How does harvesting impact White Sage (Salvia apiana) as a cultural resource in southern California?

Background/Question/Methods

Saliva apiana (White Sage) is a culturally significant plant that is endemic to southern California and the upper coastal part of Baja California.  The plant is harvested by Native Americans for cleansing and purification ceremonies and its use has expanded to New Age, Druidic, Wiccan, and other nature-centered religious groups.  This study will address concerns expressed by some members of the local Native American community that the harvesting methods used by different cultural groups are harmful to the plant. To address this question my study will examine how local communities use and harvest this plant through questionnaires and interviews, if preferred by the participant. Additionally I will perform combinations of harvest treatments on wild Salvia apiana plants.  Treatments included technique used to gather (snapping by hand, cutting with a tool, and leaf only), amount harvested (0%, 5%, 25%, 50%), and season of harvest (spring, summer).  The growth and reproduction of the plants were monitored for the remainder of the year to determine the effects of harvest.  The results of this study will be shared with both the communities involved and the scientific community.  

Results/Conclusions

Responses to treatments were dependent on site conditions.  At cooler sites (mean summer temperature below 35^oC) higher amounts of harvest resulted in a decline in plant size, while lower harvest amounts resulted in growth or no change in plant size.  At warmer sites (mean summer temperature greater than 35^oC) higher harvest amounts resulted in no change in plant size, while lower harvest amounts declined in size.  Branches that were cut or broke by hand had less continued growth than leaf only harvest regardless of site.  All treatment variables interacted to affect flowering abundance.  Plants at the coolest site that had 25% of leaves harvested, using leaf only (harvest during spring or summer) or branches snapped by hand (summer) had more flowers than the control.  Plants at the warmest site that had 50% of leaves harvested, using a cutting tool (spring or summer), leaf only (spring), and snapped by hand (summer) tended to have more flowers than the control.  Plants may be flowering more in those treatments in response to increased stress. Overall, harvesters must be aware of environmental conditions they are harvesting if they wish to collect with as little impact on the plant as possible.