Tribulus terrestris is a deceptively lovely plant.

It fans out across surfaces with delicate fern-like leaves and, when in full bloom, displays tiny and charming yellow flowers.

Under the surface, though, this plant is a nightmare. More commonly known by names like goathead, tackweed, devil’s weed, and puncturevine, it has learned to adapt to almost any environment, pushing out native plants in its wake. It also has a myriad of defenses, making it hard to kill. Students in Rowland Hall’s fifth grade can tell you all about it. The first problem? The thorns.

“The thorns can get stuck in tires and shoes and all sorts of things,” said fifth grader August P. “It was sharp enough that it would just go through your gloved hands when you were pulling it. It went through the trash bags too.”

Hannah Blomgren got the fifth graders involved in puncturevine eradication efforts after seeing the vine’s damage on the trails along the river and realizing how perfectly the situation illustrated lessons she was teaching about the problem of invasive plants in Utah.

The roots also pose an issue. They go deep into the soil and spread around the plant in all directions. “You have to get all the roots,” said Katie P. “If you leave any of the puncturevine it’s going to regrow. It’s hard to pull it all out. Some of them were very heavy and bigger than they looked.”

The students battled the prolific and hazardous weed this fall as part of the Jordan River Commission’s puncturevine eradication efforts. Science Specialist Hannah Blomgren got the fifth graders involved after seeing the vine’s damage on the trails along the river and realizing how perfectly the situation illustrated lessons she was teaching about the problem of invasive plants in Utah.

“In fifth grade, we talk about what plants need to survive, and how invasive species use up the nutrients native plants need,” Hannah said. “We also discuss the environmental impacts involved, like erosion, especially in river areas.”

So in late September, the grade headed to Jordan Park on the west side of Salt Lake City to help remove the vines from fields and riverbanks. While working to pull the puncturevine, the students quickly learned that the tools provided to them (basic two-prong weed pullers) were not up to the task. “We noticed seeds were being left behind,” said Freya S. “We needed a machine that would pull out the roots, but then vacuum up the seeds too.”

Luckily for the students, TREC (technology, robotics, engineering, coding) teacher Kaelis Sandstrom had joined them for their field trip and was ready to help them design better tools for the job. After returning to campus, the students were given class time to build their own. Using LEGOs and basic building materials, the kids built models of their ideal puncturevine pullers. Groups came up with lots of ideas, like a puncturevine-sensing drone that could destroy the weed on sight, or a robot that looked like a small animal but was designed low to the ground to successfully get under the vines and pull them out. Since coming back from the field trip, the students have continued working on these designs in the TREC Lab on campus, working through design issues and developing new prototypes. 

They’re taking on the engineering process. They are learning you can build something really cool in a short amount of time, but in order for something to be lasting and useful, it takes time and work. And they’re learning that they can take on local problems here in Utah.—Kaelis Sandstrom, TREC teacher

“They’re taking on the engineering process,” Kaelis said. “They are learning you can build something really cool in a short amount of time, but in order for something to be lasting and useful, it takes time and work. And they’re learning that they can take on local problems here in Utah.”

Community engagement was a big reason for getting the students involved in the puncturevine eradication efforts. Part of Rowland Hall’s first strategic priority is about cultivating community partnerships, and the students did just that in a part of the city many had not visited before.

“We wanted to tie this into the idea of all of us being a part of a community or an ecosystem,” said fifth-grade teacher Samantha Hemphill. “One area where they were working was a soccer field, and so pulling out the puncturevine and helping the people who would play there made it feel important.”

In addition to the time spent working, the students also got to spend time exploring the International Peace Gardens, a site on the banks of the Jordan River that features different areas devoted to the diverse populations that call Utah home. Fifth-grade teacher Rachel Slivnick said the visit highlighted lessons the kids were learning in social studies at that time.

“We had talked a lot about the idea of windows and mirrors, learning about how their cultures can be both a window into a different way of life and also a mirror that reflects your own values and the things that are important to you,” said Rachel. “So, at the International Peace Gardens, it was almost like a scavenger hunt or a treasure hunt, identifying what makes cultures unique and how students could relate to them.”

The students aren’t done with their work along the Jordan River. In the spring they plan to return, not to pull out plants but to place new ones. They will be planting trees in the area along with their kindergarten buddies. And their impacts on the community go beyond the banks of the river. You see, puncturevine has a bounty on its leaves, and the students received two dollars a pound for the plants they pulled. A grand total of $204 will be donated to the school on their behalf, and they have lots of ideas on how it could be used.

“Maybe they use some of it for the new Upper School,” said fifth-grader Aster S.

Tribulus terrestris is a terrible plant, but Rowland Hall’s fifth grade may have helped stop its spread. At the same time, the lessons they learned planted seeds that have already grown roots, sprouted, and will continue to grow for years to come.

STEM