The woody shrub with narrow grey-green leaves known as Guayule (pronounced Gwah-yoo-lee) (Parthenium argentatum) is a Chihuahuan Desert native shrub that is somewhat of a “super” shrub, having piqued the interest of a variety of manufacturers and researchers. Guayule is a member of the Asteraceae family. Being a desert native, it is very drought-tolerant and can survive under harsh conditions, however, it requires more water than other desert natives. Guayule produces a tiny buttery yellow or cream-colored flower in the spring, and as we’ve just observed, also in the fall.
Why do we call it a “super” shrub?
A Brief History
Guayule is well-known as a source of high-quality rubber. Its use dates to the Pre-Columbian Indigenous people who made balls for games using rubber from the plant. Guayule factories sprang up in Mexico in the early 1900s, with the rubber exported to the U.S. Although there were some rubber-producing factories in California, production didn’t pick up until the need for rubber presented itself during World War II (WWII), due to supply routes in Asia having been cut off. At that time, the USDA established the Emergency Rubber Project, which included a 30,000-acre plantation of guayule. The research program ceased at the end of WWII because it was more cost-effective to import rubber from Asia. So, in 1946, when government funding ceased, Congress ordered the fields to be destroyed.
Guayule Back in the Spotlight
Since the end of WWII, the production of rubber has been dominated by businesses in Southeast Asia with rubber sourced from Hevea brasiliensis trees. Low labor costs at those businesses have made it difficult for U.S. companies to compete.
In recent years, guayule has popped back into the spotlight for two reasons:
1) A fungal infestation of Hevea trees has caused a steep drop in rubber supplies; and
2) Climate change and drought conditions in the Southwest have caused farmers to reevaluate their current crops (alfalfa and cotton) and instead look at guayule, which thrives in hot and dry conditions.
Guayule is a perennial plant. When guayule is harvested, it is cut back to the ground, but the plant remains in the ground and will grow back. For this reason, it’s an effective carbon store, retaining carbon in its root system and in the soil. It also aids in preventing erosion.
Bridgestone is but one of several companies that have bought land in Arizona and planted guayule crops in their research to commercially produce rubber for tires.
Other Uses of Guayule
Research is ongoing as to the best uses of guayule’s resin. Guayule latex is hypoallergenic, making it an important alternative for medical-quality latex gloves. The latex is said to be strong, stretchy, and soft.
When harvested, the plant’s woody stems are ground up, and the rubber and resin are extracted. The remaining product is a dry material called bagasse. This material can be made into particle board used to build furniture. Research is also ongoing regarding converting bagasse from the guayule stems to biomass.
Another area of ongoing research is the use of guayule resin as a plant-based adhesive, potentially replacing traditional wood glue. Additionally, a recent study found that argentatin-derived compounds were toxic to three types of cancer cells, while a different team of researchers is investigating the use of the resin as an insect repellent.
The guayule in the Botanical Gardens is just inside the garden gate at Marker 1, with the Desert Scrub Community. With the rainfall we’ve received this summer, we believe you’ll also discover guayule to be a beautiful little shrub.
Sources:
Guayule, a Renewable Resource for Natural Polyisoprene and Resin: Composition, Processes and Applications, Thomas Resenau, Academic Editor, January 27, 2021. https://www.mdpi.com/1420-3049/26/3/664.
