Invasive Plant Strike Team Battles Weeds and Weather

By Tony Figueroa

Mansfield Canyon in the Santa Rita Mountains. All photos by Tony Figueroa

Tucson Audubon’s in-house Strike Team successfully completed an invasive plant treatment project in Mansfield Canyon of the Santa Rita Mountains in collaboration with Borderlands Restoration and the Coronado National Forest. Despite the amazing amount of rain this summer, the crew was able to treat invasives on about 30 acres at four disturbed hard rock mining sites and eight miles of roadside with minimal damage to non-target plants.

When we were presented with the project just north of the town of Patagonia we recognized the importance of taking on a project of scale, and its proximity to the Paton Center for Hummingbirds was additional motivation. It is part of a large-scale restoration effort being conducted by the Forest Service to improve habitat and clean up toxins leftover from mines operating in the area from the 1890s to 1940s. 

Spot treating invasive plants

Unfortunately the remediation project brought in heavy equipment that contained seeds from non-native plants from locations they had been working previously. This route of seed spread is all too familiar in non-native plant management and is something we are always trying to enlighten heavy machinery operators about. Cleaning equipment before it moves from one job site to another needs to be the standard. Otherwise, it generates new issues and additional costs for the land being restored.

There are four large restoration sites at each mine location that cover a total combined area of roughly 30 acres. We were responsible for spraying all the non-native species that grew at these sites, plus eight miles of roadsides that connect the mine locations. The list of invasives included Bermuda grass, Lehmann’s, weeping, and African lovegrasses, stink grass, crab grass, yellow bluestem, natal grass, barnyard grass, Johnson grass and Russian thistle (tumbleweed). We started herbicide treatments in late April of 2021 and finished our 5th round of operations in October.

Following 13 months of drought, we watched as the parched land at the project sites transformed during the record monsoon—it was a sight to behold. A sea of yellow and gold became hills of emerald. The work sites were mostly bare ground or heavily grazed lands prior to the rains, with no hint to what they held. But the seeds were doing what they do, waiting for precisely this moment to germinate in mass. Roadsides were soon covered in blankets of stinkgrass and other non-natives, but their populations often only went a few feet beyond the edge of the road. The great extent of the work ahead was now visible to us.

Treating heavily damaged areas

Emerging plants following the onset of rains

The record rains also made planning and execution of treatments troublesome. Our crew was fortunate to escape Temporal Gulch many times before rains made the road impassable. We persevered through the heat and the rain, and in the end we were able to complete all five rounds of treatment in the requested time. The Forest Service and Borderlands Restoration Network were thoroughly impressed with our work and end results. Tucson Audubon will be continuing invasive species treatments in the area for the next two summers in an effort to return these sites to more natural conditions for the benefit of birds and all wildlife.

Native plants flourishing in Mansfield Canyon

Tony Figueroa is Tucson Audubon’s Invasive Plant Program Manager.