Sulphur cinquefoil (Potentilla recta L.) is an invasive plant of concern within grasslands in western North America. To better understand the role of native plant communities and soil seedbank in P. recta invasion within grasslands, we conducted two greenhouse studies to examine (1) P. recta growth response when grown with and without fertilizer in established native plant communities of varying functional groups (grasses, forbs, or grasses and forbs), and (2) the prevalence of P. recta and other species in the soil seedbank at varying soil depths (0 to 5 cm, 5 to 10 cm, 10 to 15 cm) of grasslands invaded by P. recta in southeastern British Columbia, Canada. The growth response of P. recta did not differ between the native plant communities. However, P. recta above- and belowground biomass declined as native plant aboveground biomass increased, suggesting a productive plant community may be important to suppress P. recta. Fertilizer did not affect the growth response of P. recta or native plants, suggesting nutrients may not have been a dominant limiting factor under greenhouse conditions. Nine species were identified in the soil seedbank. Seven were nonnative, which included P. recta, and native species represented less than 2% of the seedbank. Of the average number of emerged nonnative seedlings, more than 20% were P. recta. The number of emerged P. recta seedlings was 69% lower at 10- to 15-cm compared with 0- to 5-cm soil depth, although the successful germination of P. recta at greater soil depths suggests viable P. recta seeds are persisting in the seedbank. Active revegetation may be an important strategy to mitigate P. recta reinvasion or secondary invasion by other invasive species from the soil seedbank.

Sulphur cinquefoil (Potentilla recta L.) is an invasive perennial forb threatening rangelands in western North America. To identify best management strategies to control P. recta, we examined targeted goat (Capra hircus L.) grazing conducted once (pre-flowering) versus twice (pre-flowering and flowering and seed set), aminopyralid application, and integrated targeted grazing and aminopyralid as management strategies. We also examined the interaction between treatments and seasonality (spring and summer) and explored the possibility of off-target effects to non-target species. Two intermountain rangelands in British Columbia, Canada, were treated, one with targeted grazing treatments only and one with targeted grazing and herbicide treatments. Targeted grazing treatments were implemented in 2019 and 2020, and aminopyralid was applied once in 2019 at a rate of 56 g ai ha−1. Potentilla recta aboveground biomass and number of seed heads declined following targeted grazing treatments at both field sites in 2019 and 2020 when compared with the control, with no differences between targeted grazing treatments. In May 2020, before the implementation of targeted grazing for the second year, a decrease in P. recta biomass was not measured in the targeted grazing treatments, but biomass was 87% to 99% less in the herbicide-only and targeted grazing plus herbicide treatments. In July 2020, declines in biomass and seed heads in the herbicide-only and targeted grazing plus herbicide treatments did not differ from grazing twice, and aminopyralid effects did not differ among the three herbicide treatments. Further research is required to examine legacy effects of targeted goat grazing and aminopyralid on P. recta, establish reapplication frequency of treatments, and determine whether integrating targeted goat grazing and aminopyralid is needed in the long term to manage P. recta. A long-term study is also needed to examine off-target effects from targeted goat grazing and aminopyralid and ways to mitigate these effects to promote healthy native rangeland plant communities.