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Tuesday - October 02, 2007

From: Plano, TX
Region: Southwest
Topic: Propagation
Title: Prosopsis velutina (velvet mesquite), Larrea tridentata (creosote bush), rain smell
Answered by: Nan Hampton

QUESTION:

I am an El Paso native living in Plano TX. I terribly miss the smell of rain in El Paso and have learned that this smell is due to the velvet mesquite tree and also the creosote bush, among other things. I wanted to know if these were native enough to survive in Plano, and if planting was recommended. If you have more information on what vegetation causes the wonderful smell of rain in El Paso and how I can duplicate it in my yard, I would appreciate it. Thanks.

ANSWER:

Prosopis velutina (velvet mesquite) is native to the desert areas of California, Arizona, Mexico and New Mexico—but obviously "leaks" over into Texas near El Paso. An info sheet from the AHS (American Horticultural Society) states that it does well in the USDA Plant Cold Hardiness Zones of 7-9 and the AHS Plant Heat Zones of 10-7. Plano, in zone 8 for USDA and 9 for AHS, falls well within those ranges. The range for Larrea tridentata (creosote bush) is USDA 8-11 and AHS 12-8, so it also falls within the range of Plano for temperature extremes. However, soil moisture would probably be the biggest deterrent for success of the two species in Plano since the average rainfall for Plano is 29 inches and the average rainfall for El Paso is about 9 inches. As a possible substitute, another mesquite, Prosopis glandulosa (honey mesquite), is native to the Plano area. I'm not aware, however, that it is noted for its pleasant smell after a rain. You should be aware, also, that farmers and ranchers often consider mesquites noxious weeds (even though they are native) and spend a lot of time trying to keep them under control.

In addition to the volatile oils from plants, a big contributor to the distinctive smell that comes after rain is soil bacteria. You should certainly still be able to experience this smell in Plano.

Mr. Smarty Plants has been assuming that you are talking about the distinctive smell that follows a rain, but people also report a unique smell that comes right before a rain. The smell BEFORE the rain has been attributed to a chemical called Petrichor, or in chemical terms—2-decanone. The chemicals that are constantly being volatilized and released from trees and other plants can be absorbed by rocks. The increase in humidity right before a rain has the effect of releasing these chemicals from the rock and creating the smell. Velvet mesquite and/or creosote bush must have this chemical in their makeup if they are contributing to the before-rain smell.