CASA GRANDE — In the arid climate of Arizona, a shrub that looks more like a weed than a traditional crop could be cultivating the answer to sustainable, natural rubber. Guayule — pronounced why-YOU-lee — produces liquid latex that can be transformed into tires, wetsuits and other everyday products.Lauren Johnson, the agricultural research director for an extraction company in Casa Grande called PanAridus, said the idea is generally to use 100 percent of the crop. The plant matter can be sold as biomass, which may be used to create particle board or energy at a biomass plant, and the resin it also produces may soon find itself in adhesive markets.Guayule has no shortage of potential, and its added sustainable nature makes it all the more attractive for further development.In this region, much of its sustainability comes out of it being a desert crop that does not need a lot of water. It needs irrigation to be productive like any other crop in Arizona, but it’s extremely tolerant of low-water conditions.On top of having lesser irrigation needs, guayule also requires less fertilizer and fewer pesticides to stay healthy. It’s a low-maintenance crop, though it does have its moments. “Of course, I make this sound easy, but it is a little bit of a finicky crop,” Johnson said. “Even with research plots, it’s easy to mess it up even though it sounds like it’s pretty low-input.”That’s mostly in the water. If a grower is looking for a medium productivity, its high tolerance lends itself to a high margin of error. But for growers looking to get a high productivity out of guayule, which typically yields relatively small amounts of rubber per plant, they have to pay a little more attention. Getting the crop ready for harvest can also take several years. Right now, the most practical and reliable way to start a crop is through transplanting, wherein it’s seeded in a greenhouse and grown plants are transported into the fields like other crops.In this context, a crop’s productivity is measured in biomass, or “just sheer quantity of stuff.”Johnson said the thing that really makes guayule interesting is its growth cycle. All the rubber is produced during its winter dormant season. The biomass may grow in spring, summer and fall, much like other crops, but once its energy is no longer put toward growth, it begins to produce rubber.With peak production around November, the time for harvest falls ideally within March. The problem is most growers need to harvest year-round to cover processing expenses.“You’re going to have to be harvesting at some far less than optimum times,” he said. “Harvesting during the summer months — you pretty much destroy the crop.”Harvesting around July and August may mean a grower gets just as much rubber out of a crop, but there’s more shrub to process, which translates to higher processing costs.Though big name companies like Bridgestone Corporation and the federal government have taken an interest, it’s still too early to tell if guayule is getting more popular and making a profitable difference for growers.“There just isn’t enough of it out there yet,” Johnson said. “It’s still really in the experimental stages, so I think we’d have to get into pilot stages and even full-scale commercial planting to really get an idea. Researchers like Johnson, though, realize it has to make money for growers before it can progress. It has to compete against crops like cotton and alfalfa, or nobody will grow it.The tire industry has a particular interest in guayule, but that has not necessarily been enough to keep research moving forward at a steady pace.In 2014 and 2015, an Arizona company called Yulex was attracting plenty of media attention sought to break the Asian rubber monopoly using gene sequencing in the odd, homegrown shrub.Jeffrey Martin, president and CEO of Yulex, told The Arizona Republic guayule could reduce the country’s reliance on foreign oil and rubber for thousands of products. He foresaw a bright future for guayule that certainly included Yulex.“For this industry to be a success, it needs many players,” he told the Republic. “The Phoenix area is becoming the epicenter for this new industry that is taking off.”Unfortunately, the industry Martin spoke so highly of in 2014 took off without his ambitious company.Johnson said Yulex recently shut down. He largely blamed its reliance on an inefficient water extraction process, which was used to create hypoallergenic latex products like medical gloves. The medical industry is still interested, but Johnson declined to go into detail. Considering how volatile the guayule business has been, it’s not hard to understand why.But as PanAridus proclaims on its website, “the race is on to utilize our planet’s resources more efficiently,” and innovative minds here in Arizona are ready to lead that charge.