They will also eat berries from honeysuckle, yew, Amur grapevine and buckthorn. There are thickets of bramble, hawthorn, blackthorn, dogwood, goat willow, buckthorn and dog-rose. Underbrush consists of willows, sea buckthorn, and dense growths of Indian hemp and Ural licorice. Oils from sea buckthorn seeds and pulp differ considerably in fatty acid composition. "Sap green" is a green pigment that was traditionally made of ripe buckthorn berries. Overwintering also occurs in the wetlands, where the host plant alder buckthorn is abundant. Today it has woodlands and open areas with grass and herbaceous vegetation, notably buckthorn. The species name "cathartica" and the common name "purging buckthorn" refer to this effect. Dried and ground shiny-leaf buckthorn leaves are used for fermentation. Additionally, malolactic fermentation of sea buckthorn juice reduces sourness, enhancing its sensory properties. For the compositions of sea buckthorn oils, see article&colon; sea buckthorn oil. Fruit drinks were among the earliest sea buckthorn products developed in China. It is one of three species of buckthorn that occurs without cultivation in eastern Canada. Adult common brimstones lay eggs singly on the underside of buckthorn leaves. Sea buckthorn USDA hardiness zones are about 3 through 7.