Cheatgrass is one of the most destructive invasive plants in the western United States. It's replaced many native grasses and herbs over millions of acres of the United States and Canada, in many places completely dominating the vegetative landscape. That's a problem because cheatgrass dies back much sooner than most of the native plants it replaces, which can leave both native grazers and livestock without anything to eat in the summer months.
What's more, by colonizing soils and leaving a large amount of dry plant material there for the summer and fall, cheatgrass provides lots of extra fuel for wildfires -- and then it comes back after those fires more easily than native grasses and herbs. And given that cheatgrass' seeds readily attach themselves burr-fashion to animal skin or clothing, they can travel easily from one place to another.
That means that it's both important and difficult to keep cheatgrass out of places it hasn't reached yet. And according to research instigated by Spokane, Washington sixth-grader Caleb Lefcort, that might even be a bit more difficult than we thought. In a new paper published in the Natural Areas Journal, Lefcort -- along with his coauthor (and dad) Hugh Lefcort -- reveal that putting your cheatgrass-seed infested hiking socks through the laundry does nothing to keep those seeds from germinating even weeks later. In other words, hikers may well be unknowingly spreading the invasive grass to new areas.
The paper, with the straightforward title "Cheatgrass (Bromus tectorum) Seeds are Still Viable after Laundry Cycle," is the result of a conversation in the Lefcort household when co-author Caleb was still a fourth-grader. In a discussion of cheatgrass burrs on socks, the elder Lefcort suggested that laundering would prevent seeds from germinating. Lefcort the younger, clearly a natural-born skeptic, suggested an experiment to test his father's hypothesis.
The pair took walks through a nearby cheatgrass-infested field wearing only socks on their feet. They then divided the socks into three groups. One group of socks was laundered with detergent, and then dried. A second group was laundered with both detergent and bleach, and then dried, while the third group remained unlaundered as a control. The laundered socks were divided into subgroups, each subgroup washed and dried in a range of different household machines with different name brand detergents.
After treatment, seeds remaining on the socks were removed and tested for germination. And that's where the surprising results occurred: even after being washed in hot water with detergent, dried, and stored for 20 days, the cheatgrass seeds showed no damage to their germinating capability.
Bleached seeds germinated after 180 days did show some overall effect: they germinated and grew more slowly than the unbleached seeds or their controls.
The study provides a bit of a reality check for those of us who may have assumed our household appliances might save us the labor of laboriously picking cheatgrass seeds off our clothing after a hike.
In California, cheatgrass can be found everywhere, though it's quite a bit less common in our hot southern deserts. The grass thrives best where it receives six inches of rain or more per year, and can form almost pure stands in the colder parts of California east of the Sierra and Cascade ranges.
The apparent impossibility of eradicating cheatgrass once it's established has been accepted wisdom almost since the grass showed up at the end of the 19th Century. In his 1949 classic "A Sand County Almanac," Aldo Leopold wrote of speaking to a California agricultural inspection officer in a Northern California stand of pure cheatgrass:
I listened carefully for clues whether the West has accepted cheat as a necessary evil, to be lived with until kingdom come, or whether it regards cheat as a challenge to rectify its past errors in land-use. I found the hopeless attitude almost universal.
That hopeless attitude may become even more universal now that it seems we may have to start burning our socks after hiking.
Then again, in a world in which sixth graders are getting good science published in peer-reviewed journals, it's kind of hard to give up hope altogether. Good work, Caleb.