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The Scourge of Central Texas Residents

Wildflower Center Volunteer Claudia Leon contributed remarkable photos and useful information on the origin of "cedar fever" now plaguing the allergic among us.

The plant which causes those annoying allergy symptoms is not actually a plant in the cedar family. It is a smallish conifer in the cypress family called Ashe juniper (Juniperus ashei). But here in the Hill Country, we often refer to it as mountain cedar, hence cedar fever.

From afar, one mountain cedar looks very much like the next. However, if you look closely you'll see some important differences. Juniperus ashei is a dioecious species with separate female and male plants.

Click on the photos below for larger versions

  • Partial view, male tree; immature cones, pollen barely visible in cones on left hand side.

  • Partial view, male tree; Close up of ripe male cones.

  • Partial view, male tree; Close up of empty cones, some pollen still clinging to scales.

  • Partial view, male tree; close up of ripening male cones, scales still tightly closed.

  • Full image of plant, gender neutral appearance of green tree.

  • Partial view, male tree; Branch with ripe male cones, strong burnt orange appearance.

  • Partial view, male tree; Close up of empty cones, frost damage evident.

  • Full image of plant, ripe male cones give tree a burnt orange tint.

  • Partial view, female tree; Branch with female cones.

  • Partial view, male tree; Branches with ripe, burnt orange colored, male cones.

  • Partial view, male tree; Branch with cones after pollen release.

  • Juniper shrub, releasing a cloud of pollen with permission, courtesy D.K.Kolshorn

Click on the photos above for larger versions

Some plants grow bluish-purple fruit cones on their branches. They are about a quarter inch in diameter and resemble the juniper "berries" we use to flavor game dishes. All the mountain cedars bearing these fruit cones are female plants, and they are not involved with the dreaded allergies at all.

To find the cedar fever culprits, you have to look at the male plants. The male plants also grow cones. These cones are smaller than the female ones, not much more than 3mm long, and they are colored burnt orange when they are ripe we are in Texas, after all! These cones look a little like miniature pinecones, carrying pollen beneath their scales.

From late December through February the pollen ripens. Usually after a cold-spell, the cone scales open to release the pollen, which is propelled by wintery high winds in big clouds of pure allergen straight to your nose. Happy sneezing and Gesundheit!!

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