Note: this project has been updated. See 2025 Update below.
Reforestation in harsh environments is challenging. Using nurse plants to provide a microhabitat that buffers moisture and temperature extremes can allow seedlings to get established more easily. With this in mind, Dr. Ana Gabriela Zacarías-Correa, from the University of Michoacán in San Nicolás de Hidalgo, is evaluating the survival and growth of three shrub species (i.e., nurse plants) planted at three sites in the MBBR’s core zone by Dr. Cuauhtemoc Saénz and his colleagues on July, 2022.
In February 2024, Gabriela monitored the sites and found average survival for each species: 74% for coyote brush (Baccharis conferta), 63% for snakeroot (Eupatorium glabratum), and 43% for ragwort (Senecio sp.). In terms of average growth, the results were: 48.07 cm for coyote brush, 56.03 cm for snakeroot, and 70.06 cm for ragwort. Average survival through winter for each of species did not change significantly; however, snakeroot survival did decrease some likely due to this species being more sensitive to winter frost.
In September 2024, Gabriela repeated measurements and found an average survival of 69% for coyote brush (Baccharis conferta), 61% for snakeroot (Eupatorium glabratum) and 20% for ragwort (Senecio sp.), and average growth of 60 cm, 62 cm and 71 cm respectively. Nurse plants need to reach a minimum of 1 m to be useful, and these current growth measurements indicate that it will take about 4 years for coyote brush and snakeroot, and 6 years for ragwort to reach this height.
2025 Update
In her most recent measurements carried out in May 2025, average survival was 49% for coyote brush 59% for snakeroot, and 15% for ragwort, all down from previous years. Average growth for each species reached 68 cm, 72 cm, and 81 cm respectively. One of the main challenges faced this season has been drought.
Gabriela believes that shrubs currently taller than 60 cm are still excellent nurse plant candidates. She will continue to evaluate the nurse plants assessing the possibility of planting sacred fir seedlings in the 2026 rainy season.
