juniper. Oklahoma Cooperative Extension Service. Circular E-947.
Levetin, E., and Buck, P. (1986). Evidence of mountain cedar pollen in Tulsa. Annals of Allergy 56: 295-299.
Wodehouse, R. P. (1971). Hay Fever Plants. New York, Hanfer.