Mondavi, responsible for the Charles Krug brand, has been practicing sustainable winemaking techniques in Napa Valley for years. The company harvests its grapes with as much natural control as possible, and has refurbished original Charles Krug-built buildings on the winery site. Mondavi, responsible for the Charles Krug brand, has been practicing sustainable winemaking techniques in Napa Valley for years. The company harvests its grapes with as much natural control as possible, and has refurbished original Charles Krug-built buildings on the winery site.