Painted desert skies. Stark, barren landscapes. Red mountains rising like clay monuments. Few vacation spots on earth are as dramatic as the American Southwest. With the exception of agricultural areas and urban landscapes full of nonnative plants, this region’s generally sparse vegetation provides a measure of relief for the pollen-allergic all year long. Moderate to dry Southwestern winters are also largely free of the mold and mildew spores common to wet winter climates in other regions.

Spring

In the desert, springtime brings a brief frenzy of pollination. Desert grasses and trees release millions of airborne triggers. Allergenic native trees, like cottonwood, will be cresting as early as March, while April and May are peak months for grass pollens like redtop and salt grass. Ragweed pollen is unique to Arizona at this time of year, taking advantage of the warm daytime temperatures to pollinate earlier than in the rest of the country. In fact, ragweed has a very long growing season in much of the Southwest, continuing to plague travelers well into October. Although the dry deserts are not normally favored by molds, melting snow at higher elevations may encourage mold growth in the mountains.

Summer

This hot (and in southern Texas, humid) time of year is ideal for pollination. From May through September, a series of allergenic grasses and weeds fill the desert skies with airborne pollen. Ragweed, amaranth, saltbush, and sage each peak at different times throughout the summer months. Airborne particles carried by desert dust storms can also irritate the allergic traveler. Mold spores are minimal during the early part of the season, yet late summer monsoon rainfalls (especially along the Gulf Coast) bring renewed mold growth in soil and other damp places.

Fall

Most of the allergenic grasses have already come and gone by fall, so autumn belongs primarily to ragweed pollens. Amaranth is also peaking in Arizona. By late October, even the ragweed and amaranth are done, and the Southwestern skies are no longer home to native pollens. The monsoons are over, so the dryness of this region will once again keep molds at a minimum. The notable exception is agricultural areas, where rotting vegetation and harvest leftovers encourage mold and mildew. As fall winds pick up, airborne dust becomes an increasing nuisance.

Winter

Southwestern winters are generally free of native tree pollens, with the exception of tropical trees pollinating in eastern Texas. Yet the increasing use of fireplaces and wood stoves across the Southwest makes smoke a bothersome irritant. Winter air currents stagnate, creating blankets of locked-in smoke in populated rural areas, especially on designated burn days (when locals have permission to burn trash and brush on their land). The still inland air can also lock urban areas under a cloud of air pollution, irritating those sensitive to ozone and airborne chemicals.

This entry was posted on Sunday, November 18th, 2007 at 10:17 am and is filed under Seasonal & Travel. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.