Restoration of communities dominated by false hellebore

Abstract

False hellebore (Veratrum californicum Durand) is a native component of high-elevation, meadow-riparian areas of the mountain West that has increased due to historic heavy grazing. In 1991, a study was established in dense stands of false hellebore to evaluate mechanical and chemical control methods to reduce false hellebore and increase the abundance of the other native herbaceous species in these tall-forb communities. Four control methods consisting of the herbicide glyphosate (N-phenophonomethylglycine), mow, mowing in 2 consecutive years (remow), and tillage were used in 1991-1992. Each method was evaluated based on (1) reduction of false hellebore stem densities; (2) response of residual understory species; and (3) effectiveness of seeding a perennial grass and forb mixture to sustain initial treatment control. Stem density of false hellebore and nested frequency data for all species were collected in 1991, 1992, 1995, and 1999. The glyphosate treatment was effective in reducing false hellebore stem density which allowed for recovery of the remnant tall-forb community. The till treatment, while effectively reducing false hellebore stem density, also eliminated the other species in the community, leaving it open to invasive weeds. The mow and remow treatments did not reduce false hellebore stem density, but did allow for recovery of other components of the tall-forb community. Seeding following control treatments had no effect on false hellebore stem densities due to poor establishment. The mechanical treatments were generally more cumbersome in application and limited to gentle topography and well-drained sites without surface rocks. The application of herbicides is much easier and is adaptable to all types of terrain. The use of the herbicide glyphosate gave the best balance of false hellebore control and recovery of the tall-forb community.